acyclovir and penciclovir

The discovery of acyclovir and penciclovir has led to the development of a successful systemic therapy for treating herpes simplex virus infection and varicella-zoster virus infection, and the orally available prodrugs, valacyclovir and famciclovir, have improved antiviral treatment compliance. Acyclovir and penciclovir are phosphorylated by viral thymidine kinase and are incorporated into the DNA chain by viral DNA polymerase, resulting in chain termination. Helicase-primase plays an initial step in DNA synthesis to separate the double strand into two single strands (replication fork) and is a new target of antiviral therapy. The helicase-primase inhibitors (HPIs) pritelivir and amenamevir have novel mechanisms of action, drug resistance properties, pharmacokinetic characteristics, and clinical efficacy for treating genital herpes. The clinical study of amenamevir in herpes zoster has been completed, and amenamevir has been submitted for approval for treating herpes zoster in Japan. The clinical use of HPIs will be the beginning of a new era of anti-herpes therapy.

Topics: Acyclovir; Animals; Antiviral Agents; Clinical Trials as Topic; Guanine; Herpes Simplex; Herpes Zoster; Herpesvirus 3, Human; Humans; Oxadiazoles; Simplexvirus

This review starts with a brief description of herpes simplex virus types 1 and 2 (HSV-1 and HSV-2), the clinical diseases they cause, and the continuing clinical need for antiviral chemotherapy. A historical overview describes the progress from the early, rather toxic antivirals to acyclovir (ACV) which led the way for its prodrug, valacyclovir, to penciclovir and its prodrug, famciclovir (FCV). These compounds have been the mainstay of HSV therapy for two decades and have established a remarkable safety record. This review focuses on these compounds, the preclinical studies which reveal potentially important differences, the clinical trials, and the clinical experience through two decades. Some possible areas for further investigation are suggested. The focus shifts to new approaches and novel compounds, in particular, the combination of ACV with hydrocortisone, known as ME609 or zovirax duo, an HSV helicase-primase inhibitor, pritelivir (AIC316), and CMX001, the cidofovir prodrug for treating resistant HSV infection in immunocompromised patients. Letermovir has established that the human cytomegalovirus terminase enzyme is a valid target and that similar compounds could be sought for HSV. We discuss the difficulties facing the progression of new compounds. In our concluding remarks, we summarize the present situation including a discussion on the reclassification of FCV from prescription-only to pharmacist-controlled for herpes labialis in New Zealand in 2010; should this be repeated more widely? We conclude that HSV research is emerging from a quiescent phase.

Topics: Acyclovir; Antiviral Agents; Drug Discovery; Drug Resistance, Viral; Guanine; Herpes Simplex; Humans; Simplexvirus

Herpes simplex virus (HSV) infections can be treated efficiently by the application of antiviral drugs. The herpes family of viruses is responsible for causing a wide variety of diseases in humans. The standard therapy for the management of such infections includes acyclovir (ACV) and penciclovir (PCV) with their respective prodrugs valaciclovir and famciclovir. Though effective, long term prophylaxis with the current drugs leads to development of drug-resistant viral isolates, particularly in immunocompromised patients. Moreover, some drugs are associated with dose-limiting toxicities which limit their further utility. Therefore, there is a need to develop new antiherpetic compounds with different mechanisms of action which will be safe and effective against emerging drug resistant viral isolates. Significant advances have been made towards the design and development of novel antiviral therapeutics during the last decade. As evident by their excellent antiviral activities, pharmaceutical companies are moving forward with several new compounds into various phases of clinical trials. This review provides an overview of structure and life cycle of HSV, progress in the development of new therapies, update on the advances in emerging therapeutics under clinical development and related recent patents for the treatment of Herpes simplex virus infections.

Topics: Acyclovir; Amino Acid Sequence; Guanine; Herpes Simplex; Humans; Molecular Sequence Data; Patents as Topic; Prodrugs; Simplexvirus; Valacyclovir; Valine

Herpes simplex viruses (HSV) type 1 and type 2 are responsible for recurrent orolabial and genital infections. The standard therapy for the management of HSV infections includes acyclovir (ACV) and penciclovir (PCV) with their respective prodrugs valacyclovir and famciclovir. These compounds are phosphorylated by the viral thymidine kinase (TK) and then by cellular kinases. The triphosphate forms selectively inhibit the viral DNA polymerase (DNA pol) activity. Drug-resistant HSV isolates are frequently recovered from immunocompromised patients but rarely found in immunocompetent subjects. The gold standard phenotypic method for evaluating the susceptibility of HSV isolates to antiviral drugs is the plaque reduction assay. Plaque autoradiography allows the associated phenotype to be distinguished (TK-wild-type, TK-negative, TK-low-producer, or TK-altered viruses or mixtures of wild-type and mutant viruses). Genotypic characterization of drug-resistant isolates can reveal mutations located in the viral TK and/or in the DNA pol genes. Recombinant HSV mutants can be generated to analyze the contribution of each specific mutation with regard to the drug resistance phenotype. Most ACV-resistant mutants exhibit some reduction in their capacity to establish latency and to reactivate, as well as in their degree of neurovirulence in animal models of HSV infection. For instance, TK-negative HSV mutants establish latency with a lower efficiency than wild-type strains and reactivate poorly. DNA pol HSV mutants exhibit different degrees of attenuation of neurovirulence. The management of ACV- or PCV-resistant HSV infections includes the use of the pyrophosphate analogue foscarnet and the nucleotide analogue cidofovir. There is a need to develop new antiherpetic compounds with different mechanisms of action.

Topics: Acyclovir; Antiviral Agents; Drug Resistance, Viral; Guanine; Herpes Simplex; Herpesvirus 1, Human; Herpesvirus 2, Human; Humans; Microbial Sensitivity Tests; Mutation; Nucleosides; Prevalence; Viral Plaque Assay

Most viral diseases, with the exception of those caused by human immunodeficiency virus, are self-limited illnesses that do not require specific antiviral therapy. The currently available antiviral drugs target 3 main groups of viruses: herpes, hepatitis, and influenza viruses. With the exception of the antisense molecule fomivirsen, all antiherpes drugs inhibit viral replication by serving as competitive substrates for viral DNA polymerase. Drugs for the treatment of influenza inhibit the ion channel M(2) protein or the enzyme neuraminidase. Combination therapy with Interferon-α and ribavirin remains the backbone treatment for chronic hepatitis C; the addition of serine protease inhibitors improves the treatment outcome of patients infected with hepatitis C virus genotype 1. Chronic hepatitis B can be treated with interferon or a combination of nucleos(t)ide analogues. Notably, almost all the nucleos(t) ide analogues for the treatment of chronic hepatitis B possess anti-human immunodeficiency virus properties, and they inhibit replication of hepatitis B virus by serving as competitive substrates for its DNA polymerase. Some antiviral drugs possess multiple potential clinical applications, such as ribavirin for the treatment of chronic hepatitis C and respiratory syncytial virus and cidofovir for the treatment of cytomegalovirus and other DNA viruses. Drug resistance is an emerging threat to the clinical utility of antiviral drugs. The major mechanisms for drug resistance are mutations in the viral DNA polymerase gene or in genes that encode for the viral kinases required for the activation of certain drugs such as acyclovir and ganciclovir. Widespread antiviral resistance has limited the clinical utility of M(2) inhibitors for the prevention and treatment of influenza infections. This article provides an overview of clinically available antiviral drugs for the primary care physician, with a special focus on pharmacology, clinical uses, and adverse effects.

Topics: Acyclovir; Adenine; Amantadine; Antiviral Agents; Comorbidity; Drug Therapy, Combination; Foscarnet; Ganciclovir; Guanine; Hepatitis; Hepatitis B, Chronic; Hepatitis C; Herpesviridae Infections; HIV Infections; Humans; Influenza, Human; Interferons; Lamivudine; Nucleosides; Oligopeptides; Organophosphonates; Oseltamivir; Proline; Protease Inhibitors; Pyrimidinones; Ribavirin; Telbivudine; Thymidine; Valacyclovir; Valganciclovir; Valine; Virus Replication; Zanamivir

Topics: Acyclovir; Administration, Oral; Administration, Topical; Antiviral Agents; Guanine; Herpes Labialis; Humans; Valacyclovir; Valine

During the last three decades, a better understanding of viral replication and disease states caused by viral infections have led to the development of newer antiviral agents with enhanced activity and better tolerability. This review focuses on newer systemic and topical antiviral agents that are used in treatment of herpes viruses including herpes simplex type-1 (HSV-1) and type-2 (HSV-2), varicella-zoster virus (VZV) and cytomegalovirus CMV) as well as the human papilloma virus (HPV). Included in this article are the agents famciclovir, penciclovir, valganciclovir, imiquimod, docosanole and brivudin.

Topics: 2-Aminopurine; Acyclovir; Aminoquinolines; Antiviral Agents; Bromodeoxyuridine; Famciclovir; Fatty Alcohols; Ganciclovir; Guanine; Humans; Imiquimod; Valganciclovir; Virus Diseases

Topics: Acyclovir; Antiviral Agents; Clinical Trials as Topic; Fatty Alcohols; Guanine; Herpes Labialis; Humans; Ointments

The herpesviruses continue to produce considerable morbidity in man. Once infected with herpes simplex (HSV), the virus remains dormant within the nervous system and may reactivate if provoked by stress, trauma and/or other factors. To date, there is no cure, but antiviral medication can reduce duration and severity of symptoms and prophylaxis can suppress recurrent episodes of disease. The second-generation guanosine nucleosides, acyclovir and penciclovir, are effective inhibitors with low toxicity; both, however, have relatively low oral bioavailability. Subsequently, the orally bioavailable prodrugs valaciclovir and famciclovir have been introduced. These compounds offer high oral bioavailabilty and deliver acyclovir and penciclovir, respectively, to the target cells by means of more convenient dosing schedules. This short review points to recent experience with famciclovir in the management of HSV and varicella-zoster virus.

Topics: 2-Aminopurine; Acyclovir; Antiviral Agents; Biological Availability; Clinical Trials as Topic; Famciclovir; Guanine; Herpes Genitalis; Herpes Zoster; Humans; Male; Nervous System; Prodrugs

Acyclovir, penciclovir, and their prodrugs have been widely used during the past two decades for the treatment of herpesvirus infections. In spite of the distribution of over 2.3 x 10(6) kg of these nucleoside analogues, the prevalence of acyclovir resistance in herpes simplex virus isolates from immunocompetent hosts has remained stable at approximately 0.3%. In immuncompromised patients, in whom the risk for developing resistance is much greater, the prevalence of resistant virus has also remained stable but at a higher level, typically 4 to 7%. These observations are examined in the light of characteristics of the virus, the drugs, and host factors.

Topics: Acyclovir; Antiviral Agents; Drug Resistance, Viral; Guanine; Herpes Simplex; Humans; Microbial Sensitivity Tests; Simplexvirus

Genital herpes is one of the most widespread sexually transmitted diseases in the world. HSV2 predominates (60-80 p. 100), but the prevalence of HSV1 genital herpes is rising (20-40 p. 100). Erosive lesions of the genital organs due to HSV infection are a factor favoring HIV contamination and other sexually transmitted diseases. The main factor of transmission is asymptomatic viral excretion. Aciclovir, valaciclovir and famciclovir are effective treatment for genital herpes (primary infection, curative and preventive treatment of recurrence), but none of these compounds alters the natural history of the infection. Aciclovir given as a preventive measure reduces the load of asymptomatic viral excretion. Information and education of patients with genital herpes are key elements for prevention. Use of preservatives appears to be effective. New vaccine strategies favoring humoral and cellular response should be studied.

Topics: 2-Aminopurine; Acyclovir; Antiviral Agents; Drug Therapy, Combination; Famciclovir; Female; France; Guanine; Herpes Genitalis; Herpesvirus 1, Human; Herpesvirus 2, Human; Humans; Male; Patient Education as Topic; Risk Factors; Valacyclovir; Valine; Virus Shedding

Topics: Acyclovir; Administration, Topical; Antioxidants; Antiviral Agents; Butylated Hydroxytoluene; Drug Therapy, Combination; Guanine; Herpes Genitalis; Herpes Labialis; Herpesvirus 1, Human; Herpesvirus 2, Human; Humans; Interferon-alpha; Vidarabine

The current arsenal of antiviral agents available to the practitioner is expanding rapidly, such that by the time this article goes to press, new drugs may have already been added. Although the majority of approved drugs have been developed for use in only a few viral infections (eg, HIV, herpesviruses, and papillomavirus), discoveries made in the development of these drugs may lead to antiviral agents effective against other viruses. In addition, new uses for the currently available drugs are under evaluation. This review of antiviral agents discusses the treatments available for viral infections such as herpes simplex virus, varicella zoster virus, cytomegalovirus, human papillomavirus, chronic viral hepatitis, and others.

Topics: 2-Aminopurine; Acyclovir; Antiviral Agents; Chickenpox; Cytomegalovirus Infections; Famciclovir; Foscarnet; Guanine; Hepatitis B; Hepatitis C; Herpes Genitalis; Herpes Simplex; Herpesvirus 3, Human; Herpesvirus 8, Human; Humans; Papillomavirus Infections; Sarcoma, Kaposi; Skin Diseases, Viral; Valacyclovir; Valine

Topics: 2-Aminopurine; Acyclovir; Antiviral Agents; Child; Drug Approval; Famciclovir; Guanine; Herpesviridae Infections; Humans; Immunocompetence; United States; United States Food and Drug Administration; Valacyclovir; Valine

The antiherpes drugs, aciclovir and ganciclovir, are considered the standard treatments and prophylactic agents for infections caused by herpes simplex virus (HSV), varicella zoster virus (VZV) and cytomegalovirus (CMV). Until a decade ago, the impact of aciclovir on the control of severe and life-threatening herpesvirus infections was unprecedented. During the past few years, we have witnessed approval of new therapeutic drugs for infections caused by HSV and VZV (i.e. penciclovir and the oral prodrugs, valaciclovir and famciclovir), CMV (i.e. ganciclovir, cidofovir and fomivirsen) or HSV, VZV and CMV (i.e. foscarnet). A few agents, such as brivudin and benzimidavir, are in ongoing clinical development; others have been suspended because of safety concerns. New antiherpes agents are needed to face clinical issues such as drug resistance, increased use of antiherpes prophylaxis in transplantation and safety concerns in small children or pregnant women.

Topics: 2-Aminopurine; Acyclovir; Antiviral Agents; Arabinofuranosyluracil; Bromodeoxyuridine; Cidofovir; Clinical Trials as Topic; Cytosine; Famciclovir; Foscarnet; Ganciclovir; Guanine; Herpesviridae Infections; Humans; Organophosphonates; Organophosphorus Compounds; Thionucleotides; Valacyclovir; Valine

Topics: 2-Aminopurine; Acyclovir; Antiviral Agents; Famciclovir; Guanine; Herpes Genitalis; Herpes Labialis; Herpes Simplex; Herpes Zoster; Herpesvirus 3, Human; Humans; Immunocompromised Host; Prodrugs; Simplexvirus; Virus Replication

Several new agents for treating viral infections have been developed in recent years. All available agents are virustatic, inhibiting specific steps in the process of viral replication. No agent is active against nonreplicating or latent viruses. Acyclovir is useful in the treatment of genital herpes, herpes simplex encephalitis, mucocutaneous herpetic infection, varicella infection in the immunosuppressed host, and herpes zoster infection in the normal and the immunosuppressed host. It can also be used for prevention of herpesvirus infection in immunocompromised patients. Ganciclovir is indicated for the treatment of cytomegalovirus retinitis in patients with the acquired immunodeficiency syndrome and is effective in the treatment and prevention of cytomegalovirus infection in other immunocompromised patients. Famciclovir and valacyclovir are effective in the management of herpes simplex and varicella-zoster infection. Amantadine and rimantadine are useful therapeutically and prophylactically in the management of influenza A virus infection. Chronic hepatitis B infection can respond to lamivudine therapy, and the optimal treatment of hepatitis C is the combination of interferon alfa and ribavirin. Despite pronounced toxic effects, foscarnet and cidofovir are effective antiviral agents in specific settings.

Topics: 2-Aminopurine; Acetamides; Acyclovir; Amantadine; Antiviral Agents; Cidofovir; Cytosine; Drug Resistance, Microbial; Drugs, Investigational; Enzyme Inhibitors; Famciclovir; Foscarnet; Ganciclovir; Guanidines; Guanine; Humans; Interferons; Lamivudine; Neuraminidase; Organophosphonates; Organophosphorus Compounds; Oseltamivir; Pyrans; Ribavirin; Sialic Acids; Valacyclovir; Valine; Virus Diseases; Zanamivir

Topics: 2-Aminopurine; Acyclovir; Adrenal Cortex Hormones; Antiviral Agents; Chickenpox; Famciclovir; Guanine; Herpes Zoster; Humans; Immunocompromised Host; Prodrugs; Valacyclovir; Valine

The character of diseases caused by alphaherpesviruses has changed over the last decade. The severity of disease and the frequency of acyclovir resistance has increased with the increase in the number of immunocompromised patients. Compounding the trend towards more virulent herpes disease is the current emphasis towards outpatient management of many diseases. Much of the current antiviral research focuses on providing drugs with (i) improved oral bioavailability and pharmacokinetics which permit less frequent oral or topical dosing for suppressive treatment of herpes simplex virus (HSV) infections, (ii) different mechanisms of action for synergic effects in treating resistant HSV infections in the immunocompromised host and (iii) improved efficacy. Future antiviral agents will probably target enzymes or viral factors essential for infection or will inhibit other steps in the viral infection cycle, such as viral entry, protein synthesis or capsid assembly. Medications that augment the immune response constitute another pathway for combating herpes viral infections. Many of the newer experimental agents target essential processes unique to herpesvirus replication and, therefore, potentially have high selectivity.

Topics: 2-Aminopurine; Acyclovir; Alphaherpesvirinae; Antibodies, Monoclonal; Arabinofuranosyluracil; Cidofovir; Cytosine; Famciclovir; Guanine; Herpesviridae Infections; Humans; Organophosphonates; Organophosphorus Compounds; Valacyclovir; Valine

After several nucleoside analogues have been tested against chronic hepatitis B virus (HBV) infection with minimal success, lamivudine seems to be a highly effective new therapeutic option. This review focuses on nucleoside metabolism and on the molecular action of lamivudine as well as on results of clinical studies for several indications. We report on results of trials on the use of lamivudine for chronic HBV infection, chronic HBV under immunosuppression and prophylaxis or treatment of HBV reinfection before or after orthotopic liver transplantation. Aspects of combination therapy of different nucleoside analogues as well as on combination of lamivudine with interferon are also highlighted. Although lamivudine seems to be highly effective in most patients at the start of therapy, development of resistance by mutations in the viral polymerase is a significant clinical problem. The mode of resistance development is compared with the situation in HIV infection. Possible cross-resistance with other nucleoside analogues and the perspectives of lamivudine therapy are also considered.

Topics: 2-Aminopurine; Acyclovir; Antiviral Agents; Drug Resistance, Microbial; Drug Therapy, Combination; Famciclovir; Guanine; Hepatitis B virus; Hepatitis B, Chronic; Humans; Immunocompromised Host; Interferons; Lamivudine; Liver Transplantation; Mutation; Nucleosides; Reverse Transcriptase Inhibitors

Topics: 2-Aminopurine; Acyclovir; Antiviral Agents; Famciclovir; Guanine; Herpes Genitalis; Humans; Recurrence

Topics: 2-Aminopurine; Acyclovir; Antiviral Agents; Famciclovir; Guanine; Herpes Zoster; Herpesviridae Infections; Humans

Famciclovir is the well-absorbed oral form of penciclovir, a potent and selective antiviral agent, with activity against members of the herpesvirus family, including varicella-zoster virus (VZV), and herpes simplex virus-1 (HSV-1) and HSV-2. Famciclovir is rapidly absorbed and converted to penciclovir. Penciclovir has excellent bioavailability (77%) after oral administration of 500 mg of famciclovir. Similar to acyclovir, famciclovir is converted by phosphorylation to its active metabolite, penciclovir-triphosphate. Penciclovir-triphosphate has a prolonged in vitro intracellular half-life of 10 to 20 hours in HSV-1-and HSV-2-infected cells, respectively, and 9 to 14 hours in VZV-infected cells. In contrast, the in vitro intracellular half-life of acyclovir is substantially shorter at 0.7 and 1 hours in HSV-1- and HSV-2-infected cells, respectively, and 0.8 hours in VZV-infected cells. Famciclovir is eliminated primarily via the kidneys. Dosage adjustment is not required for famciclovir in elderly patients with normal or mildly impaired renal function, and the extent of penciclovir availability is not affected by food. The excellent bioavailability ensures that adequate drug reaches virus-infected cells, and the prolonged intracellular half-life of the active form of famciclovir results in persistent antiviral activity.

Topics: 2-Aminopurine; Acyclovir; Aged; Antiviral Agents; Drug Interactions; Famciclovir; Guanine; Herpes Zoster; Humans

During the past decade, potent agents against herpes simplex virus (HSV) types 1 and 2, varicella zoster virus (VZV), and cytomegalovirus (CMV) have become available. The increasing clinical use of acyclovir, ganciclovir, and foscarnet has been associated with the emergence of drug-resistant herpesvirus strains. Resistance to acyclovir or ganciclovir most frequently results from deficient intracellular phosphorylation of these agents which is required for drug activation. Resistance to foscarnet is due to viral DNA polymerase mutants that permit viral replication despite the presence of the drug. In immunocompetent patients, herpesvirus resistance is rare and generally does not correlate with clinical outcome. In contrast, in immunocompromised hosts, resistance of HSV, VZV, and CMV is increasingly detected, and may be associated with disease refractory to antiviral therapy. Foscarnet treatment has been used with some clinical benefit in patients with acyclovir-resistant HSV or VZV, or ganciclovir-resistant CMV. For therapy of resistant mucocutaneous HSV disease, topical trifluorothymidine, and topical or intravenous cidofovir (HPMPC) have yielded encouraging results that warrant further investigation. Improved methods for detection of herpesvirus resistance, and validation of alternative therapy for patients with documented resistance are required to reduce the clinical impact of drug-resistant herpesviruses.

Topics: 2-Aminopurine; Acyclovir; Antiviral Agents; Cidofovir; Cytosine; Drug Resistance, Microbial; Famciclovir; Foscarnet; Ganciclovir; Guanine; Herpesviridae; Herpesviridae Infections; Humans; Immunocompromised Host; Organophosphonates; Organophosphorus Compounds; Valacyclovir; Valine

Valaciclovir and famciclovir, two new prodrugs (for aciclovir and penciclovir, respectively) have similar pharmacokinetics in many regards. Both have good but incomplete bioavailability, with the conversion to the active forms taking place in the liver, but by different cytosolic enzymes. Absorption and conversion are consistent in relevant patient groups, including those with liver disease. The pharmacokinetics of both active molecules are also similar in being mainly renally eliminated, a significant component of which is tubular secretion, and elimination half-lives from plasma of approximately 2.2 to 2.5 hours. Dosage adjustment is required in the presence of renal impairment. No clinically important drug interactions have been identified with either drug. The choice between the two agents is likely to depend on clinical factors such as tolerability, safety, efficacy, compliance and possibly cost, rather than on their pharmacokinetics.

Topics: 2-Aminopurine; Acyclovir; Animals; Antiviral Agents; Famciclovir; Guanine; Herpesviridae Infections; Humans; Prodrugs; Valacyclovir; Valine

Over the past 15 years, acyclovir has become established as standard therapy for the management of herpes simplex virus infections, but there are areas where improvements might be made. Acyclovir has a relatively low oral bioavailability. As a result, valaciclovir, the L-valine ester of acyclovir, is being developed. This new drug produces enhanced plasma levels of acyclovir following oral dosing, which will not only allow more convenient dosing for the treatment of herpes simplex virus and varicella zoster virus (VZV) infections, but also mean that valaciclovir has the potential for superior clinical efficacy over acyclovir. This may broaden the potential utility of the drug to include human cytomegalovirus prophylaxis. Other new drugs in the antiherpes area include penciclovir and its pro-drug famciclovir, which have antiviral characteristics similar to acyclovir but no clinical benefit over and above that seen with acyclovir has been demonstrated. The synthesis of new specific antiherpes compounds has led to the discovery of a novel nucleoside analogue, 882C87, which has significantly greater activity against VZV than acyclovir. The compound also has a longer plasma half-life than acyclovir which may permit less frequent dosing.

Topics: Acyclovir; Arabinofuranosyluracil; Cytomegalovirus Infections; Ganciclovir; Guanine; Herpes Simplex; Herpesvirus 3, Human; Humans; Valacyclovir; Valine

OBJECTIVES To determine, following oral administration of famciclovir, pharmacokinetic (PK) parameters for 2 of its metabolites (penciclovir and BRL42359) in plasma and tears of healthy cats so that famciclovir dosage recommendations for the treatment of herpetic disease can be optimized. ANIMALS 7 male domestic shorthair cats. PROCEDURES In a crossover study, each of 3 doses of famciclovir (30, 40, or 90 mg/kg) was administered every 8 or 12 hours for 3 days. Six cats were randomly assigned to each dosage regimen. Plasma and tear samples were obtained at predetermined times after famciclovir administration. Pharmacokinetic parameters were determined for BRL42359 and penciclovir by compartmental and noncompartmental methods. Pharmacokinetic-pharmacodynamic (PK-PD) indices were determined for penciclovir and compared among all dosage regimens. RESULTS Compared with penciclovir concentrations, BRL42359 concentrations were 5- to 11-fold greater in plasma and 4- to 7-fold greater in tears. Pharmacokinetic parameters and PK-PD indices for the 90 mg/kg regimens were superior to those for the 30 and 40 mg/kg regimens, regardless of dosing frequency. Penciclovir concentrations in tears ranged from 18% to 25% of those in plasma. Administration of 30 or 40 mg/kg every 8 hours achieved penciclovir concentrations likely to be therapeutic in plasma but not in tears. Penciclovir concentrations likely to be therapeutic in tears were achieved only with the two 90 mg/kg regimens. CONCLUSIONS AND CLINICAL RELEVANCE In cats, famciclovir absorption is variable and its metabolism saturable. Conversion of BRL42359 to penciclovir is rate limiting. The recommended dosage of famciclovir is 90 mg/kg every 12 hours for cats infected with feline herpesvirus.

Topics: 2-Aminopurine; Acyclovir; Administration, Oral; Animals; Antiviral Agents; Area Under Curve; Cats; Cross-Over Studies; Dose-Response Relationship, Drug; Famciclovir; Guanine; Male; Specific Pathogen-Free Organisms; Tears

To validate a means of collecting tears from cats, develop an assay for quantifying famciclovir and penciclovir in tears, and to assess famciclovir and penciclovir concentrations and pharmacokinetics in the tears of cats being treated orally with famciclovir for suspected herpetic disease.. Seven client-owned cats.. Cats were treated orally with a median (range) dose of 40 (39-72) mg of famciclovir/kg three times daily for at least 24 h. At various time points following famciclovir administration, tear samples were collected using Schirmer tear test strips. Tear famciclovir and penciclovir concentrations were measured using liquid chromatography-mass spectrometry, and concentration-time profiles were analyzed noncompartmentally. The relationship between famciclovir dose and tear penciclovir concentration near its maximum was evaluated using least squares linear regression.. Maximum tear famciclovir concentration of 0.305 μg/mL occurred at 2.64 h; elimination half-life was 2.28 h. Maximum tear penciclovir concentration (0.981 μg/mL) occurred 2.25 h following oral administration of famciclovir; elimination half-life was 2.77 h. A significant positive correlation was noted between famciclovir dose and tear penciclovir concentration at various time points between 0.5 and 3.75 h following drug administration (P = 0.025). Tear penciclovir concentration exceeded the concentration shown to have in vitro efficacy against feline herpesvirus (FHV-1) (0.304 μg/mL) in about half of samples collected.. Oral administration of 40 mg of famciclovir/kg to cats resulted in a tear penciclovir concentration-time profile that approximated the plasma penciclovir concentration-time profile and frequently achieved a penciclovir concentration at the ocular surface likely to be effective against FHV-1.

Topics: 2-Aminopurine; Acyclovir; Administration, Oral; Animals; Antiviral Agents; Cats; Dose-Response Relationship, Drug; Eye Diseases; Famciclovir; Guanine; Herpesviridae Infections; Pilot Projects; Specimen Handling; Tears

A multicenter, open-label study evaluated the single-dose pharmacokinetics and safety of a pediatric oral famciclovir (prodrug of penciclovir) formulation in infants aged 1 to 12 months with suspicion or evidence of herpes simplex virus infection. Individualized single doses of famciclovir based on the infant's body weight ranged from 25 to 175 mg. Eighteen infants were enrolled (1 to <3 months old [n = 8], 3 to <6 months old [n = 5], and 6 to 12 months old [n = 5]). Seventeen infants were included in the pharmacokinetic analysis; one infant experienced immediate emesis and was excluded. Mean C(max) and AUC(0-6) values of penciclovir in infants <6 months of age were approximately 3- to 4-fold lower than those in the 6- to 12-month age group. Specifically, mean AUC(0-6) was 2.2 microg h/ml in infants aged 1 to <3 months, 3.2 microg h/ml in infants aged 3 to <6 months, and 8.8 microg h/ml in infants aged 6 to 12 months. These data suggested that the dose administered to infants <6 months was less than optimal. Eight (44.4%) infants experienced at least one adverse event with gastrointestinal events reported most commonly. An updated pharmacokinetic analysis was conducted, which incorporated the data in infants from the present study and previously published data on children 1 to 12 years of age. An eight-step dosing regimen was derived that targeted exposure in infants and children 6 months to 12 years of age to match the penciclovir AUC seen in adults after a 500-mg dose of famciclovir.

Topics: 2-Aminopurine; Acyclovir; Administration, Oral; Antiviral Agents; Body Weight; Capsules; Child; Child, Preschool; Famciclovir; Female; Guanine; Herpes Simplex; Humans; Infant, Newborn; Male; Models, Biological

The aim of this study was to present a new topical treatment protocol for oral hairy leukoplakia (OHL), consisting of a 25% podophyllin resin with a 1% penciclovir cream (PP), and to compare this topical treatment protocol's efficacy with that of 2 other topical treatment protocols: a 25% podophyllin resin (P) and a 25% podophyllin resin with a 5% acyclovir cream (PA).. Forty-two human immunodeficiency virus-positive patients with 69 OHL lesions were randomly treated using P, PA, or PP (14 patients in each topical treatment protocol). Clinical healing was determined when the white plaque could no longer be seen in the primary location of the lesion. Topical treatment performance was evaluated by clinical healing within each week of topical treatment protocol as well as by the recurrence of the lesion. Statistical survival analysis was performed using a Cox proportional hazards model.. Approximately 55% of the patients presented with clinical healing of OHL within 7-8 weeks of each topical treatment protocol. After the sixth week, the PA treatment protocol presented a faster clinical healing rate of OHL. Recurrence was observed in 3 and 7 OHL lesions treated with P and PP treatment protocols, respectively.. The PP treatment protocol proved to be effective; however, the PA treatment protocol was more effective in the clinical healing rate for OHL than P and PP after the sixth week of treatment, and no recurrent OHL was observed in the PA treatment group.

Topics: Acyclovir; Administration, Topical; Adult; Antifungal Agents; Antineoplastic Agents, Phytogenic; Antiviral Agents; Candidiasis, Oral; Double-Blind Method; Female; Follow-Up Studies; Guanine; Heterosexuality; HIV Infections; HIV Seropositivity; Humans; Leukoplakia, Hairy; Male; Middle Aged; Neoplasm Recurrence, Local; Podophyllin; Proportional Hazards Models; Remission Induction; Time Factors; Tongue Neoplasms; Treatment Outcome; Young Adult

To investigate penciclovir pharmacokinetics following single and multiple oral administrations of famciclovir to cats.. 8 adult cats.. A balanced crossover design was used. Phase I consisted of a single administration (62.5 mg, PO) of famciclovir. Phase II consisted of multiple doses of famciclovir (62.5 mg, PO) given every 8 or 12 hours for 3 days. Plasma penciclovir concentrations were assayed via liquid chromatography-mass spectrometry at fixed time points after famciclovir administration.. Following a single dose of famciclovir, the dose-normalized (15 mg/kg) maximum concentration (C(max)) of penciclovir (350 +/- 180 ng/mL) occurred at 4.6 +/- 1.8 hours and mean +/- SD apparent elimination half-life was 3.1 +/- 0.9 hours. However, the dose-normalized area under the plasma penciclovir concentration-time curve extrapolated to infinity (AUC(0-->)) during phase I decreased with increasing dose, suggesting either nonlinear pharmacokinetics or interindividual variability among cats. Accumulation occurred following multiple doses of famciclovir administered every 8 hours as indicated by a significantly increased dose-normalized AUC, compared with AUC(0-->) from phase 1. Dose-normalized penciclovir C(max)following administration of famciclovir every 12 or 8 hours (290 +/- 150 ng/mL or 780 +/- 250 ng/mL, respectively) was notably less than the in vitro concentration (3,500 ng/mL) required for activity against feline herpesvirus-1.. Penciclovir pharmacokinetics following oral famciclovir administration in cats appeared complex within the dosage range studied. Famciclovir dosages of 15 mg/kg administered every 8 hours to cats are unlikely to result in plasma penciclovir concentrations with activity against feline herpesvirus-1.

Topics: 2-Aminopurine; Acyclovir; Administration, Oral; Animals; Antiviral Agents; Area Under Curve; Cats; Cross-Over Studies; Drug Interactions; Famciclovir; Female; Guanine; Half-Life; Prodrugs; Specific Pathogen-Free Organisms

Subjects received topical penciclovir for 4 days during successive episodes of recurrent herpes labialis. Isolation of herpes simplex virus (HSV) was attempted from lesions obtained before initiation of treatment and on each day of therapy. Isolates remained sensitive to penciclovir when tested by a plaque reduction assay, and there was no significant change in sensitivity during any treatment course or between successive treatments. The proportion of nucleoside-resistant variants present within a subset of these isolates was further investigated using a more-sensitive plating efficiency assay. Although the proportion of antiviral-resistant HSV variants increased on successive days, it invariably remained a minor subpopulation. Moreover, isolates from successive episodes obtained before treatment showed no change in the proportion of resistant HSV variants. We conclude that antiviral-resistant variants, which are readily detected in HSV isolates from peripheral lesions, do not accumulate in the sensory ganglia of immunocompetent patients receiving multiple courses of nucleoside analogues.

Topics: Acyclovir; Adolescent; Adult; Antiviral Agents; Drug Resistance, Viral; Female; Guanine; Herpes Labialis; Herpesvirus 1, Human; Humans; Male; Time Factors; Viral Plaque Assay

Asusceptibility testing program was established to determine the prevalence of resistance to penciclovir among herpes simplex virus isolates collected from patients participating in 11 world-wide clinical trials involving penciclovir (topical or intravenous formulations) or famciclovir, the oral prodrug of penciclovir. These trials represented nine randomised double blind, placebo or aciclovir-controlled studies and two open-label studies. Groups surveyed included immunocompetent or immunocompromised patients receiving 2 to 12 months chronic suppressive therapy for genital herpes, immunocompetent patients with recurrent herpes labialis treated for four days, and immunocompromised patients with mucocutaneous herpes simplex virus (HSV). Another subset of patients had been identified as non-responders to aciclovir or to valaciclovir. This program assessed the susceptibility profile for a total of 2145 herpes simplex virus isolates from 913 immunocompetent and 288 immunocompromised patients treated with penciclovir, famciclovir, aciclovir or placebo (depending on trial design). HSV isolates were tested for susceptibility to penciclovir using the plaque reduction assay (PRA) in MRC-5 cells. Resistance was defined as an IC(50)>or=2.0 microg/ml or an IC(50)> 10-fold above the wild type control virus IC(50) within that particular assay. Penciclovir-resistant HSV was isolated from 0.22% immunocompetent patients, and 2.1% of immunocompromised patients overall and therefore the frequency of penciclovir-resistant herpes simplex virus in the immunocompetent population approximates that of aciclovir-resistant herpesvirus reported previously. Penciclovir-resistant HSV isolates were more common in isolates from immunocompromised patients, consistent with aciclovir clinical experience. Treatment with penciclovir (intravenous formulation) was associated with the development of resistant HSV in only one severely immunocompromised patient (day 7 isolate IC(50) = 2.01 microg/ml), although treatment was effective and resulted in the complete clearance of the lesion by day 8. No patients receiving topical penciclovir developed treatment-associated penciclovir-resistant HSV, and a single immunocompromised patient developed resistant HSV upon treatment with oral famiciclovir.

Topics: Acyclovir; Antiviral Agents; Clinical Trials as Topic; Drug Resistance, Viral; Guanine; Humans; Immunocompetence; Immunocompromised Host; Microbial Sensitivity Tests; Simplexvirus

Two randomized, double-blind, parallel-group clinical trials were conducted in Europe and North America to compare the efficacy and safety of topical 1 percent penciclovir cream with a placebo cream.. A total of 4,573 immunocompetent people with a history of recurrent herpes simplex labialis, or HSL, with three or more episodes a year that typically manifested as classical lesions, were enrolled and prospectively dispensed medication-either 1 percent penciclovir in a cetomacrogol cream base or a matching placebo. Patients self-initiated treatment and were required to apply study medication six times per day for the first day and every two hours while awake for four consecutive days.. Of 4,573 enrolled patients, 3,057 initiated treatment (1,516 with penciclovir and 1,541 with placebo). Combined data from two trials revealed that penciclovir recipients lost classical lesions 31 percent faster than did placebo recipients (hazard ratio, or HR, = 1.31; 95 percent confidence interval, or CI, 1.20 to 1.42; P = .0001) and experienced 28 percent faster resolution of lesion pain (HR = 1.28; 95 percent CI, 1.17 to 1.39; P = .0001). Significant benefits were achieved with penciclovir use whether treatment was initiated in the early stages (P = .001) or later stages (P = .0055).. The largest data set currently available on the treatment of recurrent HSL revealed that penciclovir cream significantly outperformed the placebo in healing classical lesions and resolution of pain.. The authors found that penciclovir cream positively affects recurrent HSL, and dose frequency is vital to topical treatment. Even when penciclovir was applied late, it was effective in favorably altering the course of recurrent HSL.

Topics: Acyclovir; Administration, Topical; Adolescent; Adult; Aged; Aged, 80 and over; Antiviral Agents; Confidence Intervals; Double-Blind Method; Female; Guanine; Herpes Labialis; Humans; Male; Middle Aged; Odds Ratio; Ointments; Placebos; Proportional Hazards Models; Prospective Studies; Recurrence; Reverse Transcriptase Inhibitors; Safety; Statistics, Nonparametric; Time Factors; Treatment Outcome; Virus Shedding; Wound Healing

Herpes simplex facialis/labialis (HSFL) is a common infectious skin disorder, caused mainly by herpes simplex virus (HSV) type 1, for which the topical application of a cream containing an antiviral agent for treatment of the disease has been widely utilized.. To explore the efficacy of the topical application of 1% penciclovir cream in the treatment of HSFL, and to compare its efficacy and safety with 3% aciclovir cream.. A total of 248 patients with a diagnosis of HSFL were randomly allocated to one of the two treatment groups (n = 124 each), using stratified randomization based on a table of random numbers. Before treatment (day 0) and at every visit (days 3, 5 and 7) during the study, the sign and symptom scores were recorded by the same doctor.. Excluding 23 patients (10 in the penciclovir and 13 in the aciclovir groups), 225 completed the study, and no severe adverse events were noted with any of the treatment regimens. Results show that an encouraging improvement in the clinical course was found simultaneously for patients with each episode type and each treatment assignment. There were no significant differences in terms of efficacy endpoint, clinical cure rate, and safety between the two treatment arms, but there was a trend towards a shorter time to resolution of all symptoms, cessation of new blisters, and loss of crust (p

Topics: Acyclovir; Administration, Cutaneous; Adolescent; Adult; Aged; Antiviral Agents; Double-Blind Method; Drug Administration Schedule; Facial Dermatoses; Female; Guanine; Herpes Labialis; Herpes Simplex; Humans; Male; Middle Aged; Ointments; Pruritus; Treatment Outcome

Acyclovir cream has been available for the treatment of herpes labialis in numerous countries outside the United States for over a decade. Evidence for its efficacy comes from a few small clinical trials conducted in the 1980s. To examine more comprehensively the efficacy and safety of this formulation, we conducted two independent, identical, parallel, randomized, double-blind, vehicle-controlled, large-scale multicenter clinical trials. Healthy adults with a history of frequent herpes labialis were recruited from the general population, screened for eligibility, randomized equally to 5% acyclovir cream or vehicle control, given study medication, and told to self-initiate treatment five times daily for 4 days beginning within 1 h of the onset of a recurrent episode. The number of patients who treated a lesion was 686 in study 1 and 699 in study 2. In study 1, the mean duration of episodes was 4.3 days for patients treated with acyclovir cream and 4.8 days for those treated with the vehicle control (hazards ratio [HR] = 1.23; 95% confidence interval [CI], 1.06 to 1.44; P = 0.007). In study 2, the mean duration of episodes was 4.6 days for patients treated with acyclovir cream and 5.2 days for those treated with the vehicle control (HR = 1.24; 95% CI, 1.06 to 1.44; P = 0.006). Efficacy was apparent whether therapy was initiated "early" (prodrome or erythema lesion stage) or "late" (papule or vesicle stage). There was a statistically significant reduction in the duration of lesion pain in both studies. Acyclovir cream did not prevent the development of classical lesions (progression to vesicles, ulcers, and/or crusts). Adverse events were mild and infrequent.

Topics: Acyclovir; Adolescent; Adult; Aged; Aged, 80 and over; Antiviral Agents; Double-Blind Method; Female; Guanine; Herpes Labialis; Humans; Idoxuridine; Male; Middle Aged; Ointments; Pharmaceutical Vehicles

This study compares the effects of topical acyclovir and penciclovir in the treatment of recurrent herpes labialis. The study patients were a population of 40 patients with in excess of five recurrences annually, and were separated into four homogeneous groups each of 10 subjects. The antiviral creams were used to achieve total lesional cover, every 2 h during waking hours. The effects on the time to lesion crusting and to resolution of pain, were assessed. The results not only confirmed that aciclovir is ineffective, but confirmed that penciclovir is effective, and that penciclovir is superior to aciclovir.

Topics: Acyclovir; Administration, Topical; Adolescent; Adult; Antiviral Agents; Child; Female; Guanine; Herpes Labialis; Humans; Male; Middle Aged

The purpose of this study was to further define the therapeutic value of penciclovir cream in the treatment of sunlight-induced herpes labialis by comparing its efficacy and tolerability with those of an inactive control (purified water).. In this randomized, double-blind, placebo-controlled, parallel-group clinical trial, lesions were induced by exposure to sunlight. Treatment was self-initiated within 1 hour of development of the signs or symptoms of a recurrence.. Healthy male and female patients (mean age, 38.3 years; range, 18 to 81 years) who had a history of sunlight-induced herpes labialis (mean of 6 recurrences in previous 12 months) applied either penciclovir cream (n = 266) or purified water (n = 275). Penciclovir cream significantly decreased the time to lesion healing (P < 0.001), with a reduction in median time of up to 2 days. The efficacy of penciclovir cream was further supported by a significant reduction in maximum lesion area (P = 0.008), a faster loss of lesion-associated symptoms (P = 0.026), and significant reductions in daily assessments of pain (P < or = 0.040), itching (P < or = 0.032), burning (P < or = 0.028), and tenderness (P < or = 0.026) as moderate or severe. These effects were reinforced by the results of the daily self-assessment of lesion attributes, with significantly fewer severe/extreme assessments of lesion size (P < or = 0.003), noticeability (P < or = 0.003), amount of scab/crust (P < or = 0.003), raised/ swollen area (P < or = 0.040), soreness/tenderness (P < or = 0.043), and overall severity (P < or = 0.001) throughout the study period.. Penciclovir cream has demonstrated efficacy for a broad range of clinically important outcomes. Significant effects on lesion area, lesion symptoms, and other lesion attributes extend the clinical efficacy of penciclovir cream beyond lesion healing.

Topics: Acyclovir; Adolescent; Adult; Aged; Aged, 80 and over; Antiviral Agents; Double-Blind Method; Female; Guanine; Herpes Labialis; Humans; Male; Middle Aged; Ointments; Sunlight

Genital herpes simplex virus (HSV) infection, a sexually transmitted disease (STD), is the commonest cause of ulcerative genital infections among the young and adult population. The significant association of genital ulceration and transmission of human immunodeficiency virus (HIV) has been shown in many studies. To explore the potential efficacy of topical treatment of genital herpes with penciclovir cream, a randomized, double-blind, multicentre, acyclovir-controlled Phase II clinical trial of penciclovir 1% cream 5 times daily up to 7 days for suppression of genital herpes was conducted in China. A total of 205 patients aged 20-59 years (mean age 36.0+/-8.8 years for acyclovir and 34.8+/-8.4 years for penciclovir) with a clinical diagnosis of genital herpes were randomly allocated to one of the 2 parallel treatment groups and used for analysis. Clinical assessment were made before treatment and followed up at every visit during the study. Our results show that there was an encouraging improvement simultaneously in the 2 groups although no significant differences in clinical efficacy with respect to clinical cure rate, and times to healing, resolution of all symptoms, absence of blisters, cessation of new blisters, crusting, and loss of crust between penciclovir and acyclovir groups in terms of primary, non-primary and total patients were found. However a significantly shorter time to crusting was found in primary penciclovir group when compared with primary acyclovir group. Adverse experience was generally infrequent and mild, and was comparable in the 2 treatment groups. Based on these preliminary clinical findings, further evaluation of penciclovir 3% cream for topical treatment of genital herpes is planned.

Topics: Acyclovir; Administration, Topical; Adult; Antiviral Agents; China; Double-Blind Method; Female; Follow-Up Studies; Guanine; Herpes Genitalis; Humans; Male; Middle Aged; Proportional Hazards Models; Recurrence; Time Factors; Treatment Outcome

The efficacy and safety of penciclovir (PCV) for the treatment of herpes simplex virus (HSV) infections in immunocompromised (IC) patients were studied in a double-blind, acyclovir (ACV)-controlled, multicenter study. A total of 342 patients with mucocutaneous HSV infections received 5 mg of PCV per kg every 12 or 8 h (q12h or q8h) or 5 mg of ACV per kg q8h, beginning within 72 h of lesion onset and continuing for up to 7 days. The mean age of the patients was 49 years; 94% were white and 52% were female. The main reasons for their IC states were hematologic disorder (63%) and transplant plus hematologic disorder (16%). Clinical and virological assessments were performed daily during the 7-day treatment and then every other day until lesion healing. The primary efficacy parameter addressed new lesion formation. Secondary end points focused on viral shedding, healing, and pain. Approximately 20% of patients in each treatment group developed new lesions during therapy; thus, equivalence with ACV (defined prospectively) was demonstrated for both q12h and q8h PCV regimens. For all three treatment groups, the median time to the cessation of viral shedding was 4 days and the median time to complete healing was 8 days; there were no statistically significant differences in the rates of complete healing or the cessation of viral shedding when the results for PCV q12h and q8h were compared with those for ACV q8h. In addition, there was no statistically significant difference between PCV q12h or q8h, compared with ACV q8h, for the resolution of pain. PCV was well tolerated, with an adverse event profile comparable to that of ACV. In conclusion, PCV q12h is a well-tolerated and effective therapy for mucocutaneous HSV infection in IC patients and offers a reduced frequency of dosing compared with ACV q8h.

Topics: Acyclovir; Adolescent; Adult; Aged; Aged, 80 and over; Antiviral Agents; Double-Blind Method; Female; Guanine; Herpes Simplex; Humans; Immunocompromised Host; Infusions, Intravenous; Male; Middle Aged; Simplexvirus; Treatment Outcome

Penciclovir is a drug active against herpes simplex viruses located in the epidermis basal layer. The aim of this study was to compare the suction blister technique and microdialysis as methods to measure the penciclovir concentration in the skin after a single dose (250 mg) of its prodrug, famciclovir. Suction blister fluid, microdialysates and plasma were sampled from 11 healthy volunteers for 5 h after famciclovir administration. Both the suction blister technique and microdialysis showed that penciclovir reaches the skin in concentrations sufficient to inhibit herpes virus replication. The maximum concentration in both suction blister fluid and in microdialysate was observed later than in plasma. The microdialysis concentration was decreased by cooling of the skin surface and by adrenaline-mediated vasoconstriction. The microdialysis recovery of penciclovir was studied with respect to the flow-rate of perfusion medium through the microdialysis probe. Microdialysis and the suction blister technique can be used to study the time-concentration profile of penciclovir in the skin and microdialysis allows a continuous sampling of the drug for a prolonged time after administration.

Topics: 2-Aminopurine; Acyclovir; Administration, Oral; Adult; Antiviral Agents; Blister; Dialysis Solutions; Epinephrine; Famciclovir; Female; Guanine; Humans; Male; Microdialysis; Prodrugs; Skin; Temperature; Time Factors; Tissue Distribution; Vasoconstrictor Agents

To evaluate the efficacy and safety of oral famciclovir in the suppression of genital herpes.. In this randomized, double-blind, placebo-controlled trial that was performed at 11 university and 9 private ambulatory care referral centers, 375 women who were 18 years of age or older and had a history of 6 or more episodes of genital herpes during 12 of the last 24 months in the absence of suppressive therapy were treated for 4 months with oral famciclovir, 125 mg once daily or twice daily, 250 mg once daily or twice daily, 500 mg once daily, or placebo. The primary outcome measures included the time to first clinically and virologically confirmed recurrences, and safety as measured by clinical laboratory tests and adverse experiences.. The median time to first recurrence was 82 days in the placebo group, 114 days in those receiving famciclovir, 125 mg once daily, and more than 120 days in the other treatment groups. When compared with placebo recipients, the time to the first clinical recurrence was significantly prolonged in subjects who received famciclovir, 125 mg twice daily (hazard ratio, 1.8; 95% confidence interval, 1.0-3.0; P = .03), and in those who received famciclovir, 250 mg twice daily (hazard ratio, 3.6; 95% confidence interval, 1.9-6.9; P < .001). Treatment was well tolerated, and there was no evidence of emergence of resistance during or after suppressive famciclovir therapy.. Oral famciclovir, 250 mg, given twice daily for 4 months is an effective, well-tolerated treatment for the suppression of genital herpes in women with frequent recurrences, but single daily doses produced less complete suppression of genital herpes.

Topics: 2-Aminopurine; Acyclovir; Administration, Oral; Adult; Antigen-Antibody Complex; Antiviral Agents; Double-Blind Method; Famciclovir; Female; Guanine; Herpes Genitalis; Humans; In Vitro Techniques; Microbial Sensitivity Tests; Recurrence; Simplexvirus; Treatment Outcome

To compare the safety and efficacy of topical 1% penciclovir cream with vehicle control cream (placebo) for the treatment of a recurrent episode of herpes simplex labialis (cold sores) in immunocompetent patients.. Randomized, double-blind, placebo-controlled, patient-initiated, 2-armed, parallel clinical trial. Patients were prospectively dispensed study medication, and treatment was self-initiated by the patient within 1 hour of the first sign or symptom of a recurrence.. A total of 31 ambulatory clinics in the United States in a variety of settings, including private practices, public health facilities, and universities.. Otherwise healthy individuals with a history of frequent episodes of herpes simplex labialis. A total of 2209 patients were enrolled and given study medication, and 1573 initiated treatment for a recurrence.. Topical 1% penciclovir cream or vehicle control cream. Subjects applied treatment every 2 hours while awake for 4 consecutive days.. Lesion healing was the primary efficacy variable. Secondary end points included time to loss of lesion pain and time to cessation of viral shedding.. Healing of classical lesions (vesicles, ulcers, and/or crusts) was 0.7 day faster for penciclovir-treated patients compared with those who received vehicle control cream (median, 4.8 days vs 5.5 days; hazard ratio [HR], 1.33; 95% confidence interval [CI], 1.18-1.49; P<.001). Pain (median, 3.5 days vs 4.1 days; HR, 1.22; 95% CI, 1.09-1.36; P<.001) and lesion virus shedding (median, 3 days vs 3 days; HR, 1.35; 95% CI, 1.10-1.64; P=.003) also resolved more quickly for penciclovir-treated patients compared with patients who applied the vehicle control. The efficacy of penciclovir cream was apparent when therapy was initiated early (prodrome or erythema lesion stage) and when initiated late (papule or vesicle stage). The incidence of adverse events was comparable between penciclovir and placebo groups.. Penciclovir cream is the first treatment to clearly demonstrate an impact on the course of recurrent herpes labialis in immunocompetent patients. Efficacy was seen in all clinical and laboratory measures of the disease (lesion healing, pain resolution, and cessation of viral shedding). Faster healing and pain resolution occurred both among patients who first applied penciclovir cream in the prodrome and erythema stages and among those who started treatment in the papule and vesicle lesion stages.

Topics: Acyclovir; Administration, Topical; Adult; Aged; Antiviral Agents; Double-Blind Method; Female; Guanine; Herpes Labialis; Humans; Immunocompetence; Male; Middle Aged; Ointments; Pain; Proportional Hazards Models; Recurrence; Virus Shedding; Wound Healing

Topics: Acyclovir; Administration, Topical; Antiviral Agents; Costs and Cost Analysis; Guanine; Herpes Labialis; Humans

Topics: Acyclovir; Antiviral Agents; Female; Guanine; Herpes Labialis; Humans; Male; Ointments; Recurrence; Reproducibility of Results; Treatment Outcome

Twenty healthy male volunteers received single oral doses of famciclovir (125-750 mg), in a randomized, single-blind, crossover study. Plasma and urine concentrations of penciclovir and its 6-deoxy precursor, BRL 42359, were determined and penciclovir plasma concentration-time data submitted to model-independent pharmacokinetic analysis. Peak plasma concentrations of penciclovir were obtained at median times of 0.5-0.75 h after dosing. The areas under the concentration versus time curves (AUC) and the peak penciclovir concentration (Cmax) increased linearly with dose of famciclovir. Time to Cmax, elimination half-life, urinary recovery and renal clearance of penciclovir did not change with increasing dose. Famciclovir was excreted via the kidneys as penciclovir (60%) and BRL 42359 (5%), respectively. Famciclovir was well tolerated by all subjects with a low incidence of adverse effects. In conclusion, penciclovir thus displays linear pharmacokinetics in the anticipated therapeutic dose range of famciclovir.

Topics: 2-Aminopurine; Acyclovir; Administration, Oral; Adult; Antiviral Agents; Chromatography, High Pressure Liquid; Famciclovir; Guanine; Half-Life; Humans; Male; Middle Aged; Prodrugs; Single-Blind Method; Spectrophotometry, Ultraviolet

A novel MS-based analytical method for simultaneous analysis of the antiviral drugs acyclovir, its metabolite 9-carboxymethoxymethylguanine, ganciclovir, and penciclovir in human serum is described. These antiviral drugs are active against herpes virus infections. Acyclovir and penciclovir are regarded as safe and effective medicines with mild side effects such as headache and gastrointestinal discomfort, and ganciclovir is regarded as more toxic and is known to cause, for example, bone marrow suppression. Acyclovir's main metabolite 9-carboxymethoxymethylguanine is a presumptive neurotoxin and should be monitored in patients with impaired renal function or in cases with neurotoxic symptoms. A sample was prepared using protein precipitation with 1% formic acid in methanol containing isotopically labeled internal standard. Chromatographic separation on a biphenyl column and mass spectrometric detection were performed in multiple reaction monitoring (MRM) mode on a Xevo TQ-S micro with ESI in positive ion mode, within 3 min. Inter-day assay accuracies for the quality controls varied between 95 and 104% and intra-day assay between 93 and 105%. Inter-day and intra-day assay imprecision for the quality controls ranged between 1.4 and 4.2% and 1.7 and 6.5% respectively. The lower limit of quantification for all four substances was 0.156 μmol/L. It is an accurate and reproducible method for therapeutic drug monitoring.

Topics: Acyclovir; Chromatography, Liquid; Ganciclovir; Guanine; Humans; Reproducibility of Results; Tandem Mass Spectrometry

Acyclovir (ACV) and penciclovir and their prodrugs are recommended for therapy or prophylaxis of Herpes simplex virus 1 (HSV-1) infections. Their administration, however, can lead to the emergence of resistant strains with altered viral thymidine kinase (TK) function, especially in immunocompromised patients. Furthermore, amino acid (aa) changes of the viral deoxyribonucleic acid polymerase (POL) may contribute to resistance to the aforementioned nucleoside analogues. Given this, treatment with foscarnet (FOS) or cidofovir (CDV) may represent an important alternative. Both drugs directly affect POL activity. Several aa changes of POL, such as L49I, E70K, L359I, E421V, P829S, T1121M, and M1226I, have been observed in ACV-resistant clinical strains which also carried relevant aa changes in their TK. Their contribution to ACV, FOS, and CDV resistance is not fully understood. In this study, these seven aa changes with unknown significance for ACV, FOS and CDV resistance were introduced separately into the POL of a recombinant HSV-1 strain rHSV-1(17+)Lox, equipped with or without information for expression of green fluorescent protein (GFP). The GFP-expressing variants were tested for susceptibility to ACV, FOS and CDV. An rHSV-1(17+)Lox GFP strain with the S724N change conferring resistance to ACV and FOS was generated and included as a control. Only the S724N change was confirmed to induce ACV and FOS resistance, whereas the other changes did not contribute to resistance. The underlying nucleotide substitutions of the POL gene should be therefore considered as natural polymorphism. These data will improve sequence-based prediction of antiviral susceptibility.

Topics: Acyclovir; Animals; Antiviral Agents; Chlorocebus aethiops; Cidofovir; DNA-Directed DNA Polymerase; Drug Resistance, Viral; Foscarnet; Guanine; Herpes Simplex; Herpesvirus 1, Human; Humans; Immunocompromised Host; Microbial Sensitivity Tests; Thymidine Kinase; Vero Cells

The Chinese Herbal Prescription JieZe-1(JZ-1), added and subtracted from Yihuang Decoction, a famous formula in the 12th year of Kangxi in Qing Dynasty, has a clear effect on Genital Herpes (GH) and no obvious adverse reactions occur clinically. JZ-1 also has preventive and therapeutic effects on Trichomonas vaginitis, Candida albicans vaginitis and GH in vitro and in vivo experiments.. The effect and mechanism of JZ-1 on anti-herpes simplex virus type 2(HSV-2) in vitro focusing on adhesion and penetration stages were investigated.. A model of HSV-2 infection of VK2/E6E7 was developed. In order to explore JZ-1's anti-HSV-2 effect in vitro, cell morphology, ultrastructural pathology, cell viability and expression of viral glycoprotein D (gD) were assessed at 6 h, 12 h, 18 h, and 24 h of JZ-1 treatment. Then we measured the exact time required for adhesion and penetration of HSV-2 into VK2/E6E7 among a series of times at room temperature and under temperature control techniques. We treated VK2/E6E7 with JZ-1, penciclovir, or berberine and explored the mechanism of JZ-1 in blocking HSV-2 adhesion and penetration of host cells by assessing the cell ultrastructural pathology, viability, viral proteins gB, gD, VP16, ICP5, and ICP4 and host cell proteins HVEM, Nectin-1, and Nectin-2.. HSV-2 can fully adhere and penetrate into VK/E6E7 within 5 mins at room temperature while it takes 60mins under temperature control techniques. JZ-1 and penciclovir showed significant anti-HSV-2 effects, with improved host cell morphologies and increased host cell viabilities observed after treatment for 24 h. The anti-HSV-2 effect of JZ-1 can be detected after treatment for 6 h while that of penciclovir was not obvious until treatment for 12 h. JZ-1 showed distinct effect on HSV-2 adhesion and penetration stages by significantly reducing the expression of viral proteins gB, gD, VP16, ICP5, and ICP4, improving cell morphology and increasing cell viability. However, these effects were not exerted via downregulated expression of membrane fusion-related proteins such as HVEM, Nectin-1, or Nectin-2. The specific anti-HSV-2 mechanism of JZ-1 need to be further explored.. The anti-HSV-2 effect of JZ-1 was superior to that of penciclovir and berberine in vitro, and was mainly mediated by enhancing host cell defense and blocking adhesion and penetration of HSV-2.

Topics: Acyclovir; Antiviral Agents; Berberine; Cell Line; Drugs, Chinese Herbal; Epithelial Cells; Female; Guanine; Herpes Genitalis; Herpesvirus 2, Human; Humans; Vagina; Virus Attachment; Virus Internalization

АBSTRACTEsters of the antiherpetic drugs ganciclovir, penciclovir with the bile acids (cholic, chenodeoxycholic and deoxycholic) and amino acid esters of acyclovir were generated and evaluated for their in vitro antiviral activity against herpes simplex viruses type 1 and type 2 (HSV-1, HSV-2). The antiviral assays demonstrated that modified analogs of ACV and PCV are less active compared to the initial substances against HSV-1and HSV-2. CC50 for ganciclovir-deoxycholate corresponded to the CC50 of the other analogs and its activity is lower than ganciclovir. Obtained results show that tested modification do not improve bioavailability of nucleoside analogs in cells.

Topics: Acyclovir; Animals; Antiviral Agents; Cattle; Cell Line; Cell Survival; Dose-Response Relationship, Drug; Ganciclovir; Guanine; Herpesvirus 1, Human; Herpesvirus 2, Human; Microbial Sensitivity Tests; Molecular Structure; Structure-Activity Relationship

Recently, a pathogen has been identified as a novel coronavirus (SARS-CoV-2) and found to trigger novel pneumonia (COVID-19) in human beings and some other mammals. The uncontrolled release of cytokines is seen from the primary stages of symptoms to last acute respiratory distress syndrome (ARDS). Thus, it is necessary to find out safe and effective drugs against this deadly coronavirus as soon as possible. Here, we downloaded the three-dimensional model of NSP10/NSP16 methyltransferase (PDB-ID: 6w6l) and main protease (PDB-ID: 6lu7) of COVID-19. Using these molecular models, we performed virtual screening with our anti-viral, inti-infectious, and anti-protease compounds, which are attractive therapeutics to prevent infection of the COVID-19. We found that top screened compound binds with protein molecules with good dock score with the help of hydrophobic interactions and hydrogen bonding. We observed that protease complexed with Cyclocytidine hydrochloride (anti-viral and anti-cancer), Trifluridine (anti-viral), Adonitol, and Meropenem (anti-bacterial), and Penciclovir (anti-viral) bound with a good docking score ranging from -6.8 to -5.1 (Kcal/mol). Further, NSP10/NSP16 methyltransferase complexed with Telbivudine, Oxytetracycline dihydrate (anti-viral), Methylgallate (anti-malarial), 2-deoxyglucose and Daphnetin (anti-cancer) from the docking score of -7.0 to -5.7 (Kcal/mol). In conclusion, the selected compounds may be used as a novel therapeutic agent to combat this deadly pandemic disease, SARS-CoV-2 infection, but needs further experimental research.HighlightsNSP10/NSP16 methyltransferase and main protease complex of SARS CoV-2 bind with selected drugs.NSP10/NSP16 methyltransferase and protease interacted with drugs by hydrophobic interactions.Compounds show good DG binging free energy with protein complexes.Ligands were found to follow the Lipinski rule of five.

Topics: Acyclovir; Ancitabine; Antiviral Agents; Betacoronavirus; Coronavirus Infections; COVID-19; Drug Evaluation, Preclinical; Guanine; Humans; Meropenem; Methyltransferases; Models, Molecular; Molecular Docking Simulation; Pandemics; Pneumonia, Viral; Protein Conformation; Ribitol; SARS-CoV-2; Trifluridine; User-Computer Interface; Viral Nonstructural Proteins; Viral Regulatory and Accessory Proteins

A series of tricyclic penciclovir (PCV) and hydroxybutylguanine (HBG) derivatives have been prepared with enhanced lipophilicity following an efficient synthetic route. All the novel tricyclic derivatives were evaluated for inhibitory activity against herpes simplex virus 1 and 2 (HSV-1, HSV-2) and thymidine kinase deficient (ACV resistant) HSV-1. The tricyclic HBG derivatives were devoid of inhibitory activity however several of the tricyclic PCV derivatives showed promising antiviral activity, in particular 9g (R = 4-MeO-C

Topics: Acyclovir; Antiviral Agents; Guanine; Herpes Genitalis; Herpes Simplex; Herpesvirus 1, Human; Herpesvirus 2, Human; Humans; Models, Molecular

1. Penciclovir, ganciclovir, creatinine, para-aminohippuric acid (PAH), ketoprofen, estrone 3-O-sulfate (E3S), dehydroepiandrosterone 3-O-sulfate (DHEAS) and cyclic guanosine monophosphate (cGMP) were screened as substrates of human liver organic anion transporters OAT2 and OAT7. 2. For OAT7, high uptake ratios (versus mock transfected HEK293 cells) of 29.6 and 15.3 were obtained with E3S and DHEAS. Less robust uptake ratios (≤3.6) were evident with the other substrates. OAT2 (transcript variant 1, OAT2-tv1) presented high uptake ratios of 30, 13, ∼35, ∼25, 8.5 and 9 with cGMP, PAH, penciclovir, ganciclovir, creatinine and E3S, respectively. No uptake was observed with DHEAS. 3. Although not a substrate of either transporter, ketoprofen did inhibit transfected OAT2-tv1 (IC

Topics: Acyclovir; Adult; Estrone; Female; Guanine; HEK293 Cells; Hepatocytes; Humans; Ketoprofen; Organic Anion Transporters, Sodium-Independent; Peptides; Proteomics; RNA, Messenger; Substrate Specificity; Transfection

Therapy or prophylaxis of herpes simplex virus type 2 (HSV-2) infections with the nucleoside analog aciclovir (ACV) can lead to the emergence of drug-resistant HSV-2 strains, particularly in immunocompromised patients. In this context, multiple amino acid (aa) changes can accumulate in the ACV-converting viral thymidine kinase (TK) which hampers sequence-based diagnostics significantly. In this study, the so far unknown or still doubted relevance of several individual aa changes for drug resistance in HSV-2 was clarified. For this purpose, ten recombinant fluorescent HSV-2 strains differing in the respective aa within their TK were constructed using the bacterial artificial chromosome (BAC) pHSV2(MS)Lox. Similar TK expression levels and similar replication behavior patterns were demonstrated for the mutants as compared to the unmodified BAC-derived HSV-2 strain. Subsequently, the resulting strains were tested for their susceptibility to ACV as well as penciclovir (PCV) in parallel to a modified cytopathic effect (CPE) inhibition assay and by determining the relative fluorescence intensity (quantified using units, RFU) as a measure for the viral replication capacity. While aa changes Y53N and R221H conferred ACV resistance with cross-resistance to PCV, the aa changes G25A, G39E, T131M, Y133F, G150D, A157T, R248W, and L342W maintained a susceptible phenotype against both antivirals. The CPE inhibition assay and the measurement of relative fluorescence intensity yielded comparable results for the phenotypic testing of recombinant viruses. The latter test showed some technical advantages. In conclusion, the significance of single aa changes in HSV-2 TK on ACV/PCV resistance was clarified by the construction and phenotypic testing of recombinant viral strains. This was facilitated by the fluorescence based method.

Topics: Acyclovir; Antiviral Agents; Drug Resistance, Viral; Guanine; Herpes Simplex; Herpesvirus 2, Human; Humans; Mutation; Thymidine Kinase; Viral Proteins

Equid herpesvirus 1 (EHV-1) is a pathogen of high economic importance in equine breeding operations around the world. EHV-1 infection causes respiratory, neurologic and reproductive disease. The absence of an efficient therapy has caught the attention of the scientific community and the therapeutic activities of natural products with its antivirals effects might be effective for the disease's treatment. Herein it was evaluated the prophylactic and therapeutic potential of quercetin and ethanolic extracts of Bacharis dracunculifolia formulations compared to Penciclovir® in an in vivo EHV-1 infection model. Six to seven-week-old female C57BL/6 mice were randomly organized into fifteen groups with six animals each. Ex-1 represents the treatment post-challenge groups to assess morbidity, mortality and weight variation. Ex-2 represents the animals that received treatment for 5 days post-challenge for lesion evaluation. In Ex-3 animals were treated prior to viral challenge to assess morbidity, mortality and weight variation. All mice in the treatment groups were challenged by intranasal inoculation of 3.0 × 10

Topics: Acyclovir; Administration, Intranasal; Animals; Antiviral Agents; Asteraceae; Disease Models, Animal; Female; Guanine; Herpesviridae Infections; Herpesvirus 1, Equid; Horses; Mice; Mice, Inbred C57BL; Phytotherapy; Plant Extracts; Quercetin; Random Allocation

Acyclovir and penciclovir, 2 antiviral drugs, are increasingly detected in aquatic environments. The present study explores the natural photochemical transformation mechanisms and fate of these drugs, examining direct and indirect photochemical transformation under simulated sunlight irradiation. The 2 antiviral drugs are photostable under certain conditions but significantly degrade in the presence of chromophoric dissolved organic matter (DOM). The degradation rate associated with the drugs' indirect photochemical transformation scaled with chromophoric DOM concentration. Quenchers and sensitizers were used to identify indirect photochemical transformation mechanism. Results suggested that both pharmaceuticals could be transformed by reacting with (1)O2, (•)OH, and excited chromophoric DOM. The (1)O2 played an important role in indirect photochemical transformation. Furthermore, the reaction kinetics between their substructural molecules, guanine, isocytosine, and imidazole, with different reactive oxygen species were evaluated to determine which substrate functionalities were most susceptible to singlet oxygenation. Imidazole was identified as the reaction site for (1)O2, and preliminary (1)O2 oxidation mechanisms were further evaluated based on liquid chromatographic-tandem mass spectrometric results. Finally, aquatic ecotoxicity assessment of phototransformed solutions revealed that the degradation of acyclovir and penciclovir may not ultimately diminish environmental risk because of either formation of more toxic intermediates than parent pharmaceuticals or some synergistic effects existing between the intermediates.

Topics: Acyclovir; Animals; Antiviral Agents; Chromatography, High Pressure Liquid; Daphnia; Guanine; Kinetics; Microalgae; Oxidation-Reduction; Photobacterium; Risk Assessment; Singlet Oxygen; Sunlight; Tandem Mass Spectrometry

Some nucleoside analogues are used to treat herpes simplex and other viral infections. They are known to impair spermatogenesis, but published data are scarce. We studied the effects of four nucleosides on SerW3 cells, a rat Sertoli cell line. Cells were cultured for 3 days in DMEM supplemented with four different concentrations of each drug. Aciclovir and ganciclovir were added at concentrations of 0.3, 1, 3 and 10 mg/l medium; penciclovir and its prodrug famciclovir were used at higher concentrations (3, 10, 30, 100 mg/l medium). After a culture period of 3 days, we analysed the expression of connexin43, N-cadherin and the cytoskeleton protein vimentin by Western blot. Aciclovir caused a clear-cut effect at the highest concentration tested (10 mg/l), which is less than the peak plasma concentration achieved in patients during intravenous therapy with the drug. Connexin43, vimentin and N-cadherin content decreased to 49.8 ± 17, 44.0 ± 4 and 75.4 ± 1.5 % of the control values, respectively (n = 3; mean ± SD). Similar effects were observed with the prodrug ganciclovir (43.2 ± 10.8; 54.1 ± 11.9; 84.4 ± 10.8 % of controls). Penciclovir caused less pronounced effects at 10 mg/l medium (82.1 ± 20.6; 90.0 ± 12.0; 76.5 ± 17.7 % of controls). Only a slight effect was observed with famciclovir. Even at a 10-fold concentration (100 mg/l), just moderate changes were induced. In summary, we observed clear-cut effects with aciclovir and ganciclovir on Sertoli cells in vitro at therapeutically relevant concentrations and identified connexin43 as the most sensitive marker.

Topics: 2-Aminopurine; Acyclovir; Animals; Antiviral Agents; Biomarkers; Blotting, Western; Cadherins; Cell Culture Techniques; Cell Line; Connexin 43; Dose-Response Relationship, Drug; Famciclovir; Ganciclovir; Guanine; Male; Microscopy, Fluorescence; Nerve Tissue Proteins; Rats; Sertoli Cells; Vimentin

To assess in vitro the antiviral efficacy against feline herpesvirus (FHV-1) and cytotoxicity for cultured feline cells of famciclovir and its metabolites, BRL 42359 and penciclovir. To investigate the effect of timing of penciclovir application on in vitro antiviral activity.. Plaque reduction assays were used to estimate antiviral efficacy of all compounds and the effect of penciclovir exposure before or after exposure to a FHV-1 field isolate. Cytotoxicity was evaluated by assessing cell morphology and viable cell number for 72 h following exposure to each compound.. The penciclovir concentration that inhibited FHV-1-induced plaque formation by 50% (IC50 ) was 0.86 μg/mL (3.4 μm). Famciclovir and BRL 42359 had no antiviral effect against FHV-1 at any concentration assessed. Antiviral activity was significantly enhanced when cells were exposed to 4 μm penciclovir (approximate IC50 ) for 1 h but not for 24 h before viral adsorption. Delaying exposure of cells to penciclovir for 1, 2, or 4 h after viral adsorption significantly enhanced antiviral activity. Relative to untreated control wells, >88% of cells remained viable when exposed to famciclovir (100 μm), BRL 42359 (1.06 mm), or penciclovir (40 μm) for 72 h. No morphologic evidence of cytotoxicity was noted.. Penciclovir demonstrates potent antiviral activity against FHV-1 and may be effective at lower tissue, tear, and plasma concentrations than previously targeted. The duration of in vitro antiviral effect of penciclovir suggests that frequent famciclovir administration may be necessary in vivo. Famciclovir and BRL 42359 showed no signs of in vitro cytotoxicity.

Topics: 2-Aminopurine; Acyclovir; Animals; Antiviral Agents; Cats; Cell Line; Dose-Response Relationship, Drug; Famciclovir; Guanine; Herpesviridae; Inhibitory Concentration 50; Viral Plaque Assay

Herpesviruses are ubiquitous pathogens that infect and cause recurrent disease in multiple animal species. Feline herpesvirus-1 (FHV-1), a member of the alphaherpesvirus family, causes respiratory illness and conjunctivitis, and approximately 80% of domestic cats are latently infected. Oral administration of famciclovir or topical application of cidofovir has been shown in masked, placebo-controlled prospective trials to reduce clinical signs and viral shedding in experimentally inoculated cats. However, to the authors' knowledge, other drugs have not been similarly assessed or were not safe or effective. Likewise, to our knowledge, no drugs have been assessed in a placebo-controlled manner in cats with recrudescent herpetic disease. Controlled-release devices would permit long-term administration of these drugs and enhance compliance.. We therefore engineered implantable cylindrical devices made from silicone (MED-4750) impregnated with penciclovir, for long-term, steady-state delivery of this drug.. Our data show that these devices release penciclovir with a burst of drug delivery until the tenth day of release, then at an average rate of 5.063 ± 1.704 μg per day through the next 50 days with near zero-order kinetics (in comparison to MED-4750-acyclovir devices, which show the same burst kinetics and average 2.236 ± 0.625 μg/day thereafter). Furthermore, these devices suppress primary infection of FHV-1 in a cell culture system.. The clinical deployment of these silicone-penciclovir devices may allow long-term treatment of FHV-1 infection with a single intervention that could last the life of the host cat.

Topics: Acyclovir; Animals; Antiviral Agents; Cats; Cells, Cultured; Drug Delivery Systems; Guanine; Polymers; Silicones; Varicellovirus

The role of mutations in the thymidine kinase (TK, UL23) and DNA polymerase (pol, UL30) genes of herpes simplex virus (HSV) for development of different resistance phenotypes has to be exactly determined before genotypic resistance testing can be implemented in patient's care. Furthermore, the occurrence of cross-resistance is of utmost clinical importance. In this study, clinical HSV-1 isolates obtained between 2004 and 2011 from 26 patients after stem cell transplantation were examined in parallel by phenotypic and genotypic resistance testing. Thirteen isolates, which were phenotypically cross-resistant to acyclovir (ACV), penciclovir (PCV) and brivudin (BVDU), exhibited consistently frameshift or non-synonymous mutations in the TK gene known to confer resistance. One of these mutations (insertion of C at the nucleotide positions 1061-1065) has not been described before. Seven strains, phenotypically resistant to ACV and PCV and, except one each, sensitive to BVDU and resistant to foscarnet (FOS), carried uniformly resistance-related substitutions in the DNA pol gene. Finally, 3 isolates, resistant to ACV, PCV and 2 out of these also resistant to BVDU, had known but also unclear substitutions in the TK and DNA pol genes, and 3 isolates were completely sensitive. In conclusion, clinical ACV-resistant HSV-1 isolates, carrying resistance-associated mutations in the TK gene, can be regarded as cross-resistant to other nucleoside analogs such as BVDU. In contrast, clinical FOS-resistant HSV-1 strains which are cross-resistant to ACV may be sensitive to BVDU. This has to be considered for drug changes in antiviral treatment in case of ACV resistance.

Topics: Acyclovir; Adolescent; Adult; Aged; Antiviral Agents; Bromodeoxyuridine; Child; DNA-Directed DNA Polymerase; DNA, Viral; Drug Resistance, Viral; Exodeoxyribonucleases; Female; Frameshift Mutation; Guanine; Herpes Simplex; Herpesvirus 1, Human; Humans; Male; Microbial Sensitivity Tests; Middle Aged; Mutagenesis, Insertional; Mutation, Missense; Point Mutation; Polymorphism, Single Nucleotide; Sequence Analysis, DNA; Thymidine Kinase; Viral Proteins; Young Adult

Varicella zoster virus (VZV), a member of the human herpesvirus family, affects peripheral or cranial nerves and can reactivate years after the primary infection. Thymidine kinase (TK) is essential for VZV replication, and its active site is highly conserved in the herpesvirus family. A number of small-molecule inhibitors have already been successfully developed that target the TK of herpes simplex virus type 1 (HSV-1), which is one of the most prevalent sexually transmitted infections worldwide. In the present study, we attempted to test the sensitivities of HSV-1 TK inhibitors to their noncognate VZV TK by integrating in silico modeling and an in vitro assay. We tested nine representative HSV-1 TK inhibitors, including three FDA-approved drugs and six compounds that are under clinical development. The structures of the complexes of these inhibitor ligands with HSV-1 TK and noncognate VZV TK had been solved previously by X-ray crystallography or were modeled in the present work using a template-based approach. Subsequently, a rigorous quantum mechanics/molecular mechanics (QM/MM) nonbonded analysis that accounted for the Poisson-Boltzmann/surface area (PB/SA) solvent effect was employed to refine the complex structures and, on this basis, to evaluate the binding potencies of these complexes. As might be expected, the QM/MM-PB/SA-derived free energy was shown to be highly correlated with the HSV-1 TK inhibitory activities of the nine inhibitors. Further, it was found that the HSV-1 TK inhibitors exhibit strong binding affinities for their noncognate VZV TK, although they are still more selective for HSV-1 TK than for VZV TK. In order to test the theoretical results obtained from the computational analysis, we performed an in vitro kinase assay to determine the inhibitory potencies of three commercially available antiviral agents, namely penciclovir, ganciclovir, and aciclovir, against their noncognate target VZV TK, resulting in IC50 values of 86, 127, and 150 μM respectively, which are modestly weaker than the corresponding values obtained for HSV-1 TK. In addition, visual structure examination and virtual mutation/deletion analysis suggested that the residue Arg222 is present at the active site of HSV-1 TK but not at the active site of VZV TK, which is the reason for the difference in inhibitor selectivity between HSV-1 TK and VZV TK.

Topics: Acyclovir; Amino Acid Sequence; Antiviral Agents; Binding Sites; Computer-Aided Design; Drug Design; Enzyme Inhibitors; Ganciclovir; Guanine; Herpesvirus 1, Human; Herpesvirus 3, Human; Humans; Ligands; Molecular Docking Simulation; Molecular Sequence Data; Molecular Structure; Neuralgia, Postherpetic; Protein Binding; Protein Conformation; Structure-Activity Relationship; Thymidine Kinase; Viral Proteins

The susceptibilities of gammaherpesviruses, including Epstein-Barr virus (EBV), Kaposi's sarcoma-associated herpesvirus (KSHV), and animal rhadinoviruses, to various nucleoside analogs was investigated in this work. Besides examining the antiviral activities and modes of action of antivirals currently marketed for the treatment of alpha- and/or betaherpesvirus infections (including acyclovir, ganciclovir, penciclovir, foscarnet, and brivudin), we also investigated the structure-activity relationship of various 5-substituted uridine and cytidine molecules. The antiviral efficacy of nucleoside derivatives bearing substitutions at the 5 position was decreased if the bromovinyl was replaced by chlorovinyl. 1-β-D-Arabinofuranosyl-(E)-5-(2-bromovinyl)uracil (BVaraU), a nucleoside with an arabinose configuration of the sugar ring, exhibited no inhibitory effect against rhadinoviruses but was active against EBV. On the other hand, the fluoroarabinose cytidine analog 2'-fluoro-5-iodo-aracytosine (FIAC) showed high selectivity indices against gammaherpesviruses that were comparable to those of brivudin. Additionally, we selected brivudin- and acyclovir-resistant rhadinoviruses in vitro and characterized them by phenotypic and genotypic (i.e., sequencing of the viral thymidine kinase, protein kinase, and DNA polymerase) analysis. Here, we reveal key amino acids in these enzymes that play an important role in substrate recognition. Our data on drug susceptibility profiles of the different animal gammaherpesvirus mutants highlighted cross-resistance patterns and indicated that pyrimidine nucleoside derivatives are phosphorylated by the viral thymidine kinase and purine nucleosides are preferentially activated by the gammaherpesvirus protein kinase.

Topics: Acyclovir; Amino Acid Sequence; Animals; Antiviral Agents; Arabinofuranosyluracil; Bromodeoxyuridine; Cytarabine; DNA-Directed DNA Polymerase; Drug Resistance, Viral; Foscarnet; Ganciclovir; Guanine; Herpesvirus 4, Human; Herpesvirus 8, Human; Humans; Molecular Sequence Data; Protein Kinases; Rhadinovirus; Sequence Alignment; Structure-Activity Relationship; Thymidine Kinase; Viral Proteins

In comparison to the range of antibiotics used in medicine, the spectrum of antifungal and antiviral drugs used in primary dental care is relatively limited. In practical terms, there are only three antifungal agents and two antiviral agents that have a role. This paper will describe the clinical presentation of orofacial candidal and viral infections and the use of antimicrobial drugs in their management.

Topics: Acyclovir; Amphotericin B; Antifungal Agents; Antiviral Agents; Candidiasis, Oral; Cheilitis; Dental Care; Fluconazole; Glossitis; Guanine; Herpes Zoster; Humans; Miconazole; Mouth Diseases; Nystatin; Primary Health Care; Stomatitis, Herpetic

We developed a population model that describes the ocular penetration and pharmacokinetics of penciclovir in human aqueous humour and plasma after oral administration of famciclovir.. Fifty-three patients undergoing cataract surgery received a single oral dose of 500 mg of famciclovir prior to surgery. Concentrations of penciclovir in both plasma and aqueous humour were measured by HPLC with fluorescence detection. Concentrations in plasma and aqueous humour were fitted using a two-compartment model (NONMEM software). Inter-individual and intra-individual variabilities were quantified and the influence of demographics and physiopathological and environmental variables on penciclovir pharmacokinetics was explored.. Drug concentrations were fitted using a two-compartment, open model with first-order transfer rates between plasma and aqueous humour compartments. Among tested covariates, creatinine clearance, co-intake of angiotensin-converting enzyme inhibitors and body weight significantly influenced penciclovir pharmacokinetics. Plasma clearance was 22.8±9.1 L/h and clearance from the aqueous humour was 8.2×10(-5) L/h. AUCs were 25.4±10.2 and 6.6±1.8 μg·h/mL in plasma and aqueous humour, respectively, yielding a penetration ratio of 0.28±0.06. Simulated concentrations in the aqueous humour after administration of 500 mg of famciclovir three times daily were in the range of values required for 50% growth inhibition of non-resistant strains of the herpes zoster virus family.. Plasma and aqueous penciclovir concentrations showed significant variability that could only be partially explained by renal function, body weight and comedication. Concentrations in the aqueous humour were much lower than in plasma, suggesting that factors in the blood-aqueous humour barrier might prevent its ocular penetration or that redistribution occurs in other ocular compartments.

Topics: 2-Aminopurine; Acyclovir; Administration, Oral; Adult; Aged; Aged, 80 and over; Antiviral Agents; Aqueous Humor; Famciclovir; Female; Guanine; Humans; Male; Middle Aged; Models, Statistical; Plasma

The efficient syntheses of 5-(2-hydroxyethyl)- and 5-(3-hydroxypropyl)-substituted pyrimidine derivatives bearing 2,3-dihydroxypropyl, acyclovir-, ganciclovir- and penciclovir-like side chains are reported. A synthetic approach that included the alkylation of an N-anionic-5-substituted pyrimidine intermediate (method A) provided the target acyclonucleosides in significantly higher overall yields in comparison to those obtained by method B using sylilation reaction. The phosphorylation assays of novel compounds as potential substrates for thymidine kinase of herpes simplex virus type 1 (HSV-1 TK) showed that solely pyrimidine 5-substituted acyclonucleosides with a penciclovir-like side chain acted as a fraudulent substrates of HSV-1 TK. Moreover, the uracil derivative with penciclovir-like side chain with less bulky 2-hydroxyethyl substituent at C-5 proved to be a better substrate than the corresponding one with a 3-hydroxypropyl substituent. Therefore, this acyclonucleoside was selected as a lead compound for the development of a positron emission tomography HSV-1 TK activity imaging agent.

Topics: Acyclovir; Antiviral Agents; Cell Line; Fibroblasts; Ganciclovir; Guanine; Herpes Simplex; Herpesvirus 1, Human; Humans; Positron-Emission Tomography; Pyrimidine Nucleosides; Radiography; Thymidine Kinase

The organic anion transporters 1 and 3 (OAT1 and OAT3) and organic cation transporter 2 (OCT2) are important for renal tubular drug secretion. In contrast, evidence for OAT2 expression in the human kidney is limited, and its role in renal drug transport is unknown. Both mRNA (real-time polymerase chain reaction) and protein (Western blotting) for OAT2 were detected in renal cortex from eight donors, and interindividual variability in protein levels was 3-fold. OAT2 protein in the renal cortex was localized (by immunohistochemistry) to the basolateral domain of tubules, as were OAT1 and OAT3. The absolute abundance of OAT2 mRNA was similar to that of OAT1 mRNA and 3-fold higher than that of OCT2 mRNA but 10-fold lower than that of OAT3 mRNA. A previous observation that OAT2 transports cGMP led us to examine whether acyclovir, ganciclovir, and penciclovir are OAT2 substrates; they are guanine-containing antivirals that undergo active tubular secretion. Transport of the antivirals into human embryonic kidney cells was stimulated 10- to 20-fold by expression of OAT2, but there was little to no transport of the antivirals by OAT1, OAT3, or OCT2. The K(m) values for acyclovir, ganciclovir, and penciclovir transport were 94, 264, and 277 μM, respectively, and transport efficiencies were relatively high (6-24 μl · min(-1) · mg protein(-1)). This study provides definitive evidence for the expression of OAT2 in the human kidney and is the first to demonstrate that OAT2, compared with OAT1, OAT3, or OCT2, has a preference for antiviral drugs mainly eliminated in the urine via active secretion.

Topics: Acyclovir; Adolescent; Adult; Antiviral Agents; Biological Transport; Cells, Cultured; Cyclic GMP; Female; Ganciclovir; Guanine; HEK293 Cells; Humans; Kidney; Male; Middle Aged; Organic Anion Transporters, Sodium-Independent; Organic Cation Transport Proteins; Organic Cation Transporter 2; RNA, Messenger; Young Adult

To investigate the pharmacokinetics of penciclovir in healthy cats following oral administration of famciclovir or IV infusion of penciclovir.. 6 cats.. Cats received famciclovir (40 [n = 3] or 90 [3] mg/kg, PO, once) in a balanced crossover-design study; the alternate dose was administered after a ≥ 2-week washout period. After another washout period (≥ 4 weeks), cats received an IV infusion of penciclovir (10 mg/kg delivered over 1 hour). Plasma penciclovir concentrations were analyzed via liquid chromatography-mass spectrometry at fixed time points after drug administration.. Mean ± SD maximum plasma concentration (C(max)) of penciclovir following oral administration of 40 and 90 mg of famciclovir/kg was 1.34 ± 0.33 μg/mL and 1.28 ± 0.42 μg/mL and occurred at 2.8 ± 1.8 hours and 3.0 ± 1.1 hours, respectively; penciclovir elimination half-life was 4.2 ± 0.6 hours and 4.8 ± 1.4 hours, respectively; and penciclovir bioavailability was 12.5 ± 3.0% and 7.0 ± 1.8%, respectively. Following IV infusion of penciclovir (10 mg/kg), mean ± SD penciclovir clearance, volume of distribution, and elimination half-life were 4.3 ± 0.8 mL/min/kg, 0.6 ± 0.1 L/kg, and 1.9 ± 0.4 hours, respectively.. Penciclovir pharmacokinetics following oral administration of famciclovir were nonlinear within the dosage range studied, likely because of saturation of famciclovir metabolism. Oral administration of famciclovir at 40 or 90 mg/kg produced similar C(max) and time to C(max) values. Therefore, the lower dose may have similar antiviral efficacy to that proven for the higher dose.

Topics: 2-Aminopurine; Acyclovir; Administration, Oral; Animals; Antiviral Agents; Area Under Curve; Biological Availability; Cats; Cross-Over Studies; Famciclovir; Female; Guanine; Half-Life; Male; Prodrugs

To determine plasma pharmacokinetics of penciclovir following oral and rectal administration of famciclovir to young Asian elephants (Elephas maximus).. 6 healthy Asian elephants (5 females and 1 male), 4.5 to 9 years old and weighing 1,646 to 2,438 kg.. Famciclovir was administered orally or rectally in accordance with an incomplete crossover design. Three treatment groups, each comprising 4 elephants, received single doses of famciclovir (5 mg/kg, PO, or 5 or 15 mg/kg, rectally); there was a minimum 12-week washout period between subsequent famciclovir administrations. Serial blood samples were collected after each administration. Samples were analyzed for famciclovir and penciclovir with a validated liquid chromatography-mass spectroscopy assay.. Famciclovir was tolerated well for both routes of administration and underwent complete biotransformation to the active metabolite, penciclovir. Mean maximum plasma concentration of penciclovir was 1.3 μg/mL at 1.1 hours after oral administration of 5 mg/kg. Similar results were detected after rectal administration of 5 mg/kg. Mean maximum plasma concentration was 3.6 μg/mL at 0.66 hours after rectal administration of 15 mg/kg; this concentration was similar to results reported for humans receiving 7 mg/kg orally.. Juvenile Asian elephants are susceptible to elephant endotheliotropic herpesvirus. Although most infections are fatal, case reports indicate administration of famciclovir has been associated with survival of 3 elephants. In Asian elephants, a dose of 8 to 15 mg of famciclovir/kg given orally or rectally at least every 8 hours may result in penciclovir concentrations that are considered therapeutic in humans.

Topics: 2-Aminopurine; Acyclovir; Administration, Oral; Administration, Rectal; Animals; Antiviral Agents; Area Under Curve; Chromatography, Liquid; Cross-Over Studies; Elephants; Famciclovir; Female; Guanine; Half-Life; Male; Mass Spectrometry

A rapid, specific and sensitive liquid chromatography tandem mass spectrometry (LC-MS/MS) method was developed for the determination of penciclovir in human plasma. The method involved simple, one-step SPE procedure coupled with a C(18) , 75 × 4.mm, 3 µm column with a flow-rate of 0.5 mL/min, and acyclovir was used as the internal standard. The Quattro Micro mass spectrometry was operated under the multiple reaction-monitoring mode using the electrospray ionization technique. Using 250 µL plasma, the methods were validated over the concentration range 52.555-6626.181 ng/mL, with a lower limit of quantification of 52.55 ng/mL. The intra- and inter-day precision and accuracy values were found to be within the assay variability limits as per the FDA guidelines. The developed assay method was applied to a clinical pharmacokinetic study in human volunteers.

Topics: Acyclovir; Chromatography, Liquid; Drug Stability; Guanine; Humans; Linear Models; Male; Reproducibility of Results; Sensitivity and Specificity; Spectrometry, Mass, Electrospray Ionization; Tandem Mass Spectrometry

The biotransformation of the two antiviral drugs, acyclovir (ACV) and penciclovir (PCV), was investigated in contact with activated sludge. Biodegradation kinetics were determined, and transformation products (TPs) were identified using Hybrid Linear Ion Trap- FT Mass Spectrometry (LTQ Orbitrap Velos) and 1D (1H NMR, 13C NMR) and 2D (1H,1H-COSY, 1H-(13)C-HSQC) NMR Spectroscopy. ACV and PCV rapidly dissipated in the activated sludge batch systems with half-lives of 5.3 and 3.4 h and first-order rate constants in relation to the amount of suspended solids (SS) of 4.9±0.1 L gss(-1) d(-1) and 7.6±0.3 L gss(-1) d(-1), respectively. For ACV only a single TP was found, whereas eight TPs were identified for PCV. Structural elucidation of TPs exhibited that transformation only took place at the side chain leaving the guanine moiety unaltered. The oxidation of the primary hydroxyl group in ACV resulted in the formation of carboxy-acyclovir (Carboxy-ACV). For PCV, transformation was more diverse with several enzymatic reactions taking place such as the oxidation of terminal hydroxyl groups and β-oxidation followed by acetate cleavage. Analysis of different environmental samples revealed the presence of Carboxy-ACV in surface and drinking water with concentrations up to 3200 ng L(-1) and 40 ng L(-1), respectively.

Topics: Acyclovir; Antiviral Agents; Biotransformation; Guanine; Sewage; Waste Disposal, Fluid; Water Pollutants, Chemical

Several kinds of food have been shown to influence the absorption and metabolism of drugs, although there is little information about their effect on the renal excretion of drugs. In this study, we performed uptake experiments using Xenopus laevis oocytes to assess the inhibitory effects of chlorogenic acid, caffeic acid and quinic acid, which are contained in coffee, fruits and vegetables, on human organic anion transporters hOAT1 and hOAT3; these transporters mediate renal tubular uptake of anionic drugs from blood. Injection of hOAT1 and hOAT3 cRNA into oocytes stimulated uptake of typical substrates of hOAT1 and hOAT3 (p-aminohippurate and estrone sulfate, respectively); among the three compounds tested, caffeic acid most strongly inhibited these transporters. The apparent 50% inhibitory concentrations of caffeic acid were estimated to be 16.6 µM for hOAT1 and 5.4 µM for hOAT3. Eadie-Hofstee plot analysis showed that caffeic acid inhibited both transporters in a competitive manner. In addition to the transport of p-aminohippurate and estrone sulfate, that of antifolates and antivirals was inhibited by caffeic acid. These findings show that caffeic acid has inhibitory potential against hOAT1 and hOAT3, suggesting that renal excretion of their substrates could be affected in patients consuming a diet including caffeic acid.

Topics: Acyclovir; Animals; Caffeic Acids; Chlorogenic Acid; Coffee; Estrone; Food-Drug Interactions; Fruit; Guanine; Humans; Inhibitory Concentration 50; Methotrexate; Oocytes; Organic Anion Transport Protein 1; Organic Anion Transporters, Sodium-Independent; p-Aminohippuric Acid; Quinic Acid; RNA, Complementary; Vegetables; Xenopus laevis

Studies to verify correlations between phenotypes and genotypes of herpes simplex virus (HSV) are an important tool to establish a database of resistance-associated mutations.. In this study, 32 acyclovir (ACV)-resistant clinical HSV-1 and 4 ACV-resistant clinical HSV-2 isolates were examined in parallel by both phenotypic and genotypic resistance testing. Additionally, five non-viable HSV-1 strains and two non-viable HSV-2 strains with clinical resistance were included in genotypic resistance analysis.. All ACV-resistant HSV isolates showed cross-resistance to brivudin and penciclovir, and were sensitive to foscarnet and cidofovir. Acyclovir resistance was assigned to frameshift and single non-synonymous mutations of the thymidine kinase (TK) gene in 32 out of 37 HSV-1 strains and in 4 out of 6 HSV-2 strains. In three HSV-1 isolates, there were resistance-associated amino acid substitutions of the DNA polymerase (pol). Six substitutions in the TK and two in the DNA pol gene could not be attributed without doubt to either ACV resistance or natural gene polymorphism. Altogether, 10 resistance-related mutations in the TK and 1 in the DNA pol gene have not been reported previously.. The novel non-synonymous mutations found in this study enrich the knowledge about the genetic alterations of TK and DNA pol genes in ACV-resistant clinical HSV strains. Together with data from the literature, the findings justify the generation of a HSV database that contains resistance mutations associated with ACV resistance phenotype.

Topics: Acyclovir; Adolescent; Adult; Aged; Antiviral Agents; Bromodeoxyuridine; Child; Child, Preschool; Cidofovir; Cytosine; DNA-Directed DNA Polymerase; Drug Resistance, Viral; Female; Foscarnet; Genotype; Guanine; Herpes Simplex; Herpesvirus 1, Human; Herpesvirus 2, Human; Humans; Infant; Male; Middle Aged; Mutation; Organophosphonates; Sequence Analysis, DNA; Thymidine Kinase; Viral Proteins

We investigated the pharmacokinetics of penciclovir after oral administration of its prodrug famciclovir to horses. Following an oral dose of famciclovir at 20 mg/kg, maximum plasma concentrations of penciclovir occurred between 0.75 and 1.5 hr (mean 0.94 + or - 0.38 hr) after dosing and were in the range 2.22 to 3.56 microg/ml (mean 2.87 + or - 0.61 microg/ml). The concentrations of penciclovir declined in a biphasic manner after the peak concentration was attained. The mean half-life of the rapid elimination phase was 1.73 + or - 0.34 hr whereas that of the slow elimination phase was 34.34 + or - 13.93 hr. These pharmacokinetic profiles observed were similar to those of another antiherpesvirus drug, acyclovir, previously reported in horses following oral dosing of its prodrug valacyclovir.

Topics: 2-Aminopurine; Acyclovir; Administration, Oral; Animals; Antiviral Agents; Area Under Curve; Famciclovir; Guanine; Half-Life; Herpesviridae Infections; Herpesvirus 1, Equid; Horse Diseases; Horses

Nucleoside analogs are efficacious cancer chemotherapeutics due to their incorporation into tumor cell DNA. However, they exhibit vastly different antitumor efficacies, suggesting that incorporation produces divergent effects on DNA replication. Here we have evaluated the consequences of incorporation on DNA replication and its fidelity for three structurally related deoxyguanosine analogs: ganciclovir (GCV), currently in clinical trials in a suicide gene therapy approach for cancer, D-carbocyclic 2'-deoxyguanosine (CdG) and penciclovir (PCV). GCV and CdG elicited similar cytotoxicity at low concentrations, whereas PCV was 10-100-fold less cytotoxic in human tumor cells. DNA replication fidelity was evaluated using a supF plasmid-based mutation assay. Only GCV induced a dose-dependent increase in mutation frequency, predominantly GC-->TA transversions, which contributed to cytotoxicity and implicated the ether oxygen in mutagenicity. Activation of mismatch repair with hydroxyurea decreased mutations but failed to repair the GC-->TA transversions. GCV slowed S-phase progression and CdG also induced a G2/M block, but both drugs allowed completion of one cell cycle after drug treatment followed by cell death in the second cell cycle. In contrast, PCV induced a lengthy early S-phase block due to profound suppression of DNA synthesis, with cell death in the first cell cycle after drug treatment. These data suggest that GCV and CdG elicit superior cytotoxicity due to their effects in template DNA, whereas strong inhibition of nascent strand synthesis by PCV may protect against cytotoxicity. Nucleoside analogs based on the carbohydrate structures of GCV and CdG is a promising area for antitumor drug development.

Topics: Acyclovir; Antineoplastic Agents; Base Sequence; Carbohydrates; Cell Cycle; Cell Death; Cell Line, Tumor; Deoxyguanosine; DNA Mismatch Repair; DNA Replication; Ganciclovir; Genes, Transgenic, Suicide; Guanine; HCT116 Cells; Humans; Molecular Sequence Data; Mutation

Sixteen herpes simplex virus type 1 (HSV-1) and four type 2 (HSV-2) isolates resistant to acyclovir (ACV) were characterized retrospectively for drug resistance. Phenotypic testing was performed by means of tetrazolium reduction assay and genotypic analysis was carried out by sequencing of thymidine kinase (TK) and DNA-polymerase (pol) genes. All strains were characterized as cross-resistant to penciclovir, brivudin and susceptible to cidofovir. In addition, three strains were resistant to foscarnet. Genotypic analysis revealed two to seven non-synonymous mutations in the TK gene of HSV-1 and one to seven non-synonymous mutations in the DNA pol gene of HSV-1 and 2 associated with the gene polymorphism. Seventeen strains contained at least one non-synonymous resistant-related mutation in the TK gene and three strains, which were additionally foscarnet-resistant, revealed one resistance-associated mutation in the DNA pol gene. In most strains, resistant-related mutations in TK gene represented frameshift mutations and single non-synonymous nucleotide substitutions of conserved gene regions. However, numerous amino acid changes could not be interpreted clearly as accounting for resistance. In conclusion, further studies, e.g. site-directed mutagenesis experiments are required to characterize mutations of the TK and DNA pol genes in ACV-resistant viral strains as part of viral gene polymorphism or as cause of drug resistance.

Topics: Acyclovir; Animals; Antiviral Agents; Bromodeoxyuridine; Cell Survival; Cells, Cultured; Cidofovir; Cytosine; DNA-Directed DNA Polymerase; Drug Resistance, Viral; Exodeoxyribonucleases; Foscarnet; Guanine; Herpesvirus 1, Human; Herpesvirus 2, Human; Humans; Microbial Sensitivity Tests; Mutation, Missense; Organophosphonates; Oxidation-Reduction; Sequence Analysis, DNA; Staining and Labeling; Tetrazolium Salts; Thymidine Kinase; Viral Proteins

The purpose of the present study was to investigate the skin irritation and pharmacodynamics of penciclovir-loaded microemulsion (PCV-ME). The formulation of PCV-ME was comprised of oleic acid (OA) (5%, w/w), Cremorphor EL (20%, w/w), ethanol (30%, w/w) and water (45%, w/w). PCV-ME presented as spherically shaped under transmission electron microscopy with an average diameter of 36.5 nm, and the solubility of PCV in microemulsion (ME) was 7.41 mg/g, almost 6 times that in water. Skin irritation test was performed in male guinea pigs, which demonstrated that no irritation effect was caused after single or multiple applications of PCV-ME. Likewise, male guinea pigs were employed as animal models which were infected with herpes simplex virus type 1 (HSV-1) in pharmacodynamics study. Real-time PCR was utilized to investigate the inhibition effect on HSV-1 exerted by commercial PCV-cream and PCV-ME. The results indicated that compared with commercial PCV-cream, PCV-ME could significantly inhibit the replication of HSV-1 in skin. In conclusion, PCV-ME could be a promising formulation which possessed the virtues of low irritation and high effectiveness.

Topics: Acyclovir; Animals; Antiviral Agents; Cell Line, Tumor; Emulsions; Guanine; Guinea Pigs; Herpes Simplex; Herpesvirus 1, Human; Humans; Male; Skin; Skin Irritancy Tests

Non-invasive in vivo imaging of transgene expression is currently providing very important means to optimize gene therapy regimes. Results in non-human primates are considered the most predictive models for the outcome in patients. In this study, we have documented that tumour and primary cell lines from human and non-human primates are comparably gene-transduced in vitro by serotype 5 adenovirus expressing HSV1-thymidine kinase. Transgene expression can be quantified in human and monkey cultured cells by positron emission tomography (PET) imaging when transduced cells are incubated with a fluoride-18 labelled penciclovir analogue. In our hands, PET images of cell cultures estimate the number of transduced cells rather than intensity of transgene expression once a threshold of TK per cell is reached. Interestingly, in vivo systemic administration of a clinical grade recombinant adenovirus expressing TK into macaques gives rise to an intense retention of the radiotracer in the liver parenchyma, providing an experimental system to visualize transgene expression that ought to be similar in human and macaques. Such imaging methodology might contribute to improve strategies based on adenoviral vectors.

Topics: Acyclovir; Adenoviridae; Animals; Cell Count; Cell Line, Transformed; Gene Expression; Genetic Therapy; Genetic Vectors; Guanine; Herpesvirus 1, Human; Humans; Injections, Intravenous; Liver; Macaca; Models, Animal; Positron-Emission Tomography; Radiopharmaceuticals; Thymidine Kinase; Transduction, Genetic; Transgenes

The ability to achieve tumor selective expression of therapeutic genes is an area that needs improvement for cancer gene therapy to be successful. One approach to address this is through the use of promoters that can be controlled by external means, such as hyperthermia. In this regard, we constructed a replication-deficient adenovirus that consists of a mutated herpes simplex virus 1 thymidine kinase (mTK) fused to enhanced green fluorescent protein (EGFP) under the control of the full-length human heat shock (HS) 70b promoter. The virus (AdHSmTK-EGFP) was evaluated both in vitro and in vivo in oral squamous cell carcinoma SCC-9 cells for expression of both mTK and EGFP. The in vitro expression of mTK-EGFP was validated using both (3)H-penciclovir and fluorescence-activated cell sorting assays. These studies show that specific expression could be achieved by heating the cells at 41 degrees C for 1 h, whereas little expression was observed using high doses of virus without hyperthermia. The vector was also evaluated in vivo by direct intratumoral injection into mice bearing SCC-9 xenografts. These studies demonstrated tumor expression of mTK-EGFP after ultrasound heating of the tumors by radioactive biodistribution assays, histology and microPET imaging. These in vivo results, which demonstrate HS-inducible transgene expression using PET imaging, provide a means for noninvasive monitoring of heat-induced gene therapy in local tumors, such as oral squamous cell carcinomas.

Topics: Acyclovir; Adenoviridae; Animals; Antiviral Agents; Carcinoma, Squamous Cell; Cell Line, Tumor; Flow Cytometry; Gene Expression Regulation; Genes, Transgenic, Suicide; Genetic Vectors; Guanine; Head and Neck Neoplasms; Heat-Shock Proteins; Hot Temperature; Humans; Liver; Mice; Mice, SCID; Positron-Emission Tomography; Transplantation, Heterologous

Herpes simplex virus infection (HSV) is a common and ubiquitous infection of the skin which causes mucocutaneous lesions called cold sores (herpes labialis) or fever blisters. It is estimated that approximately 80% of the population worldwide are carriers of the Herpes simplex virus, approximately 40% suffer from recurrent recurrent infections. This study evaluates the in vitro skin permeation and penetration of penciclovir and acyclovir from commercialized creams for the treatment of herpes labialis (cold sores), using non viable excised human abdominal skin samples, which were exposed to 5 mg/cm2 of acyclovir 5% cream or penciclovir 1% cream.. After 24 h of cream application, excess cream was washed off and layers of stratum corneum were removed by successive tape stripping. Amounts of active ingredients having penetrated through the skin were measured, as well as the amounts in the washed-off cream, in skin strips and creams remaining in the skin. Molecular modelling was used to evaluate physico-chemical differences between the drugs. Western blot analysis enabled to determine whether the marker of basal cells keratin 5 could be detected in the various tape strips.. Application of penciclovir 1% cream yielded higher concentration of drug in the deeper layers of the epidermis as well as a higher drug flux through the skin. Molecular modelling showed two higher hydrophobic moieties for acyclovir. Presence of the basal cell marker keratin 5 was underscored in the deeper tape strips from the skin, giving evidence that both drugs can reach their target cells.. Penciclovir 1% cream has the tendency to facilitate the diffusion of the drug through the stratum corneum into the deeper epidermis layers, in which it could reach the target basal cells at effective therapeutical concentration. The small difference in the surface properties between both molecules might also contribute to favour the passage of penciclovir through the epidermis into the deeper basal cells.

Topics: Abdomen; Acyclovir; Antiviral Agents; Dermis; Diffusion; Drug Evaluation, Preclinical; Epidermis; Gene Expression Regulation; Guanine; Herpes Simplex; Humans; Hydrophobic and Hydrophilic Interactions; In Vitro Techniques; Keratin-5; Ointments; Permeability; Skin Absorption

The objective of this investigation was to develop solid lipid nanoparticles (SLNs) of penciclovir and evaluate the potential of SLNs as the carrier of penciclovir for topical delivery. Penciclovir-loaded SLNs were prepared by a double (W/O/W) emulsion technique. The SLNs presented spherical with the mean diameter of 254.9 nm. The entrapment efficiency, drug loading and zeta potential were 92.40%, 4.62% and -25.0 mV, respectively. DSC study showed that penciclovir encapsulated in SLNs was in the amorphous form. The cumulative amount of penciclovir penetrated through excised rat skin from SLNs was more than 2-fold that of the commercial cream as a control at 12h after administration. There was no significant difference of penciclovir content deposited in epidermis between the cream and SLNs administrated for 2, 6 and 12h, while SLNs increased the cumulative uptake of penciclovir in dermis significantly at the same intervals. Microscopic pictures showed that the interaction between SLNs and the skin surface changed the apparent morphology of stratum corneum and broke the close conjugation of corneocyte layers, which was the possible reason that SLNs increased the permeation of penciclovir into skin dermis. It can be concluded from our study that SLNs provide a good skin targeting effect and may be a promising carrier for topical delivery of penciclovir.

Topics: Acyclovir; Administration, Topical; Animals; Drug Delivery Systems; Drug Evaluation, Preclinical; Guanine; In Vitro Techniques; Male; Nanoparticles; Particle Size; Rats; Rats, Wistar; Skin Absorption

The purpose of this study was to investigate microemulsion-based hydrogel (MBH) as a topical delivery system for penciclovir. Topical delivery of penciclovir in the forms of microemulsion, MBH and the commercial cream was evaluated in vitro and in vivo. The results of permeation test in vivo in mice showed that compared with the commercial cream, MBH and microemulsion could significantly increase the permeation of penciclovir into both epidermis and dermis. Stability test showed that MBH stored at 4 degrees C for 3 months had no significant change in physicochemical properties. Skin irritation test in rabbit demonstrated that single application or multiple applications of MBH did not cause any erythema or edema, slight skin irritation for microemulsion. Microstructure changes of skins after administration observed under light microscope and scanning electron microscope (SEM) might result from the interaction of the ingredients of microemulsion with skins, which was related with the permeation enhancement of penciclovir. It can be concluded that the MBH could be a promising vehicle for topical delivery of penciclovir.

Topics: Acyclovir; Administration, Cutaneous; Animals; Antiviral Agents; Chemistry, Pharmaceutical; Dermis; Drug Stability; Drug Storage; Emulsions; Epidermis; Guanine; Hydrogels; Male; Mice; Microscopy; Microscopy, Electron, Scanning; Propylene Glycol; Rabbits; Skin Absorption; Skin Irritancy Tests

Monkey B virus (Macacine herpesvirus 1; BV) is an alpha-herpesvirus of macaques that causes serious infections in humans. A spontaneous mutant resistant to penciclovir (PCV) was isolated. Several genes were sequenced to identify mutations potentially responsible for PCV resistance. A single nucleotide deletion in the thymidine kinase (TK) gene was identified. To confirm its role in PCV resistance, several TK recombinants were constructed. A TK-deletion virus and a recombinant carrying the mutation were both resistant to PCV, while a revertant was PCV-sensitive. These results demonstrate that spontaneous drug-resistant mutants of BV do occur and that the BV TK is responsible for sensitivity to PCV.

Topics: Acyclovir; Animals; Drug Resistance, Viral; Guanine; Herpesvirus 1, Cercopithecine; Humans; Mutation; Reverse Transcriptase Inhibitors; Thymidine Kinase; Viral Proteins

The purpose of the present study was to evaluate the potential application of microemulsions as a dermal drug delivery loading penciclovir. The pseudo-ternary phase diagrams were developed for various microemulsion formulations composed of oleic acid (oil phase), Cremorphor EL (surfactant) and ethanol (cosurfactant). Composition of microemulsion systems was optimized using simplex lattice mixture design including the concentrations of surfactant, cosurfactant and water (independent variables) and the solubility and the cumulative amount of penciclovir permeated through excised mouse skins per unit area (response variables). The physicochemical properties of the optimized microemulsion and the permeating ability of penciclovir from microemulsions were also investigated. The results showed that the optimized microemusion formulation was composed of oleic acid (5%, w/w), Cremorphor EL (20%, w/w), ethanol (30%, w/w) and water (45%, w/w). The mean particle diameter was 36.5nm and solubility of penciclovir in the emulsion was 7.41 mg g(-1). The cumulative amount of penciclovir permeated through excised mouse skins from microemulsion was about 3.5 times that of the commercial cream. The conclusion was that the permeating ability of penciclovir was significantly increased from the microemulsion formulation compared with commercial cream.

Topics: Acyclovir; Algorithms; Animals; Antiviral Agents; Chemistry, Pharmaceutical; Diffusion Chambers, Culture; Drug Design; Emulsions; Ethanol; Glycerol; Guanine; Male; Mice; Oils; Skin Absorption; Surface-Active Agents; Water

A simple, specific, and accurate high-performance liquid chromatographic method, using UV detection for the determination of penciclovir in human plasma, is described. Chromatographic separation is performed on a BDS-C(18) column using a mixture of phosphate buffer (20mM, pH adjusted to 7.5 with phosphoric acid), methanol, and acetonitrile (94:3:3, v/v/v) as mobile phase. The wavelength of the UV detector is set at 254 nm. The flow-rate is 1.0 mL/min. The assay is linear over the concentration range of 0.1-5.0 microg/mL for penciclovir (r > 0.9996). The limit of quantitation for penciclovir in human plasma is 0.1 microg/mL. The relative standard deviation is less than 7.0% for all the analytes. The method is successfully applied to a randomized crossover bioequivalence study of two different famciclovir capsules in 20 healthy volunteers.

Topics: Acyclovir; Chromatography, High Pressure Liquid; Guanine; Humans; Therapeutic Equivalency

Feline herpesvirus-1 (FHV-1) causes a severe upper respiratory and ocular disease in cats. An effective antiviral compound is required for treating FHV-1 infections. The virus-encoded thymidine kinase (TK) is the molecular basis for selective activation of commonly used antiviral nucleoside analogue drugs, e.g. acyclovir (ACV), penciclovir (PCV) and ganciclovir (GCV). The substrate specificity of a recombinant FHV-1 TK, expressed in Escherichia coli, was studied. FHV-1 TK efficiently phosphorylated its natural substrate deoxythymidine. However, it exhibited relatively lower affinity for the guanosine analogue substrates. PCV was most efficiently phosphorylated, followed by GCV, with approximately twofold reduction in the phosphorylation rate. The lowest phosphorylation rate was recorded for ACV. To correlate these biochemical data with structural features of the FHV-1 TK, a three-dimensional (3D) model of this enzyme was constructed based on sequence homology with two other herpesviral TKs, encoded by equine herpesvirus-4 (EHV-4) and herpes simplex-1 (HSV-1). Mutational analysis of the amino acids forming the FHV-1 TK active site identified two residues (Y29 and F144) as being critical for the differential ability of this enzyme to phosphorylate nucleoside analogues. A double substitution of Y29H/F144Y resulted in a threefold increase in the ACV phosphorylation rate.

Topics: Acyclovir; Animals; Antiviral Agents; Cats; Cloning, Molecular; Ganciclovir; Guanine; Hydrogen Bonding; Models, Molecular; Mutagenesis, Site-Directed; Phosphorylation; Protein Conformation; Protein Structure, Secondary; Substrate Specificity; Thymidine; Thymidine Kinase; Varicellovirus

Feline herpesvirus-1 (FHV-1) is the causative agent of a severe ocular disease in cats for which a safe potent antiviral chemotherapeutic agent is highly demanded. The sensitivity of FHV-1 to inhibition by three anti-herpetic nucleoside analogues [acyclovir (ACV), penciclovir (PCV) and cidofovir (CDV)] was tested by means of yield reduction assay. ACV showed very poor ability to inhibit FHV-1 replication. At low multiplicity of infection (MOI), both PCV and CDV were nearly equally effective with IC50 values ranging between 6 and 8 microg/ml. However, when the MOI was raised to 3PFU/cell, the activity of CDV was markedly reduced (IC50 25 microg/ml), while that of PCV remained relatively low (IC50 10 microg/ml). Although FHV-1 is normally insensitive to ACV, it exhibited >1000-fold increase in sensitivity when the thymidine kinase (TK) encoded by herpes simplex virus-1 (HSV-1) was supplied in trans. Furthermore, three PCV-resistant FHV-1 variants selected in vitro were shown to carry mutations in the TK gene. Taken together, these data provided direct evidence that PCV is a potent selective inhibitor of FHV-1 and that the virus-encoded TK is an important determinant of the virus susceptibility to nucleoside analogues.

Topics: Acyclovir; Animals; Antiviral Agents; Cats; Cell Line; Drug Resistance, Viral; Guanine; Herpesvirus 1, Human; Inhibitory Concentration 50; Kidney; Microbial Sensitivity Tests; Mutation; Thymidine Kinase; Virus Replication

A fast, simple and selective HPLC method has been developed for the assay of aciclovir, ganciclovir, and penciclovir in human plasma by coupling HPLC with fluorescence detection. 200 microl plasma, with guanosine 5'-monophosphate as an internal standard, was subjected to protein precipitation with a 7% [v/v] aqueous perchloric acid solution. The 40 microl supernatant was injected into a Diamonsil-5 microm C18 column. Aciclovir, ganciclovir, and penciclovir, with solvents composed of methanol and 0.08% aqueous trifluoroacetic acid solution, were analysed by fluorescence detection at 260 nm (excitation) and 380 nm (emission) using a gradient elution program. The calibration curves of all three analytes were linear between 20 and 2000 ng/ml. The mean absolute recoveries of aciclovir, ganciclovir, and penciclovir were 93.91+/-1.20%, 97.42+/-0.75%, and 99.01+/-3.30%, respectively. The mean inter-day CVs for aciclovir, ganciclovir, and penciclovir, were within 1.29-7.30%, 1.00-5.53%, and 1.19-3.54%, respectively. The intra-day bias for aciclovir, ganciclovir, and penciclovir ranged from -2.01 to 6.33%, 1.81 to 7.37%, and 1.42 to 6.91%, respectively. The method has been validated and applied in pharmacokinetic studies in Chinese adult renal transplant patients.

Topics: Acyclovir; Antiviral Agents; Calibration; Chromatography, High Pressure Liquid; Ganciclovir; Guanine; Humans; Reference Standards; Reproducibility of Results; Sensitivity and Specificity; Spectrometry, Fluorescence

Herpes B virus (B virus [BV]) is a macaque herpesvirus that is occasionally transmitted to humans where it can cause rapidly ascending encephalitis that is often fatal. To understand the low susceptibility of BV to the acyclonucleosides, we have cloned, expressed, and characterized the BV thymidine kinase (TK), an enzyme that is expected to "activate" nucleoside analogs. This enzyme is similar in sequence and properties to the TK of herpes simplex virus (HSV), i.e., it has a broad substrate range and low enantioselectivity and is sensitive to inhibitors of HSV TKs. The BV enzyme phosphorylates some modified nucleosides and acyclonucleosides and l enantiomers of thymidine and related antiherpetic analogs. However, the potent anti-HSV drugs acyclovir (ACV), ganciclovir (GCV), and 5-bromovinyldeoxyuridine were poorly or not phosphorylated by the BV enzyme under the experimental conditions. The antiviral activities of a number of marketed antiherpes drugs and experimental compounds were compared against BV strains and, for comparison, HSV type 1 (HSV-1) in Vero cell cultures. For most compounds tested, BV was found to be about as sensitive as HSV-1 was. However, BV was less sensitive to ACV and GCV than HSV-1 was. The abilities of thymidine analogs and acyclonucleosides to inhibit replication of BV in Vero cell culture were not always proportional to their substrate properties for BV TK. Our studies characterize BV TK for the first time and suggest new lead compounds, e.g., 5-ethyldeoxyuridine and pencyclovir, which may be superior to ACV or GCV as treatment for this emerging infectious disease.

Topics: Acyclovir; Amino Acid Sequence; Animals; Antiviral Agents; Chlorocebus aethiops; Deoxyuridine; Enzyme Inhibitors; Guanine; Herpesvirus 1, Cercopithecine; Microbial Sensitivity Tests; Molecular Sequence Data; Nucleosides; Phosphorylation; Substrate Specificity; Thymidine; Thymidine Kinase; Vero Cells

To identify factors that contribute to variability of HSV antiviral susceptibility breakpoints.. Acyclovir and penciclovir IC(50)'s for 12 HSV clinical isolates were measured in two laboratories using plaque reduction assay (PRA), an enzyme immunoassay (EIA)-based antigen reduction, and DNA hybridization on Vero, A549, MRC-5, HEL299 and HELG monolayers. Pair-wise comparisons were performed to evaluate variables including testing laboratory, technique, monolayer, and antiviral. The proportion of false results was analyzed using a conventional susceptibility IC(50) breakpoint of 2 microg/ml.. Acyclovir-resistant HSV isolates were correctly identified by all methods. In contrast, there were 6-67% of susceptible isolates incorrectly characterized as drug-resistant. Variables associated with these errors included testing site, assay method, cell line and antiviral. A549, DNA hybridization, and penciclovir were associated with the highest IC(50)'s, whereas the PRA, EIA, and human fibroblast-monolayers provided the best differentiation between susceptible and resistant HSV isolates.. The current recommendations to use a single discriminating value to define HSV resistance to nucleoside analogues can be problematic. False results are influenced in various degrees by the laboratory method, tissue culture and antivirals.

Topics: Acyclovir; Animals; Antiviral Agents; Cell Culture Techniques; Chlorocebus aethiops; Drug Resistance, Viral; Fibroblasts; Guanine; Herpesvirus 1, Human; Herpesvirus 2, Human; Humans; Immunoenzyme Techniques; Inhibitory Concentration 50; Nucleic Acid Hybridization; Vero Cells; Viral Plaque Assay

We developed and validated a simple high-performance liquid chromatography (HPLC) coupled with positive ion electrospray ionization tandem mass spectrometry (ESI-MS/MS) detection system for determining penciclovir (active metabolite of famciclovir) levels in human plasma using acyclovir as an internal standard (IS). Acquisition was performed in multiple reaction monitoring (MRM) mode by monitoring the transitions: m/z 254.00>152.09 for penciclovir and m/z 226.00>152.09 for IS. The analytes were chromatographed on a Capcellpak MGII C(18) reversed-phase chromatographic column by isocratic elution using 30% methanol and 70% Milli-Q water containing 10 mM ammonium formate (adjusted to pH 3.1 with formic acid). Results were linear over the studied range (0.05-10 microg/ml) with r(2)=0.9999, and the total analysis time for each run was 2 min. Intra- and inter-assay precisions were 2.3-7.8 and 3.7-7.5%, respectively, and intra- and inter-assay relative errors (RE) were 2.0-8.4 and 1.9-9.1%, respectively. The lower limit of quantification (LLOQ) was 0.05 microg/ml. At this concentration mean intra- and inter-assay precisions were 7.8 and 7.5%, respectively, and mean intra- and inter-assay relative errors were 2.2 and 9.1%, respectively. Penciclovir was found to be stable in plasma samples under short-, long-term storage and processing conditions. The developed assay was successfully applied to a bioequivalence study of penciclovir administered as a single oral dose (500 mg as famciclovir) to healthy volunteers.

Topics: Acyclovir; Antiviral Agents; Chromatography, High Pressure Liquid; Guanine; Humans; Male; Reproducibility of Results; Sensitivity and Specificity; Tandem Mass Spectrometry; Therapeutic Equivalency

The influence of the thymidine (Thd) kinase (TK) of herpes simplex virus type 1 (HSV-1) on the intracellular uptake and anabolism of nucleosides has been investigated. To compare the differences between the TK-positive (TK(+)) and TK-deficient strains, acyclovir (ACV)-resistant strains were cloned from a cell culture and classified into 2 groups, viz. the TK-partial (TK(p)) and TK-negative (TK(-)). The cellular uptake of thymidine was highly dependent on the viral TK (vTK) activity. The TK(+) strain showed the highest level of intracellular thymidine uptake, the TK(p) strain a moderate level, which varied from strain to strain, and the TK(-) and mock strains showed little uptake. The inhibition of viral replication by ACV, ganciclovir (GCV) and penciclovir (PCV) did not decrease the Thd uptake at all. On the contrary, a notable increase found to be induced by ACV. The influence of the vTK on the uptake of GCV or PCV was much greater than that of ACV. The metabolism was generally less dependent on the vTK activity than the influx. The influx and phosphorylation rates of GCV and PCV were dependent on the substrate specificity of the vTK.

Topics: Acyclovir; Animals; Antiviral Agents; Cell Line, Tumor; Chlorocebus aethiops; DNA; DNA, Viral; Drug Resistance, Viral; Ganciclovir; Guanine; Herpesvirus 1, Human; Humans; Mutation; Substrate Specificity; Thymidine; Thymidine Kinase; Vero Cells

We have established practical synthetic methods for penciclovir (PCV, 1) and famciclovir (FCV, 2) from N2-acetyl-7-benzylguanine (NAc7BnG, 3) and 6,6-dimethyl-5, 7-dioxaspiro[2.5]octane-4,8-dione (4)--the latter being a more easily prepared cyclic precursor of the diacetate side chain (5) used in the conventional process. The coupling of 4 with 3 proceeded regioselectively at the N9 position of guanine in good yield. The coupling product was then successfully transformed into the known antiviral agents in a short number of steps.

Topics: 2-Aminopurine; Acyclovir; Antiviral Agents; Famciclovir; Guanine; Molecular Structure; Prodrugs

Topics: 2-Aminopurine; Acyclovir; Antiviral Agents; Cytomegalovirus Infections; Drug Resistance, Viral; Famciclovir; Guanine; Hepatitis B; Hepatitis C; Herpes Simplex; Herpes Zoster; Humans; Influenza, Human; Valacyclovir; Valine; Virus Diseases

The compounds [Pt(Me(2)phen)(acy)(2)](NO(3))(2) (1), [Pt(Me(2)phen)(pen)(2)](NO(3))(2), [Pt(phen)(acy)(2)](NO(3))(2) (2), and [Pt(phen)(pen)(2)](NO(3))(2), containing the bidentate 1,10-phenanthroline (phen) or 2,9-dimethyl-1,10-phenanthroline (Me(2)phen, neocuproine) and the antiviral agents acyclovir (acy) or penciclovir (pen), show different in vitro toxicity, the Me(2)phen complexes being appreciably more toxic than the phen complexes. To explain the different behavior, we investigated the reaction of complexes 1 and 2 with glutathione (gamma-glutamylcysteinylglycine, GSH), a peptide believed to play an important role in driving the cellular effects of platinum drugs. The reaction led to different products, the phen complexes forming a stable binuclear mu-thiol-bridged species still containing the phenanthroline and the Me(2)phen complexes releasing the neocuproine ligand and forming an insoluble material. In vitro tests confirmed that the greater cell toxicity of complex 1 is due to the displacement of the neocuproine ligand by GSH. The results highlight the great dependence of the glutathione reactivity upon relatively small changes in the platinum coordination sphere.

Topics: Acyclovir; Animals; Antineoplastic Agents; Antiviral Agents; Cell Line, Tumor; Cell Proliferation; Drug Screening Assays, Antitumor; Glutathione; Guanine; Mice; Organoplatinum Compounds; Phenanthrolines

Herpes simplex virus type 2 (HSV-2) resistance to antiviral drugs has been described primarily in immunocompromised patients. We report an apparently immunocompetent, human immunodeficiency virus-negative male patient who has experienced repeated HSV-2 genital outbreaks despite receiving antiviral prophylaxis with several different drugs. Several of the HSV-2 genital isolates from this patient have been confirmed as resistant to acyclovir and penciclovir. Antiviral resistance occurred in the setting of long-term prednisone treatment and intermittent acyclovir prophylaxis at suboptimal doses and persisted despite the cessation of oral steroid treatment. The patient's genital herpes outbreaks were not controlled by high-dose prophylaxis with acyclovir, valacyclovir, and famciclovir. Cessation of antiviral prophylaxis resulted in reversion of this patient's HSV-2 isolates to acyclovir and penciclovir sensitivity, although resistant virus reappeared when antiviral prophylaxis was resumed. Transmission of a sensitive HSV-2 strain from this patient to a female sex partner was observed. These observations confirm previous reports that resistance to acyclovir may develop during prophylactic therapy in an otherwise well, immunocompetent patient. These findings support the conclusion that both drug-sensitive and drug-resistant HSV-2 strains established latency in this patient and that both strains are capable of frequent reactivation.

Topics: Acyclovir; Adult; Antiviral Agents; Drug Resistance, Multiple, Viral; Female; Guanine; Herpes Genitalis; Herpesvirus 2, Human; Humans; Immunocompetence; Male; Recurrence

Human cytomegalovirus (HCMV) resistance to antivirals is a significant clinical problem. Murine cytomegalovirus (MCMV) infection of mice is a well-described animal model for in vivo studies of CMV pathogenesis, although the mechanisms of MCMV antiviral susceptibility need elucidation. Mutants resistant to nucleoside analogues aciclovir, adefovir, cidofovir, ganciclovir, penciclovir and valaciclovir, and the pyrophosphate analogue foscarnet were generated by in vitro passage of MCMV (Smith) in increasing concentrations of antiviral. All MCMV antiviral resistant mutants contained DNA polymerase mutations identical or similar to HCMV DNA polymerase mutations known to confer antiviral resistance. Mapping of the mutations onto an MCMV DNA polymerase three-dimensional model generated using the Thermococcus gorgonarius Tgo polymerase crystal structure showed that the DNA polymerase mutations potentially confer resistance through changes in regions surrounding a catalytic aspartate triad. The ganciclovir-, penciclovir- and valaciclovir-resistant isolates also contained mutations within MCMV M97 identical or similar to recognized GCV-resistant mutations of HCMV UL97 protein kinase, and demonstrated cross-resistance to antivirals of the same class. This strongly suggests that MCMV M97 has a similar role to HCMV UL97 in the phosphorylation of nucleoside analogue antivirals. All MCMV mutants demonstrated replication-impaired phenotypes, with the lowest titre and plaque size observed for isolates containing mutations in both DNA polymerase and M97. These findings indicate DNA polymerase and protein kinase regions of potential importance for antiviral susceptibility and replication. The similarities between MCMV and HCMV mutations that arise under antiviral selective pressure increase the utility of MCMV as a model for in vivo studies of CMV antiviral resistance.

Topics: Acyclovir; Adenine; Animals; Antiviral Agents; Cidofovir; Cytomegalovirus; Cytosine; DNA-Directed DNA Polymerase; Drug Resistance, Viral; Ganciclovir; Guanine; Humans; Mice; Models, Molecular; Molecular Sequence Data; Muromegalovirus; Mutation; Organophosphonates; Protein Kinases; Sequence Alignment; Valacyclovir; Valine; Virus Replication

A simple, sensitive and reliable HPLC ion-pairing method with fluorescence detection, was developed for penciclovir determination in plasma and aqueous humor, with a Zorbax SB-aq C18 (100 mmx2.1 mm) column. Plasma samples were treated by solid-phase extraction with Oasis MCX (30 mg) cartridges. Ganciclovir, an antiviral drug structurally related to penciclovir, was used as internal standard (I.S.). Aqueous humor samples were directly injected into the chromatographic system. Separation was performed by a gradient elution with a mobile phase consisting of a mixture of acetonitrile and phosphate buffer 50mM containing 5mM of sodium octanesulfonate, pH 2.0, at a flow rate of 0.3 ml/min. The method was validated and showed good performances in terms of linearity, sensitivity, precision and trueness. Quantification limit was obtained at 0.05 microg/ml for aqueous humor and at 0.1 microg/ml for plasma. Finally, the proposed analytical method was used to measure penciclovir in clinical samples for a pharmacokinetic study, after oral administration of famciclovir.

Topics: Acyclovir; Aqueous Humor; Chromatography, High Pressure Liquid; Drug Stability; Ganciclovir; Guanine; Humans; Hydrogen-Ion Concentration; Reproducibility of Results; Sensitivity and Specificity; Spectrometry, Fluorescence; Temperature

The solubility of penciclovir (C(10)N(5)O(3)H(17)) in a novel film formulation designed for the treatment of cold sores was determined using X-ray, thermal, microscopic and release rate techniques. Solubilities of 0.15-0.23, 0.44, 0.53 and 0.42% (w/w) resulted for each procedure. Linear calibration lines were achieved for experimentally and theoretically determined differential scanning calorimetry (DSC) and X-ray powder diffractometry (XRPD) data. Intra- and inter-batch data precision values were determined; intra values were more precise. Microscopy was additionally useful for examining crystal shape, size distribution and homogeneity of drug distribution within the film. Whereas DSC also determined melting point, XRPD identified polymorphs and release data provided relevant kinetics.

Topics: Acyclovir; Calorimetry, Differential Scanning; Guanine; Microscopy, Confocal; Polymethacrylic Acids; Solubility; X-Ray Diffraction

A heterogeneous herpes simplex virus type 2 (HSV-2) population was characterised from an AIDS patient with relapsing genital ulcer. The isolate had an unusual antiviral spectrum, showing resistance to penciclovir and susceptibility to acyclovir. Two viral populations were plaque purified, one resistant and the other susceptible to both antiviral drugs. The resistant clone was deficient in thymidine kinase (TK) activity and a nucleotide substitution, thymine for cytosine, at position 153 was identified in its TK gene. This mutation resulted in an amino acid change, arginine to tryptophan, in the ATP binding site. In the deficient mutant, a loss of virulence was observed in mice.

Topics: Acquired Immunodeficiency Syndrome; Acyclovir; Amino Acid Substitution; Animals; Antiviral Agents; Base Sequence; Chlorocebus aethiops; DNA, Viral; Drug Resistance, Viral; Female; Genes, Viral; Guanine; Herpes Genitalis; Herpesvirus 2, Human; Humans; Male; Mice; Thymidine Kinase; Vero Cells; Virulence

tert-Azido or amino substituted penciclovir analogs, 1-3 were synthesized for the purpose of improving the efficacy and bioavailability of penciclovir and searching for novel antiviral agents. Among several methods attempted to insert an azido group into the alpha,beta-unsaturated ester 6, only Bronsted acid-catalysed 1,4-conjugate addition conditions (NaN3, 75% acetic acid, 80 degrees C) gave the desired tert-azido product 7. The synthesized final penciclovir analogs 1-3 were evaluated in vitro against several viruses such as HIV-1, HSV-1 and 2, poliovirus, VZV, and VSV. Compound 2 only showed weak antiviral activity against HSV-1 without cytotoxicity. Although the synthesized compounds did not exhibit an excellent antiviral activity, the successful method used in introducing the tert-azido group is expected to be generally utilized for the synthesis of nucleoside analogs with a tert-azido substituent.

Topics: Acyclovir; Amines; Antiviral Agents; Azides; Catalysis; Cell Line; Guanine; HIV-1; HIV-2; Microbial Sensitivity Tests; Poliovirus; Simplexvirus

To establish the in vitro efficacy of 4 novel drugs (ie, ganciclovir, cidofovir, penciclovir, and foscarnet) against feline herpesvirus type-1 (FHV-1) and compare their antiviral efficacy with that of acyclovir and idoxuridine.. Cultured Crandell-Reese feline kidney (CRFK) cells and FHV-1 strain 727. For each drug, antiviral effect was estimated by use of conventional plaque-reduction assays, and inhibitory concentration 50 (IC50; drug concentration at which plaque numbers were reduced by 50% relative to the number of plaques for nontreated control wells) was calculated. To determine whether observed antiviral effects were related to alterations in the number or viability of CRFK cells, cytotoxicity assays were performed at 1, 2, and 10 times the median IC50 for each antiviral drug.. Median IC50 for each drug was as follows: ganciclovir, 5.2 microM; cidofovir, 11.0 microM; penciclovir, 13.9 microM; foscarnet, 232.9 microM; idoxuridine, 4.3 microM; and acyclovir, 57.9 microM. Obvious changes in morphologic characteristics, confluence, or viability of CRFK cells were not observed at concentrations up to and including 2 times the IC50 for each drug.. In vitro efficacy of idoxuridine and ganciclovir against FHV-1 was approximately equivalent and about twice that of cidofovir and penciclovir. Foscarnet appeared to be comparatively ineffective. Given the reasonable clinical efficacy of idoxuridine in cats infected with FHV-1, clinical trials of ganciclovir, cidofovir, and penciclovir or their prodrug forms appear to be warranted.

Topics: Acyclovir; Animals; Antiviral Agents; Cats; Cells, Cultured; Cidofovir; Cytosine; Dose-Response Relationship, Drug; Foscarnet; Ganciclovir; Guanine; Idoxuridine; In Vitro Techniques; Inhibitory Concentration 50; Organophosphonates; Organophosphorus Compounds; Varicellovirus; Virus Replication

Varicella-zoster virus (VZV) mutants were isolated under the pressure of different classes of antiviral compounds: (i) drugs that depend on the viral thymidine kinase (TK) for their activation, i.e. acyclovir (ACV), brivudin (BVDU), penciclovir (PCV) and sorivudine (BVaraU); (ii) drugs that are independent of the viral TK for their activation, i.e. 2-phosphonylmethoxyethyl (PME) derivatives of adenine (PMEA, adefovir) and 2,6-diaminopurine (PMEDAP); and (iii) drugs that do not require any metabolism to inhibit the viral DNA polymerase, i.e. foscarnet (PFA). Drug-resistant virus strains were obtained by serial passage of the OKA strain in human embryonic lung (HEL) fibroblasts and the different drug-resistant mutants were subsequently evaluated for their in vitro susceptibility to a broad range of antiviral drugs. Virus strains emerging under the pressure of ACV, BVDU and BVaraU were cross-resistant to all drugs that depend on the viral TK for activation, but remained susceptible to the acyclic nucleoside phosphonates (i.e. PMEA, PMEDAP and the 3-hydroxy-2-phosphonylmethoxypropyl derivatives of adenine (HPMPA) and cytosine (HPMPC, cidofovir)) and PFA. In contrast, the virus strains selected under pressure of PCV were resistant to PCV, ACV, PMEA and PFA; but not BVDU, BVaraU, GCV, HPMPC or HPMPA. Similar patterns of drug susceptibility were noted for the virus strains selected under the pressure of PMEA or PFA, pointing to an alteration in the viral DNA polymerase as basis for the resistant phenotype selected by PCV, as well as PMEA and PFA. In contrast, the resistant phenotype selected by ACV as well as BVDU and BVaraU may be attributed primarily to mutations in the viral TK gene. Our data thus indicate that ACV and PCV select in vitro for different drug-resistant VZV phenotypes; whether this is also the situation in vivo remains to be investigated.

Topics: 2-Aminopurine; Acyclovir; Adenine; Antiviral Agents; Arabinofuranosyluracil; Bromodeoxyuridine; Cidofovir; Cytosine; DNA-Directed DNA Polymerase; Drug Resistance, Multiple, Viral; Drug Resistance, Viral; Foscarnet; Guanine; Herpesvirus 3, Human; Humans; Microbial Sensitivity Tests; Mutation; Organophosphonates; Phenotype; Selection, Genetic; Thymidine Kinase; Viral Proteins

Platinum compounds containing an aromatic diimine (1,10-phenanthroline or 2,9-dimethyl-1,10-phenanthroline; phen and Me(2)phen, respectively) and antiviral guanosine-type ligands (acyclovir or penciclovir; acy and pen, respectively) have been synthesised. These compounds maintain the antiviral activity against Herpes Symplex Virus (HSV) and have greater efficacy than free acyclovir or penciclovir against Cytomegalovirus (CMV); in both cases the species with Me(2)phen are more active. The same complexes are effective against tumor cell proliferation which also results to be dependent upon the nature of the diimine ligand: all compounds containing Me(2)phen being more active than those containing phen. Although in vivo some complexes significantly reduce tumor cell proliferation, nevertheless, they do not appear to significantly affect the life time expectancy of the treated mice. The greater cytotoxicity of compounds with Me(2)phen may result from a higher reactivity towards cellular components, such as glutathione, which could cause release of the diimine, known to be highly cytotoxic.

Topics: Acyclovir; Animals; Antiviral Agents; Cell Line, Tumor; Cytomegalovirus; Guanine; Humans; Intercalating Agents; Mice; Molecular Structure; Phenanthrolines; Platinum Compounds; Simplexvirus

Topics: Acyclovir; Administration, Cutaneous; Antiviral Agents; Guanine; Herpes Labialis; Humans; Randomized Controlled Trials as Topic

The aim of this study was to develop models that allow serial, noninvasive imaging of human prostate cancer cells in immunodeficient mice using a dedicated small animal positron emission tomography scanner (microPET).. LNCaP tumor cells were stably transduced ex-vivo with the mutant herpes simplex virus type 1 thymidine kinase (HSV-sr39tk) PET reporter gene and green fluorescent protein (GFP). The stably transduced LNCaP cells were then enriched via fluorescent cell sorting and implanted into SCID mice. Beginning 2 weeks after tumor cell inoculation, mice were repeatedly scanned by microPET performed 1 hr after tail-vein injection of approximately 200 muCi Fluorine-18 labeled penciclovir ((18)F-FHBG). PET-images were correlated to tumor size, % injected dose (ID)/g tumor tissue, PSA levels, autoradiography, and histology.. Monitoring LNCaP xenografts using microPET and our reporter gene approaches is feasible. MicroPET was capable of detecting subcutaneous tumors as small as 3 mm in diameter (approximately 0.2% ID/g). The magnitude of (18)F-FHBG-uptake in PET-images correlated with the tumor volumes and the serum PSA levels. Other non-HSV1-TK-specific tracers were also studied. While (18)F-flurodeoxyglucose ((18)F-FDG) gave poor imaging results in LNCaP cells, (11)C-acetate gave satisfactory images.. We demonstrated the feasibility of monitoring prostate cancer xenografts in a mouse model using microPET and the HSV1-sr39tk PET reporter gene/(18)F-FHBG reporter probe system. Extension of this approach may allow repetitive imaging of tumor metastases.

Topics: Acyclovir; Animals; Disease Models, Animal; Flow Cytometry; Fluorine Radioisotopes; Genetic Vectors; Green Fluorescent Proteins; Guanine; Herpesvirus 1, Human; Humans; Luminescent Proteins; Male; Mice; Mice, SCID; Neoplasm Transplantation; Prostatic Neoplasms; Thymidine Kinase; Tomography, Emission-Computed; Transduction, Genetic; Transfection; Transplantation, Heterologous; Tumor Cells, Cultured

Hydrophilic drugs are poorly absorbed when applied topically, due to low partitioning through the lipid matrix of the stratum corneum. Cutaneous blood flow rapidly clears the absorbed drug, which may result in low tissue levels. This is of importance for topically applied drugs whose site of action is within the epidermis or dermis. Dermal drug levels can be measured using cutaneous microdialysis, which is a means of continuously sampling substances from the dermal extracellular fluid.. To measure the contribution of stratum corneum barrier and microvascular perfusion in determining dermal tissue levels of hydrophilic drugs (aciclovir and penciclovir) in vivo.. Studies were performed using microdialysis of the volar surface of the forearm of healthy volunteers (n = 55) over a 5-h collection period. Stratum corneum was removed by tape stripping, and barrier disruption quantified by measurement of transepidermal water loss (TEWL); dermal microvascular perfusion was modulated by inclusion of noradrenaline in the microdialysis perfusate.. With intact skin and normal cutaneous blood flow the concentration of penciclovir recovered was below assay threshold (0.05 ng x mL(-1). With noradrenaline-induced local vasoconstriction, the area under the curve of drug absorbed through normal skin (+/- SEM) was 13.3 +/- 2.9 ng mL(-1) h(0-5) for penciclovir and 27.6 +/- 10.6 ng mL(-1) h(0-5) for aciclovir. Removal of the stratum corneum (to glistening) by tape stripping increased penciclovir absorption by 1300-fold and aciclovir absorption by 440-fold, confirming the stratum corneum as the major barrier to hydrophilic drug absorption. Sequential barrier disruption by tape stripping gave a close correlation between penciclovir concentration absorbed per hour and barrier disruption measured by TEWL (r2 = 0.9283). There was a 15.6-fold difference in the recovery of penciclovir through barrier-deficient skin with and without cutaneous blood flow. There was no relationship between fibre depth and amount of drug dialysed, which suggests free movement of antiviral drug on reaching the aqueous environment of the dermis.. This study defines for the first time the relationship between the degree of mechanical barrier impairment and drug absorption at the same anatomical site in humans, and the role of blood flow in drug clearance in vivo.

Topics: Acyclovir; Administration, Topical; Adult; Aged; Antiviral Agents; Dermis; Epidermis; Female; Guanine; Humans; Male; Microdialysis; Middle Aged; Skin; Skin Absorption; Solubility; Water Loss, Insensible

Cell extraction and further sample preparation for nucleotide pool analysis using capillary electrophoresis was faster and simpler using volatile extraction solvents (e.g. organic solvents and de-ionized water) compared to the commonly applied acids dissolved in water (e.g. perchloric acid and trichloracetic acid). Temperature had to be controlled during the whole sample preparation process to prevent degradation, and extracts had to be cleaned from proteins and other large molecules prior to capillary electrophoretic analysis to improve reproducibility. Capillary electrophoresis using borate and cyclodextrins in the background electrolyte was used for determining 11 cellular nucleotides simultaneously. In order to optimize the assay, 0-100% acetonitrile, 0-100% ethanol, and 0-100% methanol in de-ionized water were applied to extract nucleotides from mouse lymphoma cells, and nucleotide yields, recovery, and reproducibility were compared. The assay met the commonly accepted validation limits for biological fluids, if 20-80% acetonitrile in water and 40-60% ethanol in water were used as extraction solvents.

Topics: Acyclovir; Electrophoresis, Capillary; Guanine; Nucleotides; Reproducibility of Results

Protein-protein interactions control essential steps in signal transduction pathways and other intracellular processes, and assembly of protein complexes modulates and responds to the regulatory events that exist in living animals. We have used microPET and fluorescence imaging to detect interactions between p53 tumor suppressor and large T antigen (TAg) of SV40 virus in a tetracycline-inducible two-hybrid system. To additionally validate this molecular imaging technique, we investigated whether expression of the reporter gene, comprised of a mutant thymidine kinase from herpes simplex virus 1 fused to green fluorescent protein could quantify relative differences in amounts of interacting hybrid proteins. In HeLa cells stably transfected with the reporter gene and interacting (p53-TAg) or noninteracting (p53 and polyoma virus coat protein) pairs of proteins, treatment with doxycycline produced time- and dose-dependent increases in expression of hybrid proteins. Proportional increases in amounts of reporter gene were produced only in cells expressing p53 and TAg. In mice bearing xenografts of these stably transfected HeLa cells, amounts of hybrid proteins were regulated with doxycycline. Both microPET imaging and biodistribution studies showed time- and dose-dependent increases in accumulation of the reporter substrate 9-(4-[(18)F]-fluoro-3-hydroxymethylbutyl)guanine only in p53-TAg tumors. Fluorescence microscopy of excised tumors also showed corresponding changes in expression of the fusion reporter gene in response to binding of p53 and TAg. These data demonstrate that the imaging two-hybrid system responds in a proportional fashion to increasing amounts of interacting proteins in vivo.

Topics: Acyclovir; Animals; Antigens, Viral, Tumor; Green Fluorescent Proteins; Guanine; HeLa Cells; Humans; Image Processing, Computer-Assisted; Luminescent Proteins; Mice; Mice, Nude; Microscopy, Fluorescence; Recombinant Fusion Proteins; Thymidine Kinase; Tomography, Emission-Computed; Transfection; Tritium; Tumor Suppressor Protein p53

A total of 21 clones of acyclovir (ACV)-resistant (ACV(r)) herpes simplex virus type 1 (HSV-1) and 23 clones of penciclovir (PCV)-resistant (PCV(r)) HSV-1, emerging during serial passages in the presence of ACV or PCV, were isolated under conditions excluding contamination of resistant mutants in the starting virus culture, and their mutations in the thymidine kinase (TK) and DNA polymerase (DNA Pol) genes were analyzed comparatively. Mutations in the TK genes from ACV(r) mutants consisted of 50% single nucleotide substitutions and 50% frameshift mutations, while the corresponding figures for the PCV(r) mutants were 4 and 96%, respectively (P < 0.001). Eight of the 21 ACV(r) clones, but none of the 23 PCV(r) clones, had mutations in DNA Pol. Only nucleotide substitution(s) could be detected in the DNA Pol gene, as the gene is essential for virus replication. Therefore, the results for the DNA Pol mutants are concordant with those for the TK mutants in that a single nucleotide substitution was commonly observed in the ACV(r), but not in the PCV(r), mutants. These results clearly point to differential mutation patterns between ACV(r) and PCV(r) HSV-1 clones.

Topics: Acyclovir; Antiviral Agents; DNA-Directed DNA Polymerase; DNA, Viral; Drug Resistance, Viral; Genotype; Guanine; Herpesvirus 1, Human; Humans; Mutation; Phenotype; Research Design; Thymidine Kinase; Tumor Cells, Cultured

Lamivudine [beta-L-(-)-2',3'-dideoxy-3'-thiacytidine] is a potent inhibitor of hepadnavirus replication and is used both to treat chronic hepatitis B virus (HBV) infections and to prevent reinfection of transplanted livers. Unfortunately, lamivudine-resistant HBV variants do arise during prolonged therapy, indicating a need for additional antiviral drugs. Replication-competent HBV constructs containing the reverse transcriptase domain L180M/M204V and M204I (rtL180M/M204V and rtM204I) mutations associated with lamivudine resistance were used to produce stable cell lines that express the resistant virus. These cell lines contain stable integrations of HBV sequences and produce both intracellular and extracellular virus. HBV produced by these cell lines was shown to have a marked decrease in sensitivity to lamivudine, with 450- and 3,000-fold shifts in the 50% inhibitory concentrations for the rtM204I and rtL180M/M204V viruses, respectively, compared to that for the wild-type virus. Drug assays indicated that the lamivudine-resistant virus exhibited reduced sensitivity to penciclovir [9-(4-hydroxy-3-hydroxymethyl-but-1-yl) guanine] but was still inhibited by the nucleoside analogues CDG (carbocyclic 2'-deoxyguanosine) and abacavir ([1S,4R]-4-[2-amino-6-(cyclopropylamino)-9H-purin-9-yl]-2-cyclopentene-1-methanol). Screening for antiviral compounds active against the lamivudine-resistant HBV can now be done with relative ease.

Topics: Acyclovir; Antiviral Agents; Base Sequence; Deoxyguanosine; Dideoxynucleosides; DNA, Viral; Drug Resistance, Viral; Guanine; Hepatitis B virus; Humans; Lamivudine; Microbial Sensitivity Tests; Molecular Sequence Data; Mutagenesis, Site-Directed; Transfection; Tumor Cells, Cultured; Virus Replication

Nucleoside analogues have been used in antiviral therapy and suicide cancer gene therapy. Therefore, it is of importance to compare their potential cytotoxic and genotoxic action. Using metabolically competent CHO cells expressing the thymidine kinase gene of herpes simplex virus type 1 (CHO-HSVtk cells) as a model system, the induction of DNA breaks was compared with the induction of structural chromosomal aberrations and apoptosis/necrosis after exposure to the anti-herpes nucleoside analogues aciclovir (ACV), ganciclovir (GCV) and penciclovir (PCV). After continuous treatment of CHO-HSVtk cells with the drugs, LD(10) in a colony-forming assay was 50, 0.5 and 1 microM for ACV, GCV and PCV, respectively, with GCV to be the most potent agent as determined at a given dose level. There was a remarkable difference in the activity of the agents to kill HSVtk expressing and non-expressing cells: the difference in cellular sensitivity of HSVtk(+) versus HSVtk(-) cells at LD(10) level was 7-fold for ACV, 60-fold for GCV and 400-fold for PCV. The drugs were shown to be strong inducers of apoptosis that was analysed as to concentration- and time-dependence; they induced to only very low extent necrosis. The agents were also highly potent in the induction of DNA single-strand breaks (SSBs) and double-strand breaks (DSBs) (as measured by single cell gel electrophoresis (SCGE)) and chromosomal aberrations. Although PCV induced DNA DSBs with a kinetics and frequency similar to that of GCV, it caused mostly condensation defects instead of "typical" structural chromosomal aberrations. For the drugs used, the frequency of apoptotic cells and the induction of abnormal mitoses appear to be related indicating genotoxic effects induced by the agents to be involved in cell killing due to apoptosis.

Topics: Acyclovir; Animals; Antiviral Agents; Apoptosis; CHO Cells; Chromosome Aberrations; Chromosomes; Colony-Forming Units Assay; Cricetinae; Cricetulus; DNA; DNA Damage; Enzyme Inhibitors; Ganciclovir; Guanine; Necrosis; Simplexvirus; Thymidine Kinase

The antiherpesvirus agent penciclovir (PCV) shares an identical activation pathway and a similar mode of action with acyclovir (ACV). However, since PCV represents a relatively recent treatment option, the clinical resistance profile to PCV is less well known. A susceptibility program was established to assess the resistance profile for serial herpes simplex virus isolates from immunocompetent patients with recurrent herpes labialis obtained throughout a 4-day period of treatment with topical PCV (1% cream) or a placebo. Two isolates (2 of 1,035 [0.19%]), representing 0.34% of the patients (2 of 585), were confirmed to be PCV-resistant (Pcv(r)) herpes simplex virus type 1 by a plaque reduction assay in MRC-5 cells. These two viruses were highly resistant to PCV (50% inhibitory concentrations [IC(50)s], >55 micro g/ml) and were isolated less than 17 h after the start of patient-initiated treatment. However, subsequent isolates on days 2 and 3 from these patients were completely susceptible to PCV (IC(50)s, <2.0 micro g/ml). Thus, it is not clear whether the resistance to PCV for these two early-treatment isolates was directly associated with the 17 h of PCV treatment; several possible explanations are discussed. In an analysis of the distribution of IC(50) differences between the first and last isolates, there were three patients with minor IC(50) increases in the PCV-treated population and one in the placebo-treated group, although statistically, only the latter was an outlier. No patients were found to have Pcv(r) virus at the end of acute treatment, regardless of treatment group. Overall, the prevalence of Pcv(r) was found to be similar to the 0.3% Acv(r) reported for immunocompetent, untreated populations.

Topics: Acyclovir; Antiviral Agents; Autoradiography; Drug Resistance, Viral; Frameshift Mutation; Guanine; Herpes Labialis; Herpesvirus 1, Human; Humans; Microbial Sensitivity Tests; Protein-Tyrosine Kinases; Recurrence; Viral Plaque Assay

In a general population survey in the United States, the prevalence of antiviral-agent-resistant herpes simplex virus was very low among more than 1,000 isolates from individuals with an episode of recurrent herpes labialis not treated with topical antiviral agents. Two isolates had borderline resistance to acyclovir (0.2%), and all were susceptible to penciclovir.

Topics: Acyclovir; Administration, Topical; Adult; Animals; Antiviral Agents; Cells, Cultured; Drug Resistance, Viral; Female; Guanine; Herpes Labialis; Herpesvirus 1, Human; Humans; Male; Population; Rabbits; Recurrence; United States

We developed a prostate cancer tumor model capable of being noninvasively imaged using positron emission tomography (PET) based on expression of the herpes simplex virus thymidine kinase (HSV1-tk) reporter gene.. The androgen independent, metastatic prostate cancer cell lines CL1 and CL1-GFP were stably transfected with the mutant HSV1-tk gene pcDNA3.1/pCMV-sr39tk, which has increased ability to phosphorylate penciclovir. The presence of the sr39tk gene product was analyzed by Western blot analysis and relative thymidine kinase enzyme activity was assessed by a functional thymidine kinase enzyme activity assay. Subcutaneous and orthotopic CL1 and CL1-SR39 tumor xenografts were established in SCID mice. The ability to image CL1-SR39 was assessed using fluorodeoxyglucose and F-penciclovir ( F-FHBG) micro-PET (a rodent PET scanner). To investigate the systemic distribution of intratumoral sr39tk injections established CL1 tumors were transiently injected with first generation adenoviral vectors carrying the sr39tk gene under control of the strong cytomegalovirus promoter Ad-CMV-HSV1-sr39tk and imaged using micro-PET.. Transfection of sr39tk into CL1 cells was successful. CL1-SR39 thymidine kinase enzyme activity was greater than twice the activity of the glioma cell line C6-SR39 control and above the threshold necessary for micro-PET detection. Fluorodeoxyglucose micro-PET in SCID mice was positive for CL1 and CL1-SR39 tumors. Selective micro-PET of subcutaneous CL1-SR39 tumors was done using F-FHBG. Micro-PET imaging after systemic and intratumoral injection of Ad-CMV-HSV1-sr39tk revealed significant systemic transgene leakage with significant hepatic expression of sr39TK protein.. Molecular based imaging of sr39tk transfected prostate cancer tumors and adenoviral delivered HSV1-tk suicide gene therapy based on the selective conversion and intracellular trapping of F-FHBG by sr39tk is feasible. Potential applications include noninvasive monitoring of the location, duration and intensity of gene constructs, which may contribute to the safety of clinical gene therapy protocols, and noninvasive imaging of the prostate cancer xenograft response to experimental therapy.

Topics: Acyclovir; Animals; Blotting, Western; Fluorodeoxyglucose F18; Genes, Reporter; Genetic Therapy; Genetic Vectors; Guanine; Herpesvirus 1, Human; Humans; Male; Mice; Mice, SCID; Neoplasm Transplantation; Prostatic Neoplasms; Radiopharmaceuticals; Thymidine Kinase; Tomography, Emission-Computed; Transfection; Tumor Cells, Cultured

To study the thermal stability, decomposition process and kinetics of such purine pharmaceuticals as aciclovir (Acv), penciclovir (Pcv), and their parent substance, guanine.. Using infrared technique, accelerating test method and thermogravimetry to investigate the thermal decomposition processes and using Coast-Redfern method, MKN method and Ozawa method to deal with the data to get kinetic functions.. The decomposition process and the formed products were derived, the kinetic model function was suggested by comparison of the kinetic parameters.. Pcv and Acv's degrading product for the first step is guanine. The sequences of their thermal stabilities is: Pcv > Acv. The two drugs' kinetic equation of thermal decomposition is expressed as: da/dt = Ae-Ea/RT2(1-alpha)3/2.

Topics: Acyclovir; Drug Stability; Guanine; Hot Temperature; Kinetics; Thermodynamics; Thermogravimetry

A number of in vitro assays are used to determine susceptibility of HSV to antiviral agents, but results from these in vitro assays do not necessarily correlate with treatment outcome.. A method with improved capability for identifying an isolate as acyclovir (ACV) or penciclovir (PCV) resistant when resistance is borderline could greatly improve the management of HSV disease.. A comparative evaluation of four in vitro assays, plaque reduction (PRA), DNA hybridization, plating efficiency (PEA) and plaque autoradiography (PAR) was performed to accurately identify and measure resistance of a TK-altered clinical HSV isolate (HSV-1 N4) from a patient who was non-responsive to ACV treatment. Two established criteria for the prediction of antiviral resistance, IC(50)> or =2.0 microg/ml or an IC(50) greater than 10x above a sensitive virus IC(50), as well as testing in human (MRC-5) and nonhuman (Vero and CV-1 monkey kidney) cell lines were evaluated.. The PRA and DNA hybridization assays accurately identified HSV-1 N4 as ACV(r) in human cells when using the 10x above sensitive virus IC(50) resistance criterion. Moreover, the PEA and PAR assays failed to classify HSV-1 N4 as drug resistant and indicate that these technologies alone are inadequate for identifying resistant virus.. The data presented herein indicate that the PRA and DNA hybridization assays most accurately identified an otherwise borderline-resistant isolate as drug resistant: (i) when a sensitive virus is used within each individual assay as a control, (ii) when ACV and PCV susceptibility is evaluated in human cells, and (iii) when the 10x above sensitive IC(50) criterion is used to classify a virus as drug-resistant. Testing of additional clinical samples is warranted to further confirm these findings.

Topics: Acyclovir; Antiviral Agents; Autoradiography; Drug Resistance, Viral; Guanine; Microbial Sensitivity Tests; Nucleic Acid Hybridization; Simplexvirus; Thymidine Kinase; Viral Plaque Assay

Topics: 2-Aminopurine; Acyclovir; Administration, Oral; Administration, Topical; Amantadine; Animals; Antiviral Agents; Cidofovir; Cytosine; Famciclovir; Foscarnet; Guanine; Herpesviridae Infections; Humans; Influenza, Human; Injections, Intravenous; Lamivudine; Organophosphonates; Organophosphorus Compounds; Rats; Ribavirin; Rimantadine; Thionucleotides; Trifluridine; Valacyclovir; Valine

The commonly used antiviral drugs acyclovir (ACV) and penciclovir (PCV) possess similarly potent antiviral activities in vivo against herpes simplex virus (HSV). Assay methods for sensitivity to ACV are not necessarily transferable to PCV, even though the two drugs have similar in vivo potencies and mechanisms of action. We determined by plaque reduction assay the relative activities of ACV and PCV against five laboratory-adapted strains of HSV types 1 and 2 (including sensitive and resistant strains) in seven human cell lines and one nonhuman primate cell line. Seven characteristics were used to evaluate the cell lines. All cell lines were similar in their plating efficiencies and abilities to discriminate between sensitive and resistant HSV isolates. Vero and MRC-5 cells yielded the most discordant 50% inhibitory concentrations (IC50s) for the two HSV types, while Vero and WI-38 VA-13 cells yielded large differences in the IC50s of ACV and PCV. The limited life spans and poor plaque morphologies of the fibroblast lines were undesirable characteristics. Among the transformed cell lines producing well-defined plaques, A549 cells provided the best concordance between IC50s for the two HSV types and two antiherpes drugs. Comparison experiments with a yield reduction format indicated that the use of assays of this type might allow some of the cell-specific properties observed in plaque reduction assays to be avoided.

Topics: Acyclovir; Animals; Antiviral Agents; Cell Division; Cell Line; Genotype; Guanine; Humans; Phenotype; Phosphorylation; Simplexvirus; Viral Plaque Assay

Levels of bystander death occurring in herpes simplex virus type 1 (HSV-1)-infected mouse brain stems were studied, as well as the extent to which bystander death is influenced by guanosine nucleoside analogue treatment. Consecutive sections from brain stems of HSV-1-infected mice were stained alternately for (i) viral infection and (ii) cell death (TUNEL assay). Virus antigen was detectable in brain stems on day 3 of infection, while TUNEL staining was comparatively lower. An increase in the extent of TUNEL staining was observed on day 4 of infection. Despite this increase, however, the ratio of TUNEL-stained to infection marker-stained tissue still indicated that the amount of TUNEL staining remained lower than infection staining at this time point. On days 5 and 6 of infection, TUNEL staining continued to increase and the TUNEL/infection marker ratio switched on day 6 in favour of excess TUNEL staining, which was observed in and around the foci of infection, suggesting bystander death. The excess TUNEL staining on day 6 of infection was further increased on treatment with antivirals. The significance and implications of these results are discussed with respect to the nature and mechanism of action of the TUNEL assay, dynamics of primary HSV-1 infection, immunological influences and potential effects of antiviral treatment. The potential problems of the TUNEL assay are considered in the context of viral infection and the TUNEL assay, in combination with infection marker staining, may potentially provide a model system for quantitative analysis of true bystander death during HSV infection in vivo.

Topics: 2-Aminopurine; Acyclovir; Animals; Antiviral Agents; Apoptosis; Brain Stem; Disease Models, Animal; DNA Fragmentation; Famciclovir; Female; Ganciclovir; Guanine; Herpes Simplex; Herpesvirus 1, Human; Humans; In Situ Nick-End Labeling; Mice; Mice, Inbred BALB C; Valacyclovir; Valine

The efficacies of ganciclovir (GCV), penciclovir (PCV) and acyclovir (ACV) in inducing cell death in the herpes simplex virus thymidine kinase (HSVTK) system were compared. HSVTK-transformed baby hamster kidney cells treated with GCV, PCV or ACV were monitored for growth by viable count, and for death by TUNEL assay, propidium iodide staining, detection of phosphatidyl serine translocation and detection of DNA laddering. All compounds delayed growth or reduced viability of HSVTK-transformed cells. Drug treatment reduced levels of cyclin B1 message (which normally peaks in G2/M-phase of the cell cycle) and induced a four- to fivefold upregulation of GADD45 message. Treatment with GCV or PCV induced rapid accumulation of cells in S-phase and apoptotic death. Treatment with ACV, however, was associated with sustained S-phase arrest. GCV (and to a lesser extent PCV) increased phosphatidyl serine translocation, induced positive TUNEL results with alterations in cell morphology, caused marked propidium iodide staining and induced DNA laddering. By contrast, up to 7 days' exposure to ACV did not induce DNA laddering, with very little TUNEL staining. ACV treatment had little effect on phosphatidyl serine translocation and propidium iodide staining was markedly reduced compared with treatment with the other compounds. Thus, by all criteria, GCV was the most potent inducer of cell death. The current theories regarding apoptosis or necrosis as the preferred form of cell death in prodrug gene therapy are considered and the suitability of PCV or ACV as potential alternatives to GCV in the HSVTK system is discussed.

Topics: Acyclovir; Animals; Apoptosis; Cell Cycle; Cell Line, Transformed; Cell Size; Cell Survival; Cricetinae; Flow Cytometry; Ganciclovir; Genetic Therapy; Guanine; Herpesvirus 1, Human; Humans; Kidney; Reverse Transcriptase Polymerase Chain Reaction; Thymidine Kinase

Penciclovir (PCV), an antiherpesvirus agent in the same class as acyclovir (ACV), is phosphorylated in herpes simplex virus (HSV)-infected cells by the viral thymidine kinase (TK). Resistance to ACV has been mapped to mutations within either the TK or the DNA polymerase gene. An identical activation pathway, the similarity in mode of action, and the invariant cross-resistance of TK-negative mutants argue that the mechanisms of resistance to PCV and ACV are likely to be analogous. A total of 48 HSV type 1 (HSV-1) and HSV-2 isolates were selected after passage in the presence of increasing concentrations of PCV or ACV in MRC-5 cells. Phenotypic analysis suggested these isolates were deficient in TK activity. Moreover, sequencing of the TK genes from ACV-selected mutants identified two homopolymeric G-C nucleotide stretches as putative hot spots, thereby confirming previous reports examining Acv(r) clinical isolates. Surprisingly, mutations identified in PCV-selected mutants were generally not in these regions but distributed throughout the TK gene and at similar frequencies of occurrence within A-T or G-C nucleotides, regardless of virus type. Furthermore, HSV-1 isolates selected in the presence of ACV commonly included frameshift mutations, while PCV-selected HSV-1 mutants contained mostly nonconservative amino acid changes. Data from this panel of laboratory isolates show that Pcv(r) mutants share cross-resistance and only limited sequence similarity with HSV mutants identified following ACV selection. Subtle differences between PCV and ACV in the interaction with viral TK or polymerase may account for the different spectra of genotypes observed for the two sets of mutants.

Topics: Acyclovir; Animals; Antiviral Agents; Autoradiography; Cell Line; DNA, Viral; Drug Resistance, Microbial; Guanine; Herpesvirus 1, Human; Herpesvirus 2, Human; Humans; Mutation; Sequence Analysis, DNA; Thymidine Kinase; Viral Plaque Assay

Topics: Acyclovir; Adenoviridae; Animals; Antiviral Agents; Gene Expression; Genes, Reporter; Genetic Vectors; Guanine; Herpesvirus 1, Human; Humans; Thymidine Kinase; Tomography, Emission-Computed; Transfection

We have synthesized and evaluated 8-[18F]fluoropenciclovir (FPCV) and compared it with 8-[18F]fluoroganciclovir (FGCV) for monitoring the expression of herpes simplex virus type 1 thymidine kinase (HSV1 -tk) reporter gene in cell culture and in vivo.. C6 rat glioma cells stably transfected with HSV1-tk (C6-stb-tk+) and control C6 cells were evaluated for their ability to accumulate FGCV versus FPCV. For in vivo studies, 15 mice were injected by tail vein with increasing levels of an adenoviral vector carrying HSV1-tk. Forty-eight hours later the mice were injected with FPCV and killed 3 h later. The percentage injected dose per gram (%ID/g) liver was then determined. Two additional mice were studied by microPET and autoradiography using FPCV to image adenoviral-mediated hepatic HSV1-tk reporter gene expression. A tumor-bearing mouse (C6 control and C6-stb-tk+) was imaged with FDG, FGCV, and FPCV. Two mice carrying tumors expressing two different reporter genes, HSV1-tk and dopamine type 2 receptor (D2R), were also imaged by microPET using FPCV (day 1) and 3-(2'-[18F]fluoroethyl)spiperone (FESP) (day 2).. FPCV shows a significantly greater accumulation in C6-stb-tk+ cells than does FGCV (P < 0.05). Over identical ranges of adenoviral administration, mouse liver shows a higher %ID/g liver for FPCV (0%-9%) compared with our previously reported results with FGCV (0%-3%). In C6 control and C6-stb-tk+ tumor-bearing mice, FPCV has a greater accumulation than does FGCV for equal levels of HSV1-tk gene expression. In mice carrying tumors expressing either HSV1-tk or D2R reporter genes, there is a corresponding retention of FPCV and FESP, respectively.. These results indicate that FPCV is a better reporter probe than is FGCV for imaging lower levels of HSV1 -tk gene expression in vivo. The results also reveal the ability to monitor the expression of two distinct reporter genes in the same animal using reporter probes specific for each gene.

Topics: Acyclovir; Adenoviridae; Animals; Antiviral Agents; Cells, Cultured; Fluorine Radioisotopes; Gene Expression; Genes, Reporter; Genetic Vectors; Guanine; Herpesvirus 1, Human; Mice; Rats; Receptors, Dopamine D2; Thymidine Kinase; Tomography, Emission-Computed

Topics: Acyclovir; Administration, Topical; Antiviral Agents; Guanine; Herpes Labialis; Humans; Recurrence

The presence of Epstein-Barr virus (EBV) in the tumor cells of some EBV-associated malignancies may facilitate selective killing of these tumor cells. We show that treatment of an EBV(+) Burkitt's lymphoma cell line with 5-azacytidine led to a dose-dependent induction of EBV lytic antigen expression, including expression of the viral thymidine kinase (TK) and phosphotransferase (PT). Azacytidine treatment for 24 h modestly sensitized the cell line to all nucleosides tested. To better characterize EBV TK with regard to various nucleoside analogues, we expressed EBV TK in stable cell clones. Two EBV TK-expressing clones were moderately sensitive to high doses of acyclovir and penciclovir (PCV) (62.5 to 500 microM) and to lower doses of ganciclovir (GCV) and bromovinyldeoxyuridine (BVdU) (10 to 100 microM) compared to a control clone and were shown to phosphorylate GCV. Similar experiments in a transient overexpression system showed more killing of cells transfected with the EBV TK expression vector than of cells transfected with the control mutant vector (50 microM GCV for 4 days). A putative PT was also studied in the transient transfection system and appeared similar to the TK in phosphorylating GCV and conferring sensitivity to GCV, but not in BVdU- or PCV-mediated cell killing. Induction of EBV kinases in combination with agents such as GCV merits further evaluation as an alternative strategy to gene therapy for selective killing of EBV-infected cells.

Topics: Acyclovir; Antigens, Viral; Antimetabolites, Antineoplastic; Antiviral Agents; Azacitidine; Cell Division; Dose-Response Relationship, Drug; Drug Interactions; Enzyme Induction; Ganciclovir; Guanine; Herpesvirus 4, Human; Humans; Thymidine Kinase; Tumor Cells, Cultured

2-Amino-9-(3-acetoxymethyl-4-isopropoxycarbonyloxybut-1-yl)- purine (SK1899) was tested as an oral prodrug for penciclovir. SK1899 was administered orally to rats and dogs at doses up to 2 and 0.68 mmol/kg, respectively. SK1899 was well absorbed, and the major metabolites detected in plasma and urine were penciclovir, the active antiviral compound, and 6-deoxypenciclovir (M4) in both species. In rats, SK1899 was rapidly and extensively metabolized to penciclovir, which reached the peak plasma concentration (C(max)) of 39.5 microM at 0.5 h after 0.2-mmol/kg dosing. The area under the plasma concentration-time curve (AUC) for penciclovir was 57.5 microM x h. After an oral dose of 0.034 mmol/kg to dogs, extensive conversion of SK1899 to penciclovir also occurred with slower rate of formation of penciclovir from M4 than in rats. The mean C(max) and AUC for penciclovir were 4.5 microM at 2.7 h and 28.2 microM x h, respectively. The 0- to 24-h urinary recovery of penciclovir represented 36.1 and 36.3% of dose to rats and dogs, respectively. Radioactivity was found in fetuses following an oral administration of [(14)C]SK1899 to pregnant rats, but no significant accumulation was observed. Although substantial milk transfer of [(14)C]SK1899 occurred in rats, the radioactivity in milk was rapidly cleared. The values of C(max), AUC, and urinary recovery of penciclovir after dosing with SK1899 to rats and dogs were similar or slightly higher than those from famciclovir. These data indicate that introduction of an isopropoxy carbonate group into one of the two hydroxyl groups of M4 did not significantly alter the oral bioavailability of penciclovir compared with famciclovir.

Topics: Acyclovir; Animals; Antiviral Agents; Area Under Curve; Dogs; Drug Evaluation, Preclinical; Female; Guanine; Male; Milk; Pregnancy; Prodrugs; Purines; Rats; Rats, Sprague-Dawley

Topics: Acyclovir; Antiviral Agents; Fatty Alcohols; Guanine; Herpes Labialis; Humans; Recurrence; Simplexvirus; Stomatitis, Herpetic; Virulence; Virus Activation; Virus Shedding

Recent studies suggest reductions in establishment of herpes simplex virus, type 1 (HSV-1) latency using the nucleoside analog penciclovir compared with acyclovir in the murine model. These observations raise the possibility that the new analogs may have novel activities that directly interfere with the establishment of the latent infection, suggesting a mechanism other than simply blocking the productive infection. To determine if penciclovir has a direct action on the establishment of latency, we compared the effects of penciclovir versus acyclovir in an in vitro model of HSV-1 latency in rat dorsal root ganglia neurons in culture. In neurons in culture, both penciclovir and acyclovir were highly effective in blocking the productive infection. However, neither penciclovir nor acyclovir blocked establishment of latency as demonstrated by similar percentages of neurons expressing the latency-associated transcript (LAT). Following removal of the respective nucleoside analog, latency was maintained until reactivation was induced by nerve growth factor deprivation. Similar virus titers were recovered after induction of reactivation of latent infections, which were established in the presence of either penciclovir or acyclovir. These results indicate that neither penciclovir nor acyclovir treatment directly prevents the establishment of latent HSV-1 infections in primary sensory neurons in culture.

Topics: Acyclovir; Animals; Antiviral Agents; Cells, Cultured; Ganglia, Spinal; Gene Expression Regulation, Viral; Guanine; Herpes Simplex; Herpesvirus 1, Human; Humans; In Situ Hybridization; Neurons, Afferent; Rats; Reverse Transcriptase Inhibitors; Time Factors; Transcription, Genetic; Viral Plaque Assay; Virus Activation; Virus Latency

There are 3 new topical treatments for herpes labialis that have either been approved by the US Food and Drug Administration (penciclovir cream [Denavir] and n-docosanol cream [Abreva]) or recently undergone extensive clinical evaluation (acyclovir cream). The relative efficacy of these products is unknown.. To compare the efficacy of penciclovir cream, acyclovir cream, n-docosanol cream, and acyclovir ointment in an experimental animal model of cutaneous herpes simplex virus type 1 (HSV-1) disease.. The backs of guinea pigs were infected with HSV-1 using a vaccination instrument. Active treatments and corresponding vehicle controls were applied for 3 to 5 days beginning 24 hours after inoculation.. After completion of treatment, the animals were killed and the severity of the infection assessed from the number of lesions, the total lesion area, and the lesion virus titer.. Penciclovir cream effected modest reductions in lesion number (19%), area (38%), and virus titer (88%) compared with its vehicle control, and each of these differences was significantly greater (P<.05) than the reductions effected by acyclovir ointment (0%, 21%, and 75%, respectively). The acyclovir cream effect (reductions of 4%, 28%, and 77%, respectively) was less than that of penciclovir cream, and this difference was confirmed by 2 additional head-to-head experiments. Two experiments with n-docosanol cream failed to show statistically significant differences by any parameter between n-docasonol cream and vehicle control-treated sites or between n-docosanol and untreated infection sites.. In this model, the efficacy of penciclovir cream was greater than acyclovir cream, acyclovir cream was greater than or equal to acyclovir ointment, and acyclovir ointment was greater than n-docosanol cream. Since our model was designed to evaluate compounds that function primarily through antiviral activity, the negative findings with n-docosanol in these studies do not exclude that it might work clinically through other mechanisms.

Topics: Acyclovir; Administration, Topical; Animals; Disease Models, Animal; Fatty Alcohols; Female; Guanine; Guinea Pigs; Herpes Labialis; Herpesvirus 1, Human; Humans; Treatment Outcome

Topics: Acyclovir; Administration, Topical; Animals; Antiviral Agents; Disease Models, Animal; Fatty Alcohols; Guanine; Guinea Pigs; Herpes Labialis; Humans; Ointments; Treatment Outcome

The gene for herpes simplex virus thymidine kinase (HSV-tk) is widely used as a suicide gene in experimental gene therapy of cancer. 9-(4-Fluoro-3-hydroxymethylbutyl)guanine (FHBG) is an antiviral nucleoside analog that is rapidly phosphorylated by viral thymidine kinase but is a poor substrate for mammalian thymidine kinase. Recently, FHBG labeled in the 4-fluoro position with (18)F has shown promise relative to other similar compounds for imaging in vivo expression of HSV-tk using PET. In this study, we evaluated the uptake of [(18)F]FHBG in vitro and in vivo using transduced and wild-type human colon cancer cells (HT-29). We also imaged [(18)F]FHBG and measured the radioactivity concentrations of circulating [(18)F]FHBG and its metabolites in monkeys.. Sterile, pyrogen-free [(18)F]FHBG was produced routinely in good yields. Cells were transduced with the retroviral vector G1Tk1SvNa containing HSV-tk gene. In vitro uptake studies were performed by incubating cells with [(18)F]FHBG at 37 degrees C for 1 and 5 h. Biodistribution studies were performed at 2 and 5 h after injection in nude mice bearing tumors grown from wild-type or transduced cells. Sequential, whole-body PET scans of cynomolgus monkeys were obtained over a period of >2 h after intravenous injection of [(18)F]FHBG. Arterial plasma samples obtained from monkeys 15-120 min after intravenous injection were subjected to acid extraction, and the acid-soluble fractions were analyzed by high-performance liquid chromatography.. In vitro studies showed 31 and 71 (P < 0.001) times higher uptake of the probe at 1 and 5 h, respectively, in transduced cells compared with nontransduced cells. In vivo studies in mice showed that tumor uptake of the radiotracer was 4-fold (P < 0.05) and 13-fold (P < 0.001) higher at 2 and 5 h, respectively, in tumors grown from transduced cells compared with control cells. Transduced tumor-to-normal tissue ratios ranged from 2 to 25 at 2 h and from 2 to 22 at 5 h. Recirculating labeled metabolites had only a minor effect on the biodistribution of radiolabel from [(18)F]FHBG in monkeys.. These results indicate that [(18)F]FHBG may yield high-contrast PET images of HSV-tk expression in tumors and, therefore, it is a very promising radiotracer for monitoring of gene therapy of cancer with PET.

Topics: Acyclovir; Animals; Antiviral Agents; Chromatography, High Pressure Liquid; Gene Expression Regulation, Enzymologic; Genetic Therapy; Guanine; HT29 Cells; Humans; Macaca fascicularis; Male; Mice; Mice, Nude; Neoplasm Transplantation; Radiopharmaceuticals; Simplexvirus; Thymidine Kinase; Tissue Distribution

Acyclovir (ACV) resistant herpes simplex virus (HSV) isolates can be readily selected in animal infection models receiving suboptimal ACV treatment, however no comparative studies of the emergence of resistance following suboptimal treatment with valacyclovir (VCV) or famciclovir (FCV), the prodrugs of acyclovir and penciclovir, respectively, have been reported.. Mice (n = 30) were infected with HSV type 1 or 2 in the ear pinnae and administered oral prodrugs at one fifth a dose previously shown to be effective. To select and amplify drug-resistant HSV, a total of seven consecutive in vivo passages with suboptimal treatment were performed for each virus sample and progeny virus from each passage was characterized by the plaque reduction (PRA) and plating efficiency assays (PEA).. No drug-resistant HSV-2 and only a single drug-resistant HSV-1 variant were identified. Virus recovered from the first three sequential passages of this HSV-1 sample was susceptible by PRA, although the proportion of resistant virus recovered gradually increased upon passage. The resistant HSV-1 phenotype was confirmed by PRA after four sequential passages in mice. Unexpectedly, this in vivo-selected drug-resistant HSV-1 failed to yield an infection completely refractory to treatment in subsequent passages.. Sub-optimal therapy of immunocompetent mice with either VCV or FCV did not readily select for HSV-mutants resistant to either ACV or PCV, suggesting that selection of resistance with either prodrug remains difficult using this system. Futhermore, this study suggests that the PEA may represent a useful adjunct to the PRA for monitoring alterations in the proportion of drug-resistant virus even when no change in IC50 is apparent.

Topics: Acyclovir; Administration, Oral; Animals; Antiviral Agents; Disease Models, Animal; Drug Resistance, Viral; Female; Guanine; Herpes Simplex; Mice; Mice, Inbred BALB C; Microbial Sensitivity Tests; Prodrugs; Simplexvirus; Viral Load

We studied the genotoxic and apoptosis-inducing properties of ganciclovir (GCV) and penciclovir (PCV) using Chinese hamster ovary cells stably transfected with the thymidine kinase (tk) gene of herpes simplex virus-1 (HSV-1). Cells expressing HSVtk were 300 and 100 times more sensitive than their isogenic HSVtk- counterparts to the cytotoxic effects of GCV and PCV, respectively. Using radiolabeled drugs, GCV was found to be incorporated into the genomic DNA much more effectively than PCV. GCV was highly potent in inducing chromosomal aberrations compared with PCV, which provoked less sister chromatid exchanges and chromosomal changes using equimolar or equitoxic doses. For both agents, apoptosis was shown to be the major route of cell killing. Time course experiments revealed that neither genotoxicity nor apoptosis were induced within the cell cycle exposed to the drug; they are late events provoked in the following cell cycle(s). This indicates that the incorporation/exposure step of GCV or PCV into DNA is not decisive for triggering genotoxicity and apoptosis, but that events occurring subsequently, presumably during replication of a DNA containing the nucleotide analogs, are of major importance. Because PCV, unlike GCV, induced highly effectively apoptosis without exerting much genotoxicity, the use of PCV as a relatively safe alternative drug for suicide gene therapy of malignant diseases is recommended.

Topics: Acyclovir; Animals; Apoptosis; Cell Cycle; CHO Cells; Cricetinae; DNA; DNA Replication; Ganciclovir; Genetic Therapy; Guanine; Herpesvirus 1, Human; Mutagenicity Tests; Necrosis; Sister Chromatid Exchange; Thymidine Kinase; Transfection

Penciclovir (9-[2-hydroxy-1-(hydroxymethyl)-ethoxymethyl]guanine [PCV]), lamivudine ([-]-beta-L-2',3'-dideoxy-3'-thiacytidine [3TC]), and adefovir (9-[2-phosphonylmethoxyethyl]-adenine [PMEA]) are potent inhibitors of hepatitis B virus (HBV) replication. Lamivudine has recently received approval for clinical use against chronic human HBV infection, and both PCV and PMEA have undergone clinical trials against HBV in their respective prodrug forms (famciclovir and adefovir dipivoxil [bis-(POM)-PMEA]). Since multidrug combinations are likely to be used to control HBV infection, investigation of potential interactions between PCV, 3TC, and PMEA is important. Primary duck hepatocyte cultures which were either acutely or congenitally infected with the duck hepatitis B virus (DHBV) were used to investigate in vitro interactions between PCV, 3TC, and PMEA. Here we show that the anti-DHBV effects of all the combinations containing PCV, 3TC, and PMEA are greater than that of each of the individual components and that their combined activities are approximately additive or synergistic. These results may underestimate the potential in vivo usefulness of PMEA-containing combinations, since there is evidence that PMEA has immunomodulatory activity and, at least in the duck model of chronic HBV infection, is capable of inhibiting DHBV replication in cells other than hepatocytes, the latter being unaffected by treatment with either PCV or 3TC. Further investigation of the antiviral activities of these drug combinations is therefore required, particularly since each of the component drugs is already in clinical use.

Topics: Acyclovir; Adenine; Animals; Antiviral Agents; Cells, Cultured; Drug Interactions; Drug Therapy, Combination; Ducks; Guanine; Hepadnaviridae Infections; Hepatitis B Virus, Duck; Humans; Lamivudine; Liver; Organophosphonates; Virus Replication

The unique clinical and pathological findings in nine Asian (Elephas maximus) and two African (Loxodonta africana) elephants from North American Zoos with a highly fatal disease caused by novel endotheliotropic herpesviruses are described. Identification of the viruses by molecular techniques and some epidemiological aspects of the disease were previously reported. Consensus primer polymerase chain reaction (PCR) combined with sequencing yielded molecular evidence that confirmed the presence of two novel but related herpesviruses associated with the disease, one in Asian elephants and the second in African elephants. Disease onset was acute, with lethargy, edema of the head and thoracic limbs, oral ulceration and cyanosis of the tongue followed by death of most animals in 1 to 7 days. Pertinent laboratory findings in two of three clinically evaluated animals included lymphocytopenia and thrombocytopenia. Two affected young Asian elephants recovered after a 3 to 4 wk course of therapy with the anti-herpesvirus drug famciclovir. Necropsy findings in the fatal cases included pericardial effusion and extensive petechial hemorrhages in the heart and throughout the peritoneal cavity, hepatomegaly, cyanosis of the tongue, intestinal hemorrhage, and ulceration. Histologically, there were extensive microhemorrhages and edema throughout the myocardium and mild, subacute myocarditis. Similar hemorrhagic lesions with inflammation were evident in the tongue, liver, and large intestine. Lesions in these target organs were accompanied by amphophilic to basophilic intranuclear viral inclusion bodies in capillary endothelial cells. Transmission electron microscopy of the endothelial inclusion bodies revealed 80 to 92 nm diameter viral capsids consistent with herpesvirus morphology. The short course of the herpesvirus infections, with sudden deaths in all but the two surviving elephants, was ascribed to acute cardiac failure attributed to herpesvirus-induced capillary injury with extensive myocardial hemorrhage and edema.

Topics: 2-Aminopurine; Acyclovir; Animals; Animals, Zoo; Antiviral Agents; DNA, Viral; Elephants; Endothelium, Vascular; Famciclovir; Female; Guanine; Herpesviridae; Herpesviridae Infections; Liver; Lung; Male; Myocardium; North America; Polymerase Chain Reaction; Prodrugs; Retrospective Studies; Tongue

In this work, we investigated the anti-hepatitis B virus (HBV) activity of lamivudine, adefovir, tenofovir, penciclovir and lobucavir after short-term (i.e. 24 or 48 h) or continuous (9 days) exposure of the HBV-containing cell line, HepG2 2.2.15, to these drugs. Lamivudine maintained significant anti-HBV activity when added for only 24 or 48 h to the cell cultures compared to when the drug was present for the whole period (9 days) on the cells, i.e. 50% effective concentration (EC50) values for the inhibition of HBV DNA synthesis were 0.07 +/- 0.02 microgram ml-1 after 24 h of incubation, 0.02 +/- 0.01 microgram ml(-1) after 48 h of incubation and 0.0016 +/- 0.001 microgram ml(-1) after 9 days of incubation. Similarly, the nucleoside phosphonate analogues, adefovir and tenofovir, retained significant anti-HBV activity when added for only a short period of time to the cells. The EC50 values were 12 +/- 1 microgram ml(-1) (24 h) and 1.0 +/- 0.2 microgram ml(-1) (48 h) vs 0.003 +/- 0.001 microgram ml(-1) (9 days) for adefovir, and 6.5 +/- 1.1 microgram ml(-1) (24 h) and 0.8 +/- 0.1 microgram ml(-1) (48 h) vs 0.03 +/- 0.02 microgram ml(-1) (9 days) for tenofovir. In contrast, penciclovir and lobucavir lost most of their anti-viral activity when present on the cells for 48 h or less.

Topics: Acyclovir; Adenine; Antiviral Agents; Carcinoma, Hepatocellular; DNA, Viral; Guanine; Hepatitis B virus; Lamivudine; Organophosphonates; Organophosphorus Compounds; Tenofovir; Tumor Cells, Cultured

The three anti-herpes nucleoside analogues ganciclovir, penciclovir and aciclovir were investigated as to their recombinogenic [sister chromatid exchange (SCE) inducing] and clastogenic activity in CHO cells expressing the thymidine kinase gene of HSV-1, which is a precondition of therapeutic activity of these drugs. The compounds were applied for the duration of one cell cycle and cytogenetic end-points were measured between 0 and 42 h after exposure. Although the nucleoside analogues are quite similar with respect to chemical structure, they differ basically in their genotoxic potency, aberration types induced as well as the time course of chromosomal damage. Aciclovir induced SCEs and chromosomal aberrations immediately after exposure but only in a concentration range much higher than that reached in blood plasma during anti-herpes therapy. The direct genotoxic activity is explained by the obligate chain terminating property of aciclovir upon incorporation into genomic DNA. On the other hand, genotoxic damage caused by ganciclovir and penciclovir is of the delayed type requiring at least one post-exposure cell cycle for its expression. Unlike aciclovir, ganciclovir is an extremely potent inducer of SCEs and chromosome breaks and translocations at concentrations far below those impairing the proliferative activity and triggering apoptosis of the target cells (as shown by our previous investigation). Penciclovir is essentially devoid of genotoxic activity. It induces SCEs only at cytotoxic/apoptotic concentrations, is only weakly clastogenic and induces premature chromosome condensation which appears to result from uncoupling of karyokinesis and cytokinesis. The genotoxic activity of ganciclovir is explained as due to repair processes triggered in the second post-exposure replication cycle at the sites of nucleoside analogue incorporation into genomic DNA. The findings have considerable implications with respect to the use of ganciclovir or other antiviral drugs in suicide gene therapy of malignant diseases.

Topics: Acyclovir; Animals; Antiviral Agents; CHO Cells; Chromosomes; Cricetinae; Dose-Response Relationship, Drug; Ganciclovir; Guanine; Herpesvirus 1, Human; Mutagens; Sister Chromatid Exchange; Thymidine Kinase; Time Factors

Several nucleoside analogues (penciclovir, lobucavir, dioxalane guanine [DXG], 1-beta-2,6-diaminopurine dioxalane [DAPD], L-FMAU, lamivudine) and acyclic nucleoside phosphonate analogues (adefovir, tenofovir) that are in clinical use, in clinical trials or under preclinical development for the treatment of hepatitis B virus (HBV) infections, were evaluated for their inhibitory effect on the replication of a la- mivudine-resistant HBV variant containing the methionine --> valine substitution (M550V) in the polymerase nucleoside-binding domain. The antiviral activity was determined in the tetracycline-responsive HepAD38 and HepAD79 cells, which are stably transfected with either a cDNA copy of the wild-type pregenomic RNA or with cDNA containing the M550V mutation. As expected, lamivudine was much less ( approximately 200-fold) effective at inhibiting replication of the M550V mutant virus than the wild-type virus. In contrast, adefovir, tenofovir, lobucavir, L-FMAU, DXG and DAPD proved almost equally effective against both viruses. A second objective of this study was to directly compare the antiviral potency of the anti-HBV agents in HepG2 2.2.15 cells (which are routinely used for anti-HBV drug-screening purposes) with that in HepAD38 cells. HepAD38 cells produce much larger quantities of HBV than HepG2 2.2.15 cells, and thus allow drug screening in a multiwell plate format. All compounds were found to be almost equally effective at inhibiting HBV replication in HepAD38 cells (as in HepG2 2.2.15 cells), except for penciclovir, which was clearly less effective in HepAD38 cells.

Topics: Acyclovir; Adenine; Antiviral Agents; Arabinofuranosylcytosine Triphosphate; Cell Line; Dioxolanes; DNA-Directed DNA Polymerase; DNA, Viral; Guanine; Hepatitis B virus; Humans; Organophosphonates; Organophosphorus Compounds; Purine Nucleosides; Tenofovir; Virus Replication

Recent studies have implicated bile duct epithelial cells (BDEC) as a reservoir of hepatitis B virus (HBV) infection that may be particularly important in the development of post-liver transplant recurrence of hepatitis B. The aim of this study was to compare the effects of antiviral therapy on duck HBV (DHBV) expression in hepatocytes and BDEC and to determine if this was affected by biliary hyperplasia.. Ducklings congenitally infected with DHBV received penciclovir (10 mg/kg per day) treatment from 9 days of age. In order to mimic the biliary hyperplasia that often accompanies severe post-liver transplant HBV recurrence, half the animals underwent bile duct ligation. Duck HBV-DNA in serum was measured at day 1, and serum and liver DHBV-DNA were determined when the animals were killed on day 17. Intrahepatic expression of viral preS1 antigen and DHBV-DNA was measured by immunohistochemistry and in situ hybridization, respectively.. Viraemia became undetectable in the penciclovir-treated animals at day 17, following 8 days of therapy. Examination of liver tissue revealed that all hepatocytes and the majority of BDEC contained DHBV preS1 antigen and DHBV-DNA. Penciclovir greatly reduced the intrahepatic viral burden, but there was no antiviral effect on viral markers within BDEC. Despite the increased number of BDEC after bile duct ligation, the same proportion of BDEC was seen to be infected, and this was unaffected by antiviral therapy.. In the duck model with and without biliary hyperplasia, penciclovir controls DHBV replication and reduces viral burden in hepatocytes, but not in BDEC. The BDEC appear to be an important reservoir of virus that is relatively unaffected by antiviral treatment, and may play an important role in disease persistence and relapse following cessation of therapy.

Topics: Acyclovir; Animals; Antiviral Agents; Bile Ducts; Cell Division; Disease Models, Animal; DNA, Viral; Ducks; Epithelial Cells; Guanine; Hepadnaviridae Infections; Hepatitis B Surface Antigens; Hepatitis B Virus, Duck; Hyperplasia; In Situ Hybridization; Liver; Protein Precursors; Reverse Transcriptase Inhibitors; Treatment Outcome; Viral Envelope Proteins; Virus Replication

A new method for the preparation of 8-[(18)F]fluoroguanine derivatives based on a direct radiofluorination reaction has been developed. The radiofluorination of ganciclovir (1a) with [(18)F]F(2) was carried out in absolute ethanol in the presence of tetraethylammonium hydroxide at room temperature to give 8-[(18)F]fluoroganciclovir (3a) in an approximately 1% radiochemical yield. Similarly, 8-[(18)F]fluoropenciclovir (3b), 8-[(18)F]fluoroacyclovir (3c), and 8-[(18)F]fluoroguanosine (3d) were synthesized from penciclovir (1b), acyclovir (1c), and guanosine (1d), respectively, using [(18)F]F(2). The structural analyses of the final products (3a, 3b, 3c, and 3d) were carried out after (18)F decay by (1)H, (13)C, and (19)F nuclear magnetic resonance and high resolution mass spectroscopy.

Topics: Acyclovir; Ganciclovir; Gene Expression; Guanine; Guanosine; Isotope Labeling; Magnetic Resonance Spectroscopy; Radiopharmaceuticals; Tomography, Emission-Computed

The in vitro antiviral activity of a new series of cycloSal-pro-nucleotides derived from the acyclic nucleoside analogues aciclovir and penciclovir against herpes simplex virus type 1 (HSV-1), thymidine kinase deficient (TK-) HSV-1, and Epstein-Barr virus (EBV) was evaluated. Using the XTT-based tetrazolium reduction assay EZ4U, the cycloSal derivatives were examined for their antiviral and cytotoxic effects in HSV-1 as well as HSV-1-TK--infected Vero cells. The anti-EBV activity was assessed by means of an EBV DNA hybridization assay using a digoxigenin-labeled probe specific for the Bam H1-W-fragment of the EBV genome and by measuring viral capsid antigen (VCA) expression in P3HR-1 cells by indirect immunofluorescence. Among the new cycloSal-phosphotriesters the three aciclovir monophosphates proved to be potent and selective inhibitors of HSV-1 replication, EBV DNA synthesis and EB-VCA expression. Of interest is the retention of activity of the aciclovir monophosphates in HSV-1-TK--infected cells. Particularly 3-methyl-cycloSal-aciclovir monophosphate retained the same effectiveness, as compared to the wild type virus strain. In contrast to the aciclovir pro-nucleotides the penciclovir cycloSal-phosphotriesters exhibited at best only a marginal antiviral effect on HSV and EBV replication.

Topics: Acyclovir; Animals; Antigens, Viral; Antiviral Agents; Capsid Proteins; Cells, Cultured; Chlorocebus aethiops; DNA, Viral; Guanine; Herpesvirus 1, Human; Herpesvirus 4, Human; Thymidine Kinase; Vero Cells; Virus Replication

Herpes simplex virus (HSV) infections in 75 allogeneic stem cell transplant recipients were analyzed. Sixteen patients developed HSV disease following transplantation. The risk factors were age, sex (females), unrelated donor graft, and graft-versus-host disease (GVHD) grade >/=2. Seven patients did not respond to acyclovir, and 3 patients failed to respond to foscarnet. Isolates from 4 patients developed resistance to acyclovir/penciclovir, and 3 patients had foscarnet-resistant isolates. The remaining 3 patients failed to respond to acyclovir, despite having sensitive isolates. All the isolates were sensitive to cidofovir, for which the IC(50) values correlated inversely with those for acyclovir (P=.01). The risk factors for clinical resistance to antiviral drugs were a GVHD grade >/=2 (P=.001) and the lack of ganciclovir prophylaxis (P=.01), with a higher nonrelapse mortality in the latter group (P<.0001). Clinical as well as in vitro resistance to antiviral drugs is common in patients with severe GVHD and is associated with a poor outcome.

Topics: Acyclovir; Adolescent; Adult; Antiviral Agents; Drug Resistance; Female; Ganciclovir; Graft vs Host Disease; Guanine; Hematopoietic Stem Cell Transplantation; Herpes Simplex; Humans; Male; Middle Aged; Prognosis; Risk Factors; Transplantation, Homologous

Topics: 2-Aminopurine; Acyclovir; Antiviral Agents; Drug Industry; Famciclovir; Guanine; Humans; South Africa

L-Nucleoside analogs are new therapeutic agents for treatment of chronic hepatitis B. However, their clinical application was limited by the emergence of viral resistance. It is important to develop a new system to evaluate drug cross-resistance and to test new agents that may overcome resistant virus. In this report, three cell lines HepG2-WT10, HepG2-SM1, and HepG2-DM2 are presented; these cell lines were established by transfection of HepG2 cells with unique fully functional 1.1x hepatitis B virus (HBV) genomes: wild-type HBV-adr and its L526M and L526MM550V variants, respectively. We have demonstrated that these genomes have different susceptibilities to lamivudine [L(-)SddC] and penciclovir (PCV). By examining HBV RNA transcription, antigen expression, progeny DNA replication, and viral susceptibilities to L(-)SddC, PCV, and other nucleoside analogs, it is concluded that the cell lines are able to stably produce L(-)SddC- and PCV-sensitive and -resistant HBV virions. In addition, the relative susceptibilities of the wild-type and mutant HBV produced from the stably transfected cell lines to several anti-HBV nucleoside analogs were also examined and found to be about the same as those found by using a transient infection system. PMEA [9-(2-phosphonylmethoxytehyl)-adenine] and QYL685 are able to suppress L(-)SddC- and PCV-resistant HBV. In conclusion, this cell culture system is a novel and useful tool for evaluating anti-HBV compounds and biologics.

Topics: Acyclovir; Antigens, Viral; Antiviral Agents; Carcinoma, Hepatocellular; Drug Resistance, Microbial; Guanine; Hepatitis B virus; Humans; Lamivudine; Liver Neoplasms; Microbial Sensitivity Tests; Time Factors; Transfection; Tumor Cells, Cultured; Virus Replication

Mycophenolic acid [the active metabolite of the immunosuppressive agent mycophenolate mofetil (MMF)] and ribavirin were found to potentiate the anti-HBV activity of the guanine-based nucleoside analogues penciclovir (PCV), lobucavir (LBV) and 3'-fluorodideoxyguanosine (FLG) and diaminopurine dioxolane (DAPD). Ribavirin and mycophenolic acid are both inhibitors of inosine 5'-monophosphate dehydrogenase and cause a depletion of intracellular dGTP levels. It may be assumed that the 5'-triphosphorylated derivatives of the guanine-based nucleoside analogues, in the presence of reduced levels of dGTP, inhibit more efficiently the priming reaction as well as the reverse transcription and DNA-dependent DNA polymerase activity of the HBV polymerase. This assumption is corroborated by the observation that exogenously added guanosine reversed the potentiating effect of ribavirin and mycophenolic acid on the anti-HBV activity of the guanosine analogues. Our observations may have implications for those (liver) transplant recipients that receive MMF as (part of their) immunosuppressive regimen and that, because of de novo or persistent infection with HBV, need specific anti-HBV therapy.

Topics: Acyclovir; Antiviral Agents; Cell Line; Dideoxynucleosides; Dioxolanes; Drug Synergism; Filaggrin Proteins; Guanine; Guanosine; Hepatitis B; Hepatitis B virus; Humans; Mycophenolic Acid; Purine Nucleosides; Ribavirin; Virus Replication

The antiviral effect of acyclovir elaidate in the female guinea pig model of genital herpes was investigated in a series of experiments. The antiherpesvirus effects of this novel compound, 9-(2'-[trans-9"-octadecenoyloxyl]ethoxymethyl)guanine (code no. P-4010), were studied in both primary and recurrent genital herpes in the female guinea pig, following oral gavage or intraperitoneal injection, with different formulations of the compound, and in comparison with acyclovir (ACV) or penciclovir (PCV). The results indicate that compound P-4010 has a greater capability than either ACV or PCV in reducing the clinical symptoms of primary genital herpes induced following the inoculation of herpes simplex virus type 2 (HSV-2) intravaginally into guinea pigs. In addition, the administration of P-4010 twice daily over a 10-day period by the intraperitoneal route (15 to 40 mg/kg of body weight/day) or by oral gavage (50 to 200 mg/kg/day), commencing 4 h subsequent to intravaginal HSV-2 infection, resulted in a degree of reduction in the incidence and severity of spontaneous, recurrent genital herpes in these animals. The findings are discussed in the light of the value and relevance of the female guinea pig model of genital herpes for the assessment of anti-herpes simplex virus compounds.

Topics: Acyclovir; Administration, Oral; Animals; Antiviral Agents; Female; Guanine; Guinea Pigs; Half-Life; Herpes Genitalis; Humans; Injections, Intraperitoneal; Oleic Acid; Oleic Acids; Recurrence; Urinary Retention; Vagina

We have characterized the differential actions of acyclovir and penciclovir against varicella-zoster virus (VZV) in cell culture by comparing the frequency of appearance of resistant viruses followed by their characterization. Cells were infected with cell-free virus and the cultures were successively treated with increasing concentrations of acyclovir or penciclovir. Drug-resistant viruses were selected in the presence of 6 microg/ml of acyclovir or penciclovir. The emergence frequency of resistant viruses was significantly higher following acyclovir exposure than following penciclovir exposure (Fisher's exact test, P<0.0001), possibly reflecting virus growth differences under these experimental conditions. Based on antiviral drug susceptibility and thymidine kinase (TK) activity assays, 11 acyclovir-resistant variants from seven experiments using three virus strains (Kawaguchi strain, Oka varicella vaccine strain and a clinical isolate from a zoster patient) were found to be TK-deficient. Sequence analysis of TK-deficient variants of the Kawaguchi strain revealed deletions that caused frameshifts, resulting in premature termination in the TK gene.

Topics: Acyclovir; Antiviral Agents; Cells, Cultured; DNA, Viral; Drug Resistance, Microbial; Genes, Viral; Guanine; Herpes Zoster; Herpesvirus 3, Human; Humans; Lung; Microbial Sensitivity Tests; Sequence Analysis, DNA; Thymidine Kinase; Viral Plaque Assay

The amino acid ester derivatives of 6-deoxypenciclovir, 11-20, were synthesized as potential prodrugs of penciclovir, and were evaluated for their oral penciclovir bioavailability in mice and rats. Esterification of 6-deoxypenciclovir with N-carbobenzyl-oxyglycine, -L-alanine, -L-valine, -L-leucine, or -L-isoleucine (3.75equiv.) using conventional coupling method (DCC/DMAP) afforded the mono-O-ester derivatives 1-5 in 47-55% yields as a mixture of two diastereomers along with the di-O-ester derivatives 6-10 in 20-29% yields. Reductive cleavage of carbobenzyloxy (Cbz) group (10% Pd/C, 1 atmosphere of H2, room temperature in methanol) followed by subsequent treatment of the resulting free amine with methanolic HCI solution provided the mono-O-ester derivatives 11-15 as di-HCl salt in 51-98% yields and the di-O-ester derivatives 16-20 as tri-HCl salt in 65 98% yields. Of the prodrugs tested in mice and rats, 6-deoxypenciclovir O-L-valinate (13), O-L-isoleucinate (15), and O,O-di-glycinate (16) showed significantly higher urinary recovery of penciclovir compared with that of penciclovir, but those are somewhat lower than that of famciclovir.

Topics: Acyclovir; Animals; Antiviral Agents; Biological Availability; Chromatography, High Pressure Liquid; Esters; Guanine; Magnetic Resonance Spectroscopy; Male; Mice; Mice, Inbred ICR; Models, Chemical; Rats; Spectrophotometry

2-Amino-6-fluoro-9-(4-hydroxy-3-hydroxymethylbut-1-yl)purine (7), and its mono- and diesters 8-15 were prepared and evaluated for their potential as prodrugs of penciclovir. Treatment of 2-amino-6-chloro-9-(4-hydroxy-3-hydroxymethylbut-1-yl)purine (5) with trimethylamine in THF followed by a reaction of the resulting trimethylammonium chloride salt 6 with KF in DMF afforded 2-amino-6-fluoro-9-(4-hydroxy-3-hydroxymethylbut-1-yl)purine (7) in 80% yield. Esterification of 7 with an appropriate acid anhydride [Ac2O, (EtCO)2O, (n-PrCO)2O, or (i-PrCO)2O] in DMF in the presence of a catalytic amount of DMAP produced the mono-esters 8-11 in 42-45% yields and diesters 12-15 in 87-99% yields. Of the prodrugs tested in rats, the monoisobutyrate 11 was the most efficiently absorbed and metabolized to 7, showing the mean maximum total concentration of penciclovir (5.5 microg/mL) and 7 (10.8 microg/mL) in the blood was much higher than the mean maximum concentration of penciclovir (11.5 microg/mL) from famciclovir. However, the mean concentrations of penciclovir from 11 were lower than those from famciclovir because of the limited conversion of a major metabolite 7 to penciclovir by adenosine deaminase.

Topics: Acyclovir; Animals; Antiviral Agents; Biological Availability; Esters; Guanine; Molecular Structure; Prodrugs; Rats; Rats, Sprague-Dawley; Spectrum Analysis

L-(-)2',3'-Dideoxythiacytidine (L(-)SddC, Lamivudine) resistant hepatitis B virus (HBV) develops in patients after prolonged treatment. Point mutations detected in the viral genome from these patients have been shown to be responsible for L(-)SddC resistance. Therefore, new drugs active against L(-)SddC resistant HBV are needed. Using a transient transfection system, we studied the sensitivity of L(-)SddC resistant HBV to other anti-HBV nucleoside analogues. It was found that the L526M mutation alone caused greater resistance to penciclovir (PCV) than did the V553I mutation alone. Both mutations also caused the virus to be less sensitive to L(-)SddC and 2'-fluoro-5-methyl-beta-L-arabinofuranosyluracil (L-FMAU), although the degree of resistance was much less than that to PCV. The A546V mutation had no impact on the sensitivity to L(-)SddC, L-FMAU, and PCV. When these single mutations were coupled with the M550V/I mutation, all the double mutants were resistant to those drugs. Although 2',3'-dideoxy-2',3'-didehydro-beta-L(-)-5-fluorocytidine (L(-)Fd4C) was also less active, the IC50 of L(-)Fd4C against the L(-)SddC resistant mutant was at least fifty times lower than that against cell growth in culture. DNA polymerase associated with L(-)SddC resistant virions was also found to be less sensitive than that with wild-type HBV to those L-nucleoside triphosphates. All the L(-)SddC resistant mutants were still sensitive to 9-(2-phosphonylmethoxyethyl)-adenine (PMEA). These results suggest that different mutations in the HBV genome have a different impact on its sensitivity to those compounds, and L(-)SddC resistant HBV may also be resistant to PCV, L-FMAU, and L(-)Fd4C. A nucleoside analogue less toxic than PMEA could be developed against L(-)SddC resistant HBV.

Topics: Acyclovir; Adenine; Antiviral Agents; Arabinofuranosyluracil; DNA-Directed DNA Polymerase; Drug Resistance, Microbial; Drug Resistance, Multiple; Guanine; Hepatitis B virus; Lamivudine; Microbial Sensitivity Tests; Mutation; Nucleic Acid Synthesis Inhibitors; Organophosphonates; Zalcitabine

The emergence of resistant hepatitis B virus (HBV), with mutations in the YMDD motif of the polymerase gene after treatment with lamivudine, is becoming an important clinical problem. In this study, susceptibility of wild-type and lamivudine-resistant HBV M552I, M552V, and L528M/M552V mutants to other reverse transcriptase inhibitors was investigated by transient transfection of full-length HBV DNA into human hepatoma cells. HBV DNA replication was monitored by Southern blot hybridization, which showed the presence of a single-stranded band (representative of the HBV replicative intermediates) in the drug-free, wild-type HBV-transfected cells. This band was diminished in the samples of wild-type HBV DNA treated with either lamivudine, adefovir, or lobucavir. The band intensities from the lamivudine-resistant mutants were not decreased by treatment with lamivudine, but were decreased by the treatments with adefovir or lobucavir. In contrast, penciclovir and nevirapine did not diminish the intensity of the single-stranded band of wild-type HBV or the lamivudine-resistant mutants. These results demonstrate that lamivudine-resistant HBV is susceptible to adefovir and lobucavir. Lamivudine-resistant HBV should be treated with adefovir or lobucavir, and combination therapy with lamivudine and adefovir/lobucavir may prevent the emergence of lamivudine-resistant HBV.

Topics: Acyclovir; Adenine; Carcinoma, Hepatocellular; Drug Resistance, Microbial; Guanine; Hepatitis B virus; Humans; Lamivudine; Mutagenesis, Site-Directed; Nevirapine; Organophosphonates; Reverse Transcriptase Inhibitors; Transfection; Tumor Cells, Cultured

Although 7-hydroxymethotrexate is a major metabolite of methotrexate during high-dose therapy, negligible methotrexate-oxidizing activity has been found in-vitro in the liver in man. The goals of this study were to determine the role of aldehyde oxidase in the metabolism of methotrexate to 7-hydroxymethotrexate in the liver and to study the effects of inhibitors and other substrates on the metabolism of methotrexate. Methotrexate, (+/-)-methotrexate and (-)-methotrexate were incubated with partially purified aldehyde oxidase from the liver of rabbit, guinea-pig and man and the products analysed by HPLC. Rabbit liver aldehyde oxidase was used for purposes of comparison. In-vitro aldehyde oxidase from the liver of man catalyses the oxidation of methotrexate to 7-hydroxymethotrexate, but the turnover is low. However, formation of 7-hydroxy-methotrexate from all forms of methotrexate by the liver in guinea-pig and man was significantly inhibited in the presence of 100 microM menadione and chlorpromazine, potent inhibitors of aldehyde oxidase. Allopurinol (100 microM) had a negligible inhibitory effect on liver aldehyde oxidase from guinea-pig and man. Allopurinol is a xanthine oxidase inhibitor. The production of 7-hydroxymethotrexate was enhanced in the presence of allopurinol. Although aldehyde oxidase is also responsible for some of this conversion, it is also possible that the closely related xanthine oxidase is responsible for the formation of 7-hydroxymethotrexate. By employing potent selective inhibitors of aldehyde oxidase, menadione and chlorpromazine, we have demonstrated for the first time that liver aldehyde oxidase from man is minimally involved in methotrexate oxidation.

Topics: Acyclovir; Aldehyde Oxidase; Aldehyde Oxidoreductases; Allopurinol; Animals; Chlorpromazine; Enzyme Inhibitors; Guanine; Guinea Pigs; Humans; Kinetics; Liver; Methotrexate; Oxidation-Reduction; Rabbits; Species Specificity; Stereoisomerism; Substrate Specificity; Vitamin K

The anti-herpesvirus activity of (1'S,2'R)-9-[[1',2'-bis(hydroxymethyl)cycloprop-1'-yl]methyl]guani ne (A-5021) was evaluated in murine cells and in several murine models of herpes simplex virus (HSV) infection. Against HSV type 1 (HSV-1), A-5021 was 15-30- and 30-60-fold more active, and against HSV type 2 (HSV-2), it was 2- and 8-fold more active than acyclovir and penciclovir in Balb/3T3 cells, respectively. When antiviral compounds were administered orally (once daily) to mice infected intraperitoneally with HSV-1 (Tomioka), A-5021 was more active than acyclovir or famciclovir in spite of its relatively low oral bioavailability. A-5021 was as active as penciclovir when the antiviral compounds were given intravenously (three times daily) to mice infected intraperitoneally with HSV-2 (186). In mice with a cutaneous HSV-1 (KOS) infection, three times daily oral therapy with A-5021 at 25 mg/kg per day produced more significant reduction in severity of skin lesions than equivalent treatment with acyclovir or famciclovir. In mice infected intracerebrally with HSV-1 (Tomioka), complete survival was observed in the group treated intravenously with A-5021 at 25 mg/kg per day (three times daily), while more than 50% of mice died in the groups treated intravenously with acyclovir of up to 100 mg/kg per day (three times daily). Moreover, A-5021 was more effective than acyclovir in clearing infectious virus from the brain. These findings demonstrate that A-5021 has potent anti-HSV activity in several murine models.

Topics: 3T3 Cells; Acyclovir; Administration, Oral; Animals; Antiviral Agents; Area Under Curve; Disease Models, Animal; Drug Evaluation; Encephalitis; Guanine; Herpes Simplex; Injections, Intravenous; Male; Mice; Mice, Inbred BALB C; Microbial Sensitivity Tests; Peritoneum; Simplexvirus; Skin; Survival Rate

A series of 2-amino-9-(3-acyloxymethyl-4-alkoxycarbonyloxybut-1-yl)purin es (1-8) and 2-amino-9-(3-alkoxycarbonyl-oxymethyl-4-alkoxycarbonyloxybut -1-yl)purines (9-12) were synthesized as potential prodrugs of penciclovir. Treatment of 6-deoxypenciclovir with trimethyl orthoacetate or triethyl orthopropionate (1.2 equiv) in DMF in the presence of p-TsOH.H2O (0.1 equiv) followed by quenching with excess H2O gave the corresponding mono-O-acetyl or mono-O-propionyl compound, 17 or 18, in excellent yields of 95 and 92%, respectively. Reactions of 17 or 18 with an appropriate alkyl (Me, Et, n-Pr, and i-Pr) 4-nitrophenyl carbonate (1.2 equiv) in pyridine in the presence of a catalytic amount of DMAP (0.1 equiv) at 80 degrees C afforded the monoacyl, monocarbonate derivatives of 6-deoxypenciclovir, 1-8, in 86 94% yields. Similar reactions of 6-deoxypenciclovir with 2.1 equiv of alkyl 4-nitrophenyl carbonate produced the dicarbonate derivatives 9 12 in 81-83% yields. Of the prodrugs tested in rats, 2-amino-9-(3-acetoxymethyl-4-isopropoxycarbonyloxybut-1-yl)purine (4) achieved the highest mean urinary recovery of penciclovir (36%), followed in order by compounds 2 (35%), 6 (35%), 7 (34%), 10 (34%), 8 (32%), 3 (32%), and famciclovir (31%). The mean urinary recovery of penciclovir and concentrations of penciclovir in the blood from 4 in mice were also slightly higher than those from famciclovir. The in vivo antiviral efficacy of 4 in HSV-1-infected normal BALB/c mice was higher than those of famciclovir and valaciclovir in terms of mortality (100, 80, and 40%) and mean survival time ( > 21, 13+/-5.0 (SEM), and 13+/-1.6 days). Compound 4 demonstrated an effective anti-hepadnaviral response with intrahepatic viral load being reduced by 90%, the viral supercoiled DNA levels reduced by 70% and Pre-S expression inhibited by 30% against duck hepatitis B virus (DHBV) in vivo, and did not cause any significant hepatotoxicity after 4 weeks of treatment.

Topics: Acyclovir; Animals; Antiviral Agents; Biological Availability; Ducks; Evaluation Studies as Topic; Female; Guanine; Male; Mice; Mice, Inbred BALB C; Mice, Inbred ICR; Prodrugs; Purines; Rats; Rats, Sprague-Dawley; Spectrum Analysis

Topics: 2-Aminopurine; Acetamides; Acyclovir; Aged; Amantadine; Animals; Anti-HIV Agents; Antiviral Agents; Child; Child, Preschool; Dose-Response Relationship, Drug; Drug Resistance, Microbial; Enzyme Inhibitors; Famciclovir; Ganciclovir; Guanidines; Guanine; Herpes Simplex; Herpes Zoster; History, 18th Century; HIV Infections; Humans; Injections, Intravenous; Interferon-alpha; Lamivudine; Neuraminidase; Oseltamivir; Pyrans; Rats; Ribavirin; Sialic Acids; Teratogens; Valacyclovir; Valine; Zanamivir

We compared the penciclovir susceptibilities and pathogenesis phenotypes of mutants of Herpes simplex virus type 1 that are resistant to acyclovir and/or foscarnet. The mutants, which were derived from laboratory strain KOS, included six DNA polymerase mutants, a thymidine kinase negative mutant, a thymidine kinase partial mutant, and a double mutant. Two of four polymerase mutants not previously examined for penciclovir susceptibility exhibited modest resistance to this drug. A thymidine kinase negative mutant exhibited approximately 20-fold resistance while a thymidine kinase partial mutant was penciclovir-sensitive. Following intracerebral inoculation of 7-week old CD1 mice, the mutants ranged from exhibiting near wild-type neurovirulence (thymidine kinase partial) to modest attenuation (e.g. thymidine kinase negative) to more severe attenuation. Following corneal inoculation, three polymerase mutants exhibited modest deficits (relative to those of thymidine kinase negative mutants) in their abilities to replicate acutely in the ganglion and reactivate from latency. For mutant AraA(r)13, the deficit in ganglionic replication was shown to be due to its polymerase mutation by analysis of recombinant viruses derived by marker rescue. These results may have implications for issues of penciclovir action and resistance, for drug resistance in the clinic, and for the interactions of herpes viruses with the peripheral and central nervous systems.

Topics: Acyclovir; Animals; Antiviral Agents; Chlorocebus aethiops; Cornea; Drug Resistance, Microbial; Genes, pol; Guanine; Herpes Simplex; Herpesvirus 1, Human; Mice; Mutation; Phenotype; Thymidine Kinase; Trigeminal Ganglion; Vero Cells; Viral Plaque Assay; Virulence; Virus Latency; Virus Replication

The immunosuppressive agent mycophenolate mofetil (MMF) has been approved for use in kidney transplant recipients and may thus be used concomitantly for the treatment of intercurrent herpesvirus infections with drugs such as acyclovir (ACV), ganciclovir (GCV), and penciclovir (PCV). We found that MMF and its parent compound mycophenolic acid (at concentrations that are attainable in plasma) strongly potentiate the antiherpesvirus (herpes simplex virus [HSV] type 1 [HSV-1], HSV-2, thymidine kinase-deficient [TK-] HSV-1, both wild-type and TK- varicella-zoster virus, and human cytomegalovirus) activities of ACV, PCV, and GCV (up to 350-fold increases in their activities). The mechanism of potentiation was found to reside in the depletion of endogenous dGTP pools, which favored the inhibitory effect of the triphosphate of ACV, GCV, or PCV on the viral DNA polymerase. The combination of topically applied 5% MMF with 0.1% ACV strongly protected against HSV-1-induced cutaneous lesions in hairless mice, whereas therapy with either compound used singly had no protective effect. Interestingly, the combination of topically applied 5% MMF with 5% ACV was also highly effective in protecting against TK- HSV-2-induced cutaneous lesions (that were refractory to ACV treatment) in athymic nude mice. Topical therapy with MMF was very well tolerated, and no signs of irritation were observed. When given perorally at 200 mg/kg of body weight/day, MMF potentiated to some extent the growth retardation induced by GCV in young NMRI mice. These observations may have clinical implications (i) for those transplant recipients who receive both MMF and either ACV, GCV, or PCV and (ii) for the treatment of ACV-resistant mucocutaneous HSV infections.

Topics: Acyclovir; Animals; Antiviral Agents; Cells, Cultured; Chlorocebus aethiops; Deoxyguanine Nucleotides; Drug Synergism; Drug Therapy, Combination; Ganciclovir; Guanine; Herpes Genitalis; Herpes Simplex; Herpesvirus 1, Human; Herpesvirus 2, Human; Immunosuppressive Agents; Mice; Mice, Nude; Mycophenolic Acid; Vero Cells

Topics: Acyclovir; Antiviral Agents; Guanine; Herpes Labialis; Humans

Synthesis and preliminary biological evaluation of 9-(4-[18F]-fluoro-3-hydroxymethylbutyl)-guanine ([18F]FHBG) is reported. 9-(4-Hydroxy-3-hydroxymethylbutyl)-guanine (penciclovir) 4 was converted to 9-[N2, O-bis-(methoxytrityl)-3-(tosylmethybutyl)]guanine 7 by treatment with methoxytrityl chloride followed by tosylation. The tosylate 7 was reacted with either tetrabutylammonium fluoride or KF in the presence of kryptofix 2.2.2. to produce the 4-fluoro-N2-O-bis-(methoxytrityl) derivative 8. Removal of the methoxytrityl groups by acidic hydrolysis produced FHBG 5. Radiolabeled product [18F]FHBG was prepared by fluorination of the tosylate 7 with [18F]KF and kryptofix 2.2.2. The labeled product was isolated by HPLC purification on a reverse-phase C18 column, and eluted at 12 min with 15% acetonitrile in water at a flow rate of 2.25 mL/min. Radiochemical yield was 8.0-22.3% with an average of 12% in 7 runs (corrected for decay). Synthesis time was 90 to 100 min including HPLC purification with radiochemical purity >99%, and average specific activity of 320 mCi/micromol. In vitro studies of the compound in HT-29 colon cancer cells revealed 18.2-fold higher uptake into transduced cells compared to control in 3 h. The agent may be useful for imaging viral infection or transfected cells in gene therapy.

Topics: Acyclovir; Antiviral Agents; Biological Transport; Colonic Neoplasms; Fluorine Radioisotopes; Genetic Therapy; Guanine; Humans; Indicators and Reagents; Molecular Structure; Radionuclide Imaging; Tumor Cells, Cultured; Virus Diseases

To compare trifluridine eyedrops, cidofovir eyedrops, and penciclovir ophthalmic ointment for the treatment of herpes simplex virus type 1 keratitis.. New Zealand white rabbits were infected with the McKrae strain of herpes simplex virus type 1. Three days after viral inoculation, the rabbits were randomly assigned to treatment with 1% trifluridine, 0.2% cidofovir, 3% penciclovir ointment, or phosphate-buffered saline (for control) on various schedules. The severity of keratitis was graded in a masked manner.. Treatment with any of the antiviral drugs resulted in significantly less severe keratitis than treatment with phosphate-buffered saline. There was no statistically significant difference between eyes given trifluridine 2, 4, or 7 times a day and eyes given cidofovir 2 times a day (P=.06, P=.43, and P=.19, respectively, using the F test of the analysis of variance). Cidofovir given twice a day was significantly more effective than penciclovir given either 2 or 4 times a day (P<.001 and P=.002, respectively). Even with once-a-day dosage, all 3 drugs were significantly more effective than phosphate-buffered saline (P<.001 for all). There was no significant difference between once-a-day trifluridine and cidofovir treatments (P=.17). Trifluridine administered 5 times a day was as effective as 1% cidofovir. A similar degree of punctate keratitis was seen after 4 to 5 days in eyes treated with trifluridine at the highest frequency, 1% cidofovir, or penciclovir ointment.. Trifluridine treatment was highly effective in this rabbit model, even when given only once a day. Treatment with cidofovir was as effective as that with trifluridine.. Cidofovir and penciclovir treatments may prove to be effective against epithelial keratitis. Clinical trials of trifluridine, cidofovir, and penciclovir with lower treatment frequencies appear to be warranted.

Topics: Acyclovir; Animals; Antiviral Agents; Cidofovir; Cornea; Cytosine; Disease Models, Animal; Female; Guanine; Herpesvirus 1, Human; Keratitis, Herpetic; Male; Ointments; Ophthalmic Solutions; Organophosphonates; Organophosphorus Compounds; Rabbits; Trifluridine

Ducks congenitally infected with duck hepatitis B virus (DHBV) were treated with the antiviral guanine nucleoside analog penciclovir for 12 or 24 weeks at a dosage of 10 mg/kg of body weight per day. By the completion of both 12 and 24 weeks of therapy, molecular hybridization studies of the liver tissue revealed that the viral DNA, RNA, and protein levels were significantly reduced compared to those in the placebo-treated controls. Penciclovir treatment for 12 or 24 weeks was not associated with any toxicity, establishing the efficacy and safety of long-term penciclovir therapy in chronic DHBV infection.

Topics: Acyclovir; Animals; Antiviral Agents; Chronic Disease; DNA, Viral; Ducks; Guanine; Hepadnaviridae Infections; Hepatitis B Virus, Duck; Viral Proteins

A series of 2-amino-9-(3-hydroxymethyl-4-alkoxycarbonyloxybut-1-yl)purines (4-10) and 2-amino-9-(2-(2-oxo-1,3-dioxan-5-yl)ethyl)purine (1) were synthesized as potential prodrugs of penciclovir and evaluated for their oral penciclovir bioavailability in mice and rats. Treatment of 2-(2-benzyloxyethyl)propane-1,3-diol (11) with 1,1'-carbonyldiimidazole in THF followed by hydrogenolytic removal of the benzyl group of the resulting cyclic carbonate 12 gave 5-(2-hydroxyethyl)-1,3-dioxan-2-one (13). Mesylation of the alcohol 13 and then a coupling reaction of the resulting mesylate 14 with 2-amino-6-chloropurine using anhydrous Cs2CO3 in DMF afforded 2-amino-6-chloro-9-(2-(2-oxo-1,3-dioxan-5-yl)ethyl)purine (16) after purification by flash column chromatography on silica gel using EtOAc/MeCN/Et3N as eluent. Hydrogenation of the 6-chloro cyclic carbonate 16 followed by a ring-opening reaction of the 6-deoxy cyclic carbonate 1 in a mixture of an appropriate alcohol and CHCl3 using activated SiO2 as a Lewis acid afforded the corresponding alkyl monocarbonate derivatives 3-10 in fair to good yields. Of the prodrugs tested in mice, the isopropyl monocarbonate 6 achieved the highest mean urinary recovery of penciclovir (53%), followed in order by the propyl monocarbonate 5 (51%), the isopentyl monocarbonate 10 (51%), the ethyl monocarbonate 4 (50%), and famciclovir (48%). In rats, the methyl monocarbonate 3, 4, 6, the n-butyl monocarbonate 7, and 10 (39-41%) showed levels of mean urinary recovery of penciclovir similar to that from famciclovir (40%). The alkyl monocarbonates 4-10 were found to be quite stable in the aqueous buffer solutions, and among them, 6 was the most stable with the half-lives (t1/2) of 88, >200, 61, and 26 days at pH 1.2, 6.0, 7.4, and 8.0, respectively. In addition, 6 was highly soluble in H2O (138.8 mg/mL, 20 degrees C).

Topics: Acyclovir; Animals; Antiviral Agents; Biological Availability; Cell Line, Transformed; Chlorocebus aethiops; Drug Stability; Guanine; Herpesvirus 1, Human; Male; Mice; Prodrugs; Purines; Rats; Rats, Sprague-Dawley; Solubility; Vero Cells; Virus Replication

Robustaflavone, a naturally occurring biflavanoid isolated from Rhus succedanea, was found to be a potent inhibitor of hepatitis B virus (HBV) replication in 2.2.15 cells, with an effective concentration (EC50) of 0.25 microM, and a selectivity index (SI, IC50/EC90) of 153. Robustaflavone hexaacetate inhibited HBV replication with an EC50 of 0.73 microM, but exhibited no cytotoxicity at concentrations up to 1000 microM. Combinations of robustaflavone with penciclovir and lamivudine displayed synergistic anti-HBV activity, having the most pronounced effects when the combination ratios were similar to the ratio of EC50 potencies. Thus, a 1:1 combination of robustaflavone and penciclovir exhibited an EC50 of 0.11 microM and an SI of 684, while a 10:1 combination of robustaflavone and lamivudine exhibited an EC50 of 0.054 microM and an SI of 894. Statistical analyses of the combination data using the Combostat program confirmed that robustaflavone exhibited synergism with both penciclovir and lamivudine.

Topics: Acyclovir; Antiviral Agents; Biflavonoids; Cell Line; Drug Synergism; Flavonoids; Guanine; Hepatitis B virus; Lamivudine; Microbial Sensitivity Tests; Virus Replication

The synthesis of different cycloSal-phosphotriesters of the acyclic nucleoside analogues acyclovir (ACV), penciclovir (PCV) and T-penciclovir (T-PCV) as potential new lipophilic, membrane-soluble pronucleotides is described. The introduction of the cycloSal moiety was achieved by using reactive cyclic chlorophosphane reagents. In addition to the cycloSal-PCV monophosphate (MP) phosphotriesters, a second derivative bearing an acetyl group at the second primary alcohol function was prepared. In hydrolysis studies the cycloSal-ACVMPs showed the expected range of hydrolytic stability dependent on the substituent in the masking group (8-17 h). In contrast, the cycloSal-PCVMP derivatives exhibited a 11- to 15-fold increase in hydrolytic lability as compared to the corresponding cycloSal-ACVMP derivatives. We demonstrated that the free primary alcohol group is responsible for this rate acceleration because cycloSal-OAc-PCVMP, in which the hydroxyl group was blocked by acetylation, did not show the aforementioned acceleration. Unexpectedly, the hydrolysis product was not PCVMP but according to NMR and mass spectrometry it was cycloPCVMP (cPCVMP). The title compounds were evaluated in vitro for their ability to inhibit herpes simplex virus type 1 (HSV-1) and thymidine kinase-negative (TK-) HSV-1 replication in Vero cells. The cycloSal-ACVMP compounds exhibited high antiviral activity in HSV-1-infected cells. More importantly, one derivative retained all activity from the wild-type virus strain in HSV-1/TK(-)-infected Vero cells. The PCV derivatives were markedly less active. The reason for the failure of the cycloSal-PCVMPs seems to be due to the formation of cPCVMP instead of the desired PCVMP.

Topics: Acyclovir; Animals; Antiviral Agents; Chlorocebus aethiops; Guanine; Herpesvirus 1, Human; Magnetic Resonance Spectroscopy; Nucleosides; Nucleotides; Vero Cells; Virus Replication

Lamivudine ([-]-beta-L-2',3'-dideoxy-3'-thiacytidine [3TC]) and penciclovir (9-[2-hydroxy-1-(hydroxymethyl)ethoxymethyl]guanine [PCV]) are potent inhibitors of hepatitis B virus (HBV) replication. Both drugs have entered phase III clinical trials for treatment of chronic HBV infection. 3TC and PCV are deoxycytidine and deoxyguanosine analogs, respectively, and their modes of action and how they interact are matters of both theoretical and practical interest. We compared the antiviral activities of 3TC and PCV alone and in combination in primary duck hepatocyte (PDH) cultures derived from ducklings congenitally infected with the duck hepatitis B virus (DHBV). 3TC and PCV inhibited DHBV replication to a comparable extent when used alone (50% inhibitory concentrations with 95% confidence intervals were 0.55 [0.50-0.59] micromol/L for 3TC and 0.35 [0.27-0.43] micromol/L for PCV), and in combination, the two nucleoside analogs acted synergistically over a wide range of clinically relevant concentrations. Synergy between PCV and 3TC was also observed in acutely infected cells and in "washout" experiments designed to assess the persistence of antiviral activity after drug removal. Furthermore, the combination was more effective in reducing the normally recalcitrant viral covalently closed circular (CCC) DNA form of DHBV than either drug alone. These results suggest that combinations of 3TC and PCV may act synergistically against HBV in vivo.

Topics: Acyclovir; Animals; Antiviral Agents; Cells, Cultured; Dose-Response Relationship, Drug; Drug Synergism; Ducks; Guanine; Hepatitis B Virus, Duck; Lamivudine; Liver; Virus Replication

Topics: Acyclovir; Animals; Antiviral Agents; Cells, Cultured; Chronic Disease; Dose-Response Relationship, Drug; Drug Synergism; Drug Therapy, Combination; Guanine; Hepatitis B; Hepatitis B Virus, Duck; Humans; Lamivudine; Liver; Virus Replication

Topics: 2-Aminopurine; Abnormalities, Drug-Induced; Acyclovir; Amantadine; Antiviral Agents; Cidofovir; Contraindications; Cytosine; Drug Resistance, Microbial; Eye Infections, Viral; Famciclovir; Foscarnet; Ganciclovir; Guanine; Humans; Interferon-alpha; Kidney Diseases; Lamivudine; Organophosphonates; Organophosphorus Compounds; Prodrugs; Ribavirin; Rimantadine; Trifluridine; Valacyclovir; Valine; Virus Diseases

Topics: 2-Aminopurine; Acyclovir; Antiviral Agents; Famciclovir; Guanine; Herpes Labialis; Herpes Zoster; Humans; Valacyclovir; Valine

We used recombinant vaccinia viruses (rVV) containing the UL97 open reading frame (ORF) of the human cytomegalovirus (HCMV) to investigate the UL97-dependent phosphorylation of different nucleoside analogs. The rVV T1 expressed the wild-type UL97 protein whereas rVV A5 contained a 12 bp deletion in the UL97 which had been known to be responsible for resistance of HCMV to ganciclovir (GCV). The rVV T1opal was generated which contained a stop codon at position 1089 of the UL97 ORF and which expressed a truncated UL97 protein. We quantitatively analyzed the capability of these rVVs to phosphorylate GCV, penciclovir (PCV), aciclovir (ACV) and 2-amino-7-[(1,3-dihydroxy-2-propoxy)methyl] purine (S2242) as well as the natural nucleosides deoxycytidine and deoxythymidine. Moreover, we compared their phosphorylating capability with that of herpes simplex virus type 1 strains. In thymidine kinase (TK)-deficient 143B cells infected with rVV T1, the three compounds GCV, ACV and PCV were phosphorylated with different efficiency whereas in cells infected with the rVV A5 a markedly reduced but not completely abolished phosphorylation of these compounds was observed. In rVV T1opal-infected cells no specific phosphorylation of the compounds was detectable at all. Neither S2242 nor the natural substrates of TKs were phosphorylated by any of the vaccinia recombinants. The rVVs proved to be a suitable tool for analysis of UL97-dependent phosphorylation of nucleoside analogs and also allowed to quantitatively study the influence of UL97 mutations on drug phosphorylation.

Topics: Acyclovir; Antiviral Agents; Cells, Cultured; Ganciclovir; Guanine; Humans; Phosphorylation; Phosphotransferases (Alcohol Group Acceptor); Purines; Recombination, Genetic; Vaccinia virus

A DNA probe assay was compared with the plaque reduction assay to determine the sensitivity of clinical isolates of herpes simplex virus (HSV) and varicella-zoster virus (VZV) to penciclovir and acyclovir in MRC-5 cells. In both assays, penciclovir and acyclovir shared comparable activity against cell-free virus (CFV) preparations of VZV and herpes simplex virus type 1 (HSV-1) isolates, whilst acyclovir was significantly more active than penciclovir against herpes simplex virus type 2 (HSV-2) isolates in both the DNA probe assay (P < or = 0.01) and the plaque reduction assay (P < or = 0.01). However, the 50% effective concentrations (EC50s) were generally lower in the DNA probe assay and the correlation between the plaque reduction and DNA probe assays was poor for either compound. Six acyclovir-resistant strains of HSV-1 derived in cell culture were also tested for susceptibility to penciclovir and acyclovir, in the DNA probe and plaque reduction assays. The relative susceptibilities of these strains were comparable, for example, one ACV-resistant strain was susceptible to penciclovir in both assays. Further comparisons of the assay methods were made using cell-associated VZV (CAV). As with CFV the EC50s were significantly lower in the DNA probe assay than the plaque reduction assay for penciclovir (P < or = 0.01) and acyclovir (P < or = 0.01). In the DNA probe assay there was no significant difference in the EC50s for either penciclovir or acyclovir when comparing CAV with CFV. However, in the plaque reduction assay the EC50s for CAV were significantly higher than those for CFV for both penciclovir (P < or = 0.01) and acyclovir (P < or = 0.01). Overall the DNA probe assay is objective, does not require prior titration of isolates and provides opportunities for automation. It is more suitable for sensitivity testing of large numbers of clinical isolates than the well-established plaque reduction assay.

Topics: Acyclovir; Animals; Antiviral Agents; Cell Line; Cricetinae; DNA Probes; DNA, Viral; Guanine; Herpesvirus 1, Human; Herpesvirus 2, Human; Herpesvirus 3, Human; Humans; Sensitivity and Specificity; Simplexvirus; Viral Plaque Assay

Three purine nucleoside analogues, penciclovir (PCV), acyclovir (ACV) and ganciclovir (GCV), were assessed for in-vivo genotoxicity in the mouse bone marrow micronucleus assay, together with the xanthine (purine) analogue, caffeine (CAF). All these compounds exhibit anti-viral properties and the first three are marketed anti-viral drugs. All have been shown to be genotoxic in separate in-vitro and in-vivo studies. Because of their widespread use, we considered it important to directly compare their relative in-vivo genotoxic potencies as an aid to assessing their relative genotoxic risk to humans. Accordingly, two-dose (0 and 24 h)/single sample mouse micronucleus assays were performed on all four compounds. PCV and ACV appeared to give essentially arithmetic increases in induction of micronucleated polychromatic erythrocytes (MNPCE) with arithmetic increases in dose with apparent thresholds at approx. 1078 mumols/kg per day and 316 mumols/kg per day, respectively. The dose-response curve for GCV appeared more exponential, without a threshold, but with a no-effect dose of around 150 mumols/kg per day. With CAF, systemic toxicity allowed the assessment of only very weak effects, such that our estimate of a no-effect dose of 388 mumols/kg per day is subject to large errors. Taking into account magnitude of response, slope of dose-response curve and no-effect doses, the order of potency was GCV > ACV > (CAF?) > PCV. The relevance of these findings in terms of risk is uncertain.

Topics: Acyclovir; Animals; Antiviral Agents; Bone Marrow; Bone Marrow Cells; Caffeine; Dose-Response Relationship, Drug; Ganciclovir; Guanine; Male; Mice; Micronucleus Tests

The effect of penciclovir and acyclovir on the replication of herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2) strains was determined in MRC-5 cells infected with 0.01 pfu/cell and exposed to the drugs for 72 h to allow multiple cycles of replication. Penciclovir was significantly more active than acyclovir against three strains of HSV-1 and three strains of HSV-2 at 1 mg/L (P = 0.009), 3 mg/L (P < 0.001) and 10 mg/L (P = 0.001). Further comparisons between the compounds were made in MRC-5 cells infected with HSV-1 strain SC16 using four different antiviral assays namely, the 24 h virus yield reduction assay, plaque reduction assay, viral antigen inhibition assay, and a viral DNA inhibition assay, to determine the relative merits of each. Penciclovir and acyclovir shared similar activities in the plaque reduction assay (with 50% effective concentrations, EC50, being 0.8 and 0.6 mg/L, respectively) and in the viral antigen inhibition assay (EC50s. 0.6 and 0.7 mg/L, respectively). The EC50 of penciclovir in the 24 h viral DNA inhibition assay was 0.01 mg/L compared with 0.06 mg/L of acyclovir. In the 24 h virus yield reduction assay in which MRC-5 cells were infected with 0.3 pfu/cell, penciclovir was more active than acyclovir with 99% effective concentrations of 0.6 mg/L and 1.1 mg/L, respectively. The activity of penciclovir in the 24 h virus yield reduction and antigen inhibition assays was inversely related to the multiplicity of infection, whereas this had considerably less effect on the inhibition of viral DNA synthesis. These results suggest that famciclovir, which is the oral form of penciclovir, will be at least as effective as acyclovir in treating infections caused by HSV-1 and HSV-2.

Topics: Acyclovir; Antiviral Agents; Cell Line; Evaluation Studies as Topic; Guanine; Herpesvirus 1, Human; Herpesvirus 2, Human; Microbial Sensitivity Tests; Virus Replication

The HBV-producing human hepatoblastoma cell line, 2.2.15, has been shown to be an accurate model of chronic cellular viral infection and a predictive model of antiviral response for in vivo hepadnaviral infection. Our laboratory has utilized the 2.2.15 cell line in a standardized assay to examine treatment schemes which use combinations of clinically relevant nucleoside analogues, novel methods to deliver potentially useful nucleoside combinations, and treatments which simultaneously target different parts of the HBV replication pathway. For example, the combination of 3TC (lamivudine) with either alpha interferon or penciclovir significantly enhances the antiviral effectiveness of these agents against HBV replication in 2.2.15 cell culture.

Topics: Acyclovir; Antiviral Agents; Drug Synergism; Drug Therapy, Combination; Guanine; Hepatitis B; Hepatitis B virus; Hepatoblastoma; Humans; Interferon-alpha; Lamivudine; Tumor Cells, Cultured; Virus Replication; Zalcitabine

Penciclovir [9-(4-hydroxy-3-hydroxymethylbut-1-yI)guanine], an effective antiherpesvirus agent, was found to be a potent and selective antiviral agent against intracellular hepatitis B virus (HBV) replication (drug concentration at which a 10-fold decrease in HBV DNA from the average level in an untreated culture was observed [EC90], 1.6 microM) and extracellular virion release (EC90, 0.7 microM) by cultured human hepatoblastoma (2.2.15) cells. Acyclovir and three other related 9-alkoxypurines with activity against either herpesviruses or human immunodeficiency virus were uniformly inactive against HBV. The activity of penciclovir is discussed in relation to recent findings related to its mode of action against HBV.

Topics: Acyclovir; Antiviral Agents; Cell Line; Dideoxynucleosides; DNA-Directed DNA Polymerase; Guanine; Hepatitis B virus; Hepatoblastoma; Humans; Lamivudine; Microbial Sensitivity Tests; Virus Replication

The antiherpes virostatics acyclovir (ACV), valaciclovir (VACV), penciclovir (PCV), famciclovir (FCV) and ganciclovir (GCV), which belong to the group of purine acyclic nucleoside analogues, were tested for clastogenic and sister chromatid exchange (SCE)-inducing activity in Chinese hamster V79-E cells upon chronic application with and without a recovery period. ACV induced borderline effects in both cytogenetic assays, a dose-dependent reduction of the mitotic index and an increasing cell cycle delay. With VACV and PCV only a decrease of the mitotic index and an increase of cell cycle delay were observed. FCV was negative with respect to the four parameters studied, presumably due to the incapacity of the target cells of metabolizing FCV to PCV. GCV was a very potent genotoxin in both assays. It induced a statistically significant SCE response even in the range of the cytomegalovirus IC50 of < 10 microM. By variation of the experimental protocol it was shown that SCEs are induced in the second cell cycle following exposure to GCV but not in the first one. It is assumed that the drugs under study are metabolized to their respective triphosphates and then inhibit DNA replication as detected by decreasing mitotic index and increasing cell cycle delay. In the case of GCV it is suggested that GCV-TP is incorporated into the target cell DNA and that chromosomal aberrations and SCEs are secondary lesions due to repair processes at the substituted template.

Topics: 2-Aminopurine; Acyclovir; Animals; CHO Cells; Cricetinae; Famciclovir; Ganciclovir; Guanine; Mutagenicity Tests; Mutagens; Valacyclovir; Valine

Ducks congenitally infected with duck hepatitis B virus (HBV) were treated with the antiviral guanine nucleoside analog penciclovir for 4 weeks at a dose of 10 mg/kg of body weight per day. The effects of treatment on viremia and intrahepatic viral genome replication, transcription, and translation were examined. In seven of eight penciclovir-treated ducks, viremia was barely detectable after a week of treatment. After 4 weeks of treatment, molecular hybridization studies showed that intrahepatic viral DNA, RNA, and protein levels were significantly reduced compared with those in placebo-treated controls. Synthesis of all viral replicative intermediates, including the normally persistent viral supercoiled DNA species, was inhibited by penciclovir treatment. Examination of liver tissue sections after in situ DNA hybridization or immunohistochemical staining confirmed that viral DNA and protein synthesis had been profoundly inhibited in most hepatic parenchymal cells. However, small subpopulations of cells, in particular the small bile duct epithelial cells, remained strongly positive for duck HBV antigens and DNA despite treatment. There was no evidence of toxicity associated with penciclovir therapy. This study confirms the safety and potent antihepadnaviral activity of penciclovir in vivo but indicates that further improvements in antiviral therapy will be required to completely eliminate HBV infection.

Topics: Acyclovir; Animals; Antiviral Agents; Blotting, Southern; DNA, Viral; Ducks; Female; Guanine; Hepadnaviridae Infections; Hepatitis B Virus, Duck; Immunoblotting; Immunohistochemistry; In Situ Hybridization; Liver; Pancreas; RNA, Viral; Virus Replication

The deoxyguanosine analog penciclovir (PCV; 9-[4-hydroxy-3-hydroxymethyl-but-1-yl]guanine), has shown potent antiviral activity against herpes viruses and hepadnaviruses. Efficacy against chronic hepatitis B virus (HBV) infection has been demonstrated in an animal model and in recent clinical trials of famciclovir, the oral form of PCV. The antiviral activity of PCV is believed to be dependent on the intracellular formation of PCV-triphosphate (PCV-TP) which is presumed to inhibit HBV replication by interfering with viral DNA polymerase activity. The (S)-enantiomer is preferentially formed in herpes virus-infected cells, and is the more active against the herpes simplex virus; however, little is known about the biochemical mechanisms of PCV phosphorylation or of interference with viral replication in HBV-infected cells. Here, we report that in contrast with herpes simplex virus, the (R)-enantiomer of PCV-TP is a more potent inhibitor of HBV DNA polymerase-reverse transcriptase (pol-RT) in vitro than the (S)-enantiomer. In assays for HBV DNA pol-RT activity, in which purified viral core particles were the enzyme source, the IC50s for (R)- and (S)-enantiomers of PCV-TP were 2.5 micromol/L and 11 micromol/L, respectively. The estimated Kis for (R)- and (S)- PCV-TP were approximately 0.03 micromol/L and approximately .04 micromol/L, respectively, about 3-fold lower than the Km for deoxyguanosine triphosphate (dGTP) in the same system. In addition, we report that PCV metabolism is similar in both control (HepG2) and in HBV-transfected (2.2.15) hepatoblastoma cells in vitro, indicating that cellular enzyme(s) catalyze PCV phosphorylation. Peak PCV-TP concentrations of about .4 micromol/L were reached in both cell types in less than 12 hours, and intracellular PCV-TP was exceptionally stable with a half-life of about 18 hours. These observations provide a mechanistic basis for the potent activity of PCV against HBV.

Topics: Acyclovir; Antiviral Agents; DNA, Viral; Guanine; Hepatitis B virus; Humans; Nucleic Acid Synthesis Inhibitors; Stereoisomerism; Tumor Cells, Cultured; Virus Replication

Chronic hepatitis B virus (HBV) infection is a major health problem worldwide. Antiviral strategies available at present, including interferon-alpha, have only limited efficacy, leading us to analyse the antiviral effects of penciclovir and famciclovir in the duck hepatitis B virus (DHBV) model of HBV infection in vitro and in vivo. In DHBV-infected duck hepatocytes, penciclovir effectively inhibited viral replication, with a concentration giving half-maximal inhibition of 0.25 microM. Furthermore, in vivo, penciclovir and its orally administered prodrug famciclovir strongly inhibited DHBV replication. These data demonstrate that penciclovir and famciclovir both have strong antiviral activities, and suggest that these agents might be useful for treating HBV infection in humans.

Topics: 2-Aminopurine; Acyclovir; Animals; Antiviral Agents; Ducks; Famciclovir; Guanine; Hepadnaviridae Infections; Hepatitis B Virus, Duck; Hepatocytes; Virus Replication

Penciclovir inhibited the productive replication cycle of Epstein-Barr virus (EBV) in assays measuring infectious virus production, viral antigen expression, and viral DNA synthesis. In the test measuring inhibition of EBV DNA synthesis, 50% effective concentrations of penciclovir and acyclovir were 2.3 +/- 0.8 and 2.2 +/- 0.6 micrograms/ml, respectively. The 50% cell growth inhibitory concentration of penciclovir was > 100 micrograms/ml for both P3HR-1 and Raji cells. Penciclovir is a selective inhibitor of EBV in cell culture.

Topics: Acyclovir; Antigens, Viral; Antiviral Agents; B-Lymphocytes; Cells, Cultured; DNA, Viral; Enzyme-Linked Immunosorbent Assay; Guanine; Herpesvirus 4, Human; Humans; Virus Replication

1. Drug-related material was well absorbed following oral administration of 14C-famciclovir to the male rat at doses up to 4000 mg/kg and to the male dog at doses up to 250 mg/kg, as judged by the early onset of the peak blood or plasma concentrations of radioactivity (usually < or = 1.5h) and the rapid extensive excretion of radioactivity in the urine (57-76 and 86-89% of dose in rat and dog respectively). 2. Famciclovir underwent extensive first-pass metabolism in both species. In rat, following dosing at 40 mg/kg, famciclovir was rapidly and extensively metabolized to the active antiviral compound penciclovir, which reached peak concentrations in the plasma (mean 3.5 micrograms/ml) at 0.5 h. The 6-deoxy precursor of penciclovir, BRL 42359, was the only other major metabolite detected in rat plasma. Cmax values for BRL 42359 (mean 2.2 micrograms/ml) were also achieved at 0.5 h. In dog, extensive conversion of famciclovir to penciclovir, via BRL 42359, also occurred, but its rate of formation from BRL 42359 was somewhat slower than in rat. In dog, following dosing at 25 mg/kg, Cmax values for penciclovir (mean 4.4 micrograms/ml) occurred at 3 h and were lower than the Cmax values for BRL 42359 (mean 10.0 micrograms/ml) which were achieved at 1h. 3. A dose-dependent decrease in the conversion of BRL 42359 to penciclovir occurred in both species, resulting a changes in the ratios of the plasma concentrations of the two metabolites with increasing dose. In rat, the urinary excretion of penciclovir decreased from 36% of dose at 40 mg/kg to 21% at 4000 mg/kg, and was accompanied by a corresponding increase in the urinary excretion of BRL 42359. In dog, a similar decrease in the urinary excretion of penciclovir occurred on increasing the dose of famciclovir from 25 to 250 mg/kg. 4. Penciclovir and BRL 42359 were the major metabolites detected in urine and faeces. In rat, following dosing at 40 mg/kg, 54 and 22% of dose were recovered in the excreta as penciclovir and BRL 42359 respectively. Corresponding recoveries of the two metabolites in the dog were 34 and 50% of dose. The metabolic fate of famciclovir in these animal species is, therefore, similar to that reported previously in man.

Topics: 2-Aminopurine; Acyclovir; Animals; Antiviral Agents; Biotransformation; Blood Proteins; Chromatography, High Pressure Liquid; Dogs; Famciclovir; Feces; Guanine; Male; Mass Spectrometry; Protein Binding; Rats; Rats, Sprague-Dawley; Species Specificity; Spectrophotometry, Ultraviolet

High-performance liquid chromatography (HPLC) and capillary zone electrophoresis (CZE) were used in biodegradation kinetic studies. This paper describes a rapid penciclovir separation using CZE with detection limits comparable to HPLC. The ionic-strength mediated stacking technique was employed while good resolution was maintained. With a shorter analysis time, comparable detection limits and no organic solvent consumption, CZE is a better method for penciclovir biodegradation studies than conventional reversed-phase HPLC (RP-HPLC).

Topics: Acyclovir; Antiviral Agents; Biodegradation, Environmental; Chromatography, High Pressure Liquid; Electrophoresis, Capillary; Guanine; Reproducibility of Results; Spectrophotometry, Ultraviolet

Famciclovir is the diacetyl 6-deoxy derivative of the active antiviral penciclovir that is for use in the treatment of infections caused by the herpes family of viruses. The major pathway of conversion is via di-deacetylation to BRL 42359, followed by oxidation to penciclovir. On oral dosing of famciclovir to humans, only penciclovir and BRL 42359 can be detected consistently in the plasma; thus, attention was focused on the oxidation reaction. This 6-oxidation occurred rapidly in human liver cytosol, had no requirement for cofactors, and followed simple Michaelis-Menten kinetics with a KM of 115 microM +/- 23 (N = 3). Using inhibitors of xanthine oxidase (allopurinol) and aldehyde oxidase (menadione and isovanillin), the relative roles of these enzymes in this process were determined. At a concentration of BRL 42359 that reflected plasma concentrations observed in humans (4 microM), both menadione (IC50 7 microM) and isovanillin (IC50 15 microM) caused extensive inhibition of the 6-oxidation reaction. In contrast, allopurinol caused no significant inhibition, confirming earlier in vivo work. At higher substrate concentrations (50 and 200 microM), the results with these inhibitors were broadly similar. These results provide strong evidence that aldehyde oxidase and not xanthine oxidase is responsible for the 6-oxidation of BRL 42359 to penciclovir in human liver cytosol, and this is likely to reflect the in vivo situation.

Topics: 2-Aminopurine; Acyclovir; Aldehyde Oxidase; Aldehyde Oxidoreductases; Allopurinol; Antiviral Agents; Benzaldehydes; Cytosol; Famciclovir; Guanine; Humans; Kinetics; Liver; Oxidation-Reduction; Prodrugs; Vitamin K; Xanthine Oxidase

Penciclovir has potent antiviral activity against varicella-zoster virus (VZV). We have characterized the inhibitory effects of penciclovir and acyclovir on the plaque formation of cell-free VZV and cross-resistance of acyclovir-resistant VZV to penciclovir. The apparent effective concentration for 50% plaque reduction (EC50) of penciclovir determined on the third day was significantly lower than that determined on the fourth or fifth day. The size of plaques was smaller in the presence of penciclovir than in the presence of acyclovir. The effective concentrations for 50% reduction of the number of infected cells per plaque were 1.40 and 5.00 micrograms/ml for penciclovir and acyclovir, respectively. Thus penciclovir suppressed spread of infection within developing plaques more efficiently than acyclovir. Five acyclovir-resistant VZV strains with altered DNA polymerase selected by acyclovir were examined for cross-resistance to penciclovir. They were 11- to 18-fold more resistant to ACV than the parent strain, but only 4- to 5-fold more resistant to PCV. Penciclovir-triphosphate carrying the 3'-hydroxyl group of 2'-deoxyribose might have better affinity to the altered viral DNA polymerase than acyclovir-triphosphate without the 3'-hydroxyl group.

Topics: Acyclovir; Antiviral Agents; Cell Line; Drug Resistance, Microbial; Drug Resistance, Multiple; Guanine; Herpesvirus 3, Human; Humans; Molecular Structure; Time Factors; Viral Plaque Assay

The pharmacokinetic profile of penciclovir was determined after a single 500-mg dose of its oral precursor, famciclovir, in 9 healthy volunteers and in 14 patients with chronic hepatic disease. Plasma and urine samples were analyzed for concentrations of penciclovir and 6-deoxy-penciclovir using a reverse-phase high-performance liquid chromatography (HPLC) method. Famciclovir was not quantifiable in patients with hepatic disease, and 6-deoxy-penciclovir was quantifiable in only a limited number of specimens. The extent of systemic availability of penciclovir, as measured by AUC0-infinity, was similar in patients with hepatic disease and in healthy subjects. In contrast, Cmax was significantly lower (average decrease of 43%) in subjects with hepatic disease relative to healthy normal subjects. Median Tmax for subjects with hepatic disease was significantly increased (by 0.75 hours) compared with subjects with normal liver function. These data suggest a decrease in the rate, but not the extent, of systemic availability of penciclovir in patients with hepatic disease. It should be unnecessary to modify the dose of famciclovir for subjects with compensated hepatic disease and normal renal function.

Topics: 2-Aminopurine; Acyclovir; Administration, Oral; Adolescent; Adult; Biological Availability; Chromatography, High Pressure Liquid; Chronic Disease; Famciclovir; Female; Guanine; Humans; Liver Diseases; Male; Metabolic Clearance Rate; Middle Aged; Prodrugs

Famciclovir has been shown to have potent and selective activity against herpesviruses. The possibility of a pharmacokinetic interaction between the anti-viral agent, famciclovir and allopurinol has been investigated in twelve healthy male volunteers following a single oral dose of famciclovir (500 mg) in the presence and absence of steady-state levels of allopurinol (300 mg). Similarly, the pharmacokinetic profiles of allopurinol and oxypurinol prior to and following a single dose of famciclovir were compared. Mean values of Cmax, AUC and terminal-phase half-life for penciclovir following administration of famciclovir alone at 3.3 micrograms.ml-1, 8.8 micrograms.h.ml-1 and 2.1 h, respectively were unchanged by co-administration of allopurinol. Similarly, mean urinary recovery and renal clearance values of penciclovir following famciclovir alone were 56.8% and 27 l.h-1, and when given with allopurinol 59.7% and 27.5 l.h-1, respectively. No evidence of accumulation of the inactive precursor to penciclovir, BRL 42359, was noted as a result of co-administration of the two drugs. Mean steady-state Cmax, AUC and terminal-phase half-life values for allopurinol after co-administration of allopurinol with famciclovir also appeared unchanged from values obtained after dosing of allopurinol alone, at 2.12 micrograms.ml-1, 5.73 micrograms.h.ml-1 and 1.38 h, respectively. Mean Cmax and AUC values of the active metabolite of allopurinol, oxypurinol were 11.2 micrograms.ml-1 and 96.0 micrograms.h.ml-1, respectively, and these were also unaltered by co-administration of famciclovir with allopurinol, with values of 10.6 micrograms/ml and 89.8 micrograms.h/ml, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: 2-Aminopurine; Acyclovir; Administration, Oral; Adult; Allopurinol; Antiviral Agents; Drug Interactions; Famciclovir; Guanine; Half-Life; Humans; Male; Middle Aged; Oxypurinol

Detection of hepadnaviral DNA in extrahepatic tissues of human and animal models of hepatitis B virus (HBV) has raised the question of whether virus replication in organs other than the liver could be targeted for the treatment of chronic hepatitis B. Since duck hepatitis B virus (DHBV) replication is dynamic in the liver, kidney, pancreas, and spleen of newly hatched ducklings infected in ovo, we used the duck model and the new antiherpesvirus agent, famciclovir (FCV), to determine whether antiviral effect of nucleoside analogues on DHBV replication is pluripotential. Day-old ducklings hatched from eggs laid by a DHBV-carrier duck were bled and administered FCV (25 mg/kg/bd) orally for periods of 1, 2, 3, 6, 9, and 12 days. Seventeen (17) hours after the last dose of each regimen the duckling(s) was bled and postmortem samples of liver, kidney, pancreas, and spleen were snap-frozen and stored at -70 degrees C. Analysis of plasma samples of ducklings treated for 2 days and longer by dot-blot hybridisation showed that levels of DHBV DNA were reduced significantly compared to levels in samples collected before treatment begun. Southern blot hybridisation of tissue DNA corroborated these results and showed that DHBV DNA replicative intermediates in all the tissues examined were reduced to levels that reflected the amount of virus released into the blood of each treated duckling. It is concluded from these results that if antiviral agents could be transformed to active metabolites in any infected tissues including the liver, replication of hepadnaviruses would be inhibited.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: 2-Aminopurine; Acyclovir; Administration, Oral; Animals; Animals, Newborn; Antiviral Agents; Biotransformation; Disease Models, Animal; DNA, Viral; Ducks; Eggs; Famciclovir; Guanine; Hepadnaviridae Infections; Hepatitis B Virus, Duck; Kidney; Liver; Organ Specificity; Pancreas; Poultry Diseases; Prodrugs; Spleen; Viremia; Virus Replication; Xanthine Oxidase

The in vitro antihepadnavirus activities of the purine nucleoside analogs ganciclovir (9-[2-hydroxy-1-(hydroxymethyl)ethoxymethyl]guanine) and penciclovir [9-(4-hydroxy-3-hydroxymethylbut-1-yl)guanine; BRL 39123] were compared in primary duck hepatocyte cultures congenitally infected with the duck hepatitis B virus (DHBV). Both compounds inhibited DHBV DNA replication to a comparable extent during continuous short-term treatment of the cultures. However penciclovir was more active both during longer-term continuous treatment (50% inhibitory concentrations: penciclovir, 0.7 +/- 0.1 microM; ganciclovir, 4.0 +/- 0.2 microM) and in washout experiments (50% inhibitory concentrations: penciclovir, 3.0 +/- 0.4 microM; ganciclovir, 46 +/- 1.5 microM) designed to compare the persistence of inhibitory activity after removal of the extracellular compound. The effects on viral protein synthesis were similar to the effects on viral DNA replication. These data suggest that penciclovir or its oral form, famciclovir, may have clinical utility in the treatment of chronic hepatitis B virus infection.

Topics: Acyclovir; Animals; Antiviral Agents; Cell Survival; Cells, Cultured; DNA, Viral; Ducks; Ganciclovir; Guanine; Hepatitis B Virus, Duck; Liver; Viral Proteins

We tested 23 clinical isolates of acyclovir-susceptible, acyclovir-resistant, and foscarnet-resistant herpes simplex virus for susceptibility to penciclovir. Isolates showed cross-resistance to penciclovir and acyclovir, but penciclovir retained a relative activity against foscarnet-resistant isolates. Its clinical utility for the treatment of resistant herpes simplex virus infections remains to be studied.

Topics: Acyclovir; Antiviral Agents; DNA-Directed DNA Polymerase; Drug Resistance, Microbial; Foscarnet; Guanine; Half-Life; Humans; Microbial Sensitivity Tests; Mutation; Simplexvirus; Thymidine Kinase

Famciclovir is the oral form of the potent antiherpesvirus agent, penciclovir. Hydrolysis of one of the acetyl ester groups of famciclovir creates a chiral centre leading to the possible formation of (R)- and (S)-enantiomers. During its conversion to penciclovir, famciclovir forms two chiral metabolites, namely monoacetyl-6-deoxy-penciclovir and monoacetyl-penciclovir. The absolute configuration and stereospecificity of the monoacetyl metabolites of famciclovir, produced in human intestinal wall extract, were determined using isotopically chiral famciclovir and 13C NMR spectroscopy of the isolated metabolites. 13C NMR showed that the esterase(s), in human intestinal wall extract, hydrolysed the acetyl group preferentially from the pro-(S)-acetoxymethyl group of famciclovir. The specificity of esterase action in forming monoacetyl-6-deoxy-penciclovir and monoacetyl-penciclovir was about 77 and 72%, respectively.

Topics: 2-Aminopurine; Acetylation; Acyclovir; Antiviral Agents; Biotransformation; Carbon Isotopes; Famciclovir; Guanine; Humans; In Vitro Techniques; Intestine, Small; Magnetic Resonance Spectroscopy; Prodrugs; Stereoisomerism; Tissue Extracts

Penciclovir is a potent antiherpesvirus agent which is highly selective due to its phosphorylation only in virus infected cells. Phosphorylation of one of the hydroxymethyl groups of penciclovir (PCV) creates a chiral centre leading to the possible formation of (R)- and (S)-enantiomers. The absolute configuration and stereospecificity of the PCV-phosphates produced in cells infected with herpes simplex viruses types 1 and 2 (HSV-1 and HSV-2), as well as by HSV-1-encoded thymidine kinase, were determined using isotopically chiral [4'-13C]PCV precursors and 13C NMR spectroscopy of the isolated metabolites. The absolute configuration of penciclovir-triphosphate (PCV-TP) produced in HSV-1 infected cells was shown to be S with an enantiomeric purity of greater than 95%. However, in contrast fo HSV-1-infected cells in which none of the (R) enantiomer was detected, about 10% of (R)-PCV-TP was produced in HSV-2-infected cells. Phosphorylation of PCV by HSV-1-encoded thymidine kinase was found to give 75% (S)- and 25% (R)-PCV-monophosphate. The proportion of the (S)-isomer appears to be amplified in the subsequent phosphorylations leading to the triphosphate.

Topics: Acyclovir; Carbon Radioisotopes; Cell Line; Esters; Guanine; Herpesvirus 1, Human; Herpesvirus 2, Human; Magnetic Resonance Spectroscopy; Stereoisomerism; Thymidine Kinase

Patients with AIDS often experience recurrent infections with varicella-zoster virus (VZV) requiring repeated or prolonged treatment with acyclovir (ACV), which may lead to the development of ACV resistance. The ACV resistance of isolates recovered from such patients is associated with diminished VZV thymidine kinase (TK) function. We determined the nucleotide sequences of the TK genes of 12 ACV-resistant VZV strains purified from nine patients with AIDS. Five VZV strains contained nucleotide deletions in their TK genes, introducing a premature termination codon which is expected to result in the production of a truncated protein. No detectable full-length TK protein could be immunoprecipitated from extracts of cells infected with these virus strains. These TK-deficient strains were cross resistant to the TK-dependent antiviral agents ACV, 9-(4-hydroxy-3-hydroxymethylbutyl-yl)guanine (penciclovir), and 1-beta-D-arabinofuranosyl-E-5-(2-bromovinyl) uracil (BVaraU). The remaining seven strains each contained a nucleotide change that resulted in an amino acid substitution in the TK protein. These substitutions occurred throughout the TK protein, namely, in the ATP-binding site, the nucleoside-binding site, between the two binding sites, and at the carboxy terminus of the protein. We determined the effects of these mutations on the stability of TK protein expression in virus-infected cells and on the sensitivity of mutants to the TK-dependent antiviral agents ACV, BVaraU, and penciclovir.

Topics: Acquired Immunodeficiency Syndrome; Acyclovir; AIDS-Related Opportunistic Infections; Amino Acid Sequence; Antiviral Agents; Arabinofuranosyluracil; Base Sequence; Drug Resistance, Microbial; Genes, Viral; Genetic Variation; Guanine; Herpesviridae Infections; Herpesvirus 3, Human; Humans; Molecular Sequence Data; Mutagenesis; Precipitin Tests; Sequence Analysis; Sequence Homology, Amino Acid; Thymidine Kinase; Viral Plaque Assay

Penciclovir [PCV; 9-(4-hydroxy-3-hydroxymethylbut-1-yl)guanine; BRL 39123] is a potent and selective inhibitor of herpes simplex virus and varicella-zoster virus in human cell culture. We have compared the activities of PCV and acyclovir (ACV) in DBA/2 mice infected intraperitoneally with herpes simplex virus type 1 SC16 by measuring the amount of virus in peritoneal washings. In untreated mice after an eclipse phase, virus titers are maximum at 48 h after infection and decline thereafter. PCV and ACV reduced virus replication to a similar extent when given ad libitum in drinking water, even though ACV had better oral bioavailability and greater potency in murine cells. Thus, PCV was more active than had been predicted. In dose-response experiments, PCV given as a single subcutaneous dose 24 h after infection was active at a 10-fold-lower dose than ACV (P < 0.01). A single subcutaneous dose of PCV at 5 h after infection prevented virus replication for 3 days and was more effective than three doses of ACV given 1, 5, and 20 h after infection (P < 0.05). The superior activity of PCV following discrete dosing is not due to pharmacokinetic differences but is probably a reflection of the known stability of the intracellular triphosphate. In this model, the maintenance of high concentrations in blood is less important for PCV than for ACV and may lead to less-frequent doses in clinical use.

Topics: Acyclovir; Administration, Oral; Animals; Antiviral Agents; Biological Availability; Dose-Response Relationship, Drug; Female; Guanine; Herpes Simplex; Injections, Intraperitoneal; Injections, Subcutaneous; Mice; Mice, Inbred BALB C; Mice, Inbred DBA; Simplexvirus; Viral Plaque Assay; Virus Replication

(-)-9-[4-Hydroxy-2-(hydroxymethyl)butyl]guanine was evaluated for its efficacy in African green monkeys infected with simian varicella virus. Treatment by intramuscular injection was initiated 48 h after virus inoculation and was continued for 10 days; the treatment showed therapeutic effects on rash and viremia at dosages down to 1 mg/kg of body weight per day.

Topics: Acyclovir; Animals; Antiviral Agents; Chlorocebus aethiops; Dose-Response Relationship, Drug; Guanine; Herpesviridae; Herpesviridae Infections

Penciclovir (PCV) and acyclovir are acyclic guanine analogs which inhibit herpes simplex virus (HSV) DNA polymerase. Their 50% infective doses were 0.5 to 0.8 microgram/ml for clinical isolates of HSV-1 and 1.3 to 2.2 micrograms/ml for HSV-2. Furthermore, HSV-infected cultures receiving 2-h pulses of PCV had 2- to 50-fold less HSV than acyclovir-treated cultures, consistent with the prolonged intracellular half-life of PCV triphosphate.

Topics: Acyclovir; Antiviral Agents; DNA-Directed DNA Polymerase; Guanine; Half-Life; Humans; Simplexvirus

Equine herpesvirus type 1 (EHV-1) was sensitive to the nucleoside analogue penciclovir (PCV) when tested in tissue culture; the ED50 was 1.6 micrograms/ml. Drug-resistant mutants were selected which were found to be TK-defective and approx. 45-fold less sensitive to PCV compared with the parental strain. PCV was compared with the phosphonyl derivative, HPMPA in mice infected with EHV-1. Both drugs were shown to be effective in vivo, limiting wild-type virus replication in respiratory tissues, and reducing viraemia. The treated mice also showed less clinical signs and reduced histopathology compared with placebo-treated controls. The establishment of latent EHV-1 in the mice, however, was not prevented. The results obtained with mice suggest that antiviral chemotherapy may be practical in the horse and that this possibility is worthy of further investigation in the natural host.

Topics: Acyclovir; Adenine; Animals; Antiviral Agents; Cell Line; Drug Resistance, Microbial; Female; Guanine; Herpesviridae Infections; Herpesvirus 1, Equid; Lung; Mice; Mice, Inbred BALB C; Mutation; Organophosphonates; Organophosphorus Compounds; Rabbits; Thymidine Kinase

The metabolism and mode of action of penciclovir [9-(4-hydroxy-3-hydroxymethylbut-1-yl)guanine; BRL 39123] were studied and compared with those of acyclovir. In uninfected MRC-5 cells, low concentrations of the triphosphates of penciclovir and acyclovir were occasionally just detectable, the limit of detection being about 1 pmol/10(6) cells. In contrast, in cells infected with either herpes simplex virus type 2 (HSV-2) or varicella-zoster virus (VZV), penciclovir was phosphorylated quickly to give high concentrations of the triphosphate ester. Following the removal of penciclovir from the culture medium, penciclovir-triphosphate remained trapped within the cells for a long time (half-lives, 20 and 7 h in HSV-2- and VZV-infected cells, respectively). In HSV-2-infected cells, acyclovir was phosphorylated to a lesser extent and the half-life of the triphosphate ester was only 1 h. We were unable to detect any phosphates of acyclovir in VZV-infected cells. (S)-Penciclovir-triphosphate inhibited HSV-1 and HSV-2 DNA polymerase competitively with dGTP, the Ki values being 8.5 and 5.8 microM, respectively, whereas for acyclovir-triphosphate, the Ki value was 0.07 microM for the two enzymes. Both compounds had relatively low levels of activity against the cellular DNA polymerase alpha, with Ki values of 175 and 3.8 microM, respectively. (S)-Penciclovir-triphosphate did inhibit DNA synthesis by HSV-2 DNA polymerase with a defined template-primer, although it was not an obligate chain terminator like acyclovir-triphosphate. These results provide a biochemical rationale for the highly selective and effective inhibition of HSV-2 and VZV DNA synthesis by penciclovir and for the greater activity of penciclovir than that of acyclovir when HSV-2-infected cells were treated for a short time.

Topics: Acyclovir; Base Sequence; Cell Line; DNA-Directed DNA Polymerase; DNA, Viral; Esterification; Guanine; Herpes Simplex; Herpes Zoster; Herpesvirus 3, Human; Humans; Molecular Sequence Data; Nucleic Acid Hybridization; Nucleic Acid Synthesis Inhibitors; Phosphates; Phosphorylation; Simplexvirus; Time Factors

The tolerance to and pharmacokinetics of intravenously administered penciclovir (BRL 39,123A), a novel anti-herpes agent, were investigated in 15 healthy male subjects. The volunteers were divided into three groups, receiving either 10, 15 or 20 mg/kg penciclovir by a 60 min constant-rate infusion. Blood samples were taken sequentially up to 48 h after the start of the infusion and urine collections made at appropriate intervals up to 72 h. After a simple solid phase extraction, concentrations of penciclovir in plasma and urine were determined using HPLC with U.V. detection. Mean values of Cmax, corresponding usually with the end of infusion, and of AUC appeared to increase proportionately with dose. Furthermore, there was no evidence that dose significantly affected any individual pharmacokinetic parameter. Penciclovir was distributed into tissues with an overall mean volume of distribution of approximately 1.5 l.kg-1, i.e. approximately double that of body water. It was rapidly eliminated, with a mean total plasma clearance of 39.3 l.h-1, and a mean terminal-phase half-life of 2.0 h. The majority of the dose, approximately 70%, was excreted unchanged in the urine. Mean renal clearance of BRL 39,123 was 28.1 l.h-1, which exceeds normal glomerular filtration rate and approaches renal plasma flow. At all dose-levels, the infusions of penciclovir were well tolerated, with no evidence of drug-related adverse events.

Topics: Acyclovir; Adult; Antiviral Agents; Dose-Response Relationship, Drug; Guanine; Humans; Infusions, Intravenous; Male; Reference Values; Simplexvirus

The metabolism and mode of action of 9-(4-hydroxy-3-hydroxymethylbut-1-yl)guanine (BRL 39123) were studied in herpes simplex virus type 1 (HSV-1)-infected and uninfected MRC-5 cells and compared with those of acyclovir. In uninfected cells incubated with 10 microM acyclonucleoside for 4 h, no phosphorylation of either BRL 39123 or acyclovir was detected. In contrast, in HSV-1-infected cells, both BRL 39123 and acyclovir were phosphorylated up to the triphosphate esters. Phosphorylation of BRL 39123 occurred much more rapidly and proceeded to a greater extent than did that of acyclovir. Furthermore, following the removal of acyclonucleoside from the culture medium, the intracellular triphosphate ester of BRL 39123 was much more stable than was that of acyclovir, the half-lives being about 10 and 0.7 h, respectively. BRL 39123 treatment effectively inhibited the formation of HSV-1 DNA in infected MRC-5 cells, 50% inhibitory concentrations of BRL 39123 and acyclovir being 0.04 microgram/ml (0.16 microM) and 0.15 microgram/ml (0.67 microM), respectively. In addition, BRL 39123 was shown to be more effective than acyclovir at inhibiting viral DNA synthesis following short treatment times, presumably reflecting the greater stability of BRL 39123 triphosphate. Neither BRL 39123 nor acyclovir inhibited cellular DNA synthesis in uninfected cells at concentrations of up to 100 micrograms/ml.

Topics: Acyclovir; Antiviral Agents; Cells, Cultured; Chromatography, High Pressure Liquid; DNA, Viral; Guanine; Humans; Phosphorylation; Simplexvirus

Topics: Acyclovir; Bromodeoxyuridine; Chemical Phenomena; Chemistry; Ganciclovir; Guanine; Guanosine Triphosphate; Herpesviridae Infections; Humans

The limited oral absorption in rodents of the antiherpesvirus agent 9-(4-hydroxy-3-hydroxymethylbut-l-yl)guanine (BRL 39123 [penciclovir; British approved name]) prompted a search for oral prodrugs. The 6-deoxy derivative of penciclovir (BRL 42359) and the corresponding diacetyl and dipropionyl 6-deoxy derivatives (BRL 42810 [famciclovir; British approved name] and BRL 43599) were tested as oral prodrugs. The in vivo absorption (dose, 0.2 mmol/kg) and the conversion to the active compound, penciclovir, were determined in rats. Compared with the sodium salt of penciclovir given intravenously, the bioavailabilities of penciclovir from orally administered penciclovir, BRL 42359, famciclovir, and BRL 43599 were 1.5, 9, 41, and 27%, respectively. These prodrugs and 6-deoxyacyclovir were tested for stability in rat duodenal contents and for metabolism in rat intestinal wall homogenate, liver homogenate, and blood and in the corresponding human fluids and tissues. Famciclovir was much more stable than BRL 43599 in human duodenal contents (half-lives, greater than 2 h and 7 min, respectively) yet was efficiently converted to penciclovir by the tissue homogenates. The major metabolic pathway was by deacetylation followed by oxidation at the 6 position. The rate of oxidation was comparable to that of 6-deoxyacyclovir, which is known to be converted efficiently to acyclovir in humans. Famciclovir was selected for further evaluation and progression to studies in humans. These subsequent studies confirmed that, after oral dosing with famciclovir, more than half the dose was absorbed and rapidly converted to penciclovir.

Topics: 2-Aminopurine; Acyclovir; Adenine; Animals; Antiviral Agents; Bile; Biological Availability; Chromatography, High Pressure Liquid; Duodenum; Famciclovir; Guanine; Humans; In Vitro Techniques; Intestinal Mucosa; Liver; Male; Prodrugs; Rats; Tissue Distribution

A rapid, sensitive and reliable reversed-phase high-performance liquid chromatographic (HPLC) method with UV detection has been developed for the assay of a novel anti-herpes agent, 9-(4-hydroxy-3-hydroxymethylbut-1-yl)guanine (BRL-39123), in human plasma and urine. The drug and the internal standard, the structural analogue BRL-42377, were extracted from the biological matrix by adsorption on a cation-exchange column and were subsequently eluted under alkaline conditions prior to HPLC. The method is reproducible, with coefficients of variation of ca. 5%, and linear from 0.1 to at least 30 micrograms ml-1 in plasma and from 50 to at least 2000 micrograms ml-1 in urine. The method has been used extensively to measure BRL-39123 in plasma and urine samples generated during clinical studies and is adequate for defining pharmacokinetics at projected therapeutic doses.

Topics: Acyclovir; Antiviral Agents; Chromatography, High Pressure Liquid; Guanine; Humans

Potential oral prodrugs of the antiherpesvirus acyclonucleoside 9-[4-hydroxy-3-(hydroxymethyl)but-1-yl]guanine (1, BRL 39123) have been synthesized and evaluated for bioavailability of 1 in the blood of mice. Reduction of 9-[4-acetoxy-3-(acetoxymethyl)but-1-yl]-2-amino-6-chloropurine (13) using ammonium formate and 10% palladium on carbon afforded the 2-aminopurine 14, which was hydrolyzed to the monoacetate 15 and to 2-amino-9-[4-hydroxy-3-(hydroxymethyl)but-1-yl]purine (5). The 2-aminopurine 5 was subsequently converted to additional monoester (17, 21-23) and diester (16, 24) derivatives and to its di-O-isopropylidene derivative 18. Both 5 and its esters (14-17, 21, 22) and also 18 were well absorbed after oral administration and converted efficiently to 1, the diacetyl (14) and dipropionyl (16) esters providing concentrations of 1 in the blood that were more than 15-fold higher than those observed after dosing either 1 or its esters (25-27). Some 6-alkoxy-9-[4-hydroxy-3-(hydroxymethyl)but-1-yl]purines (8-10), the preparation of which has been reported previously, also showed improved absorption properties, but their conversion to 1 was less efficient than for the 2-aminopurine derivatives. On the basis of these results and subsequent experiments involving determinations of rates of conversion to 1 in the presence of rat and human tissue preparations, 9-[4-acetoxy-3-(acetoxymethyl)but-1-yl]-2-aminopurine (14, BRL 42810) was identified as the preferred prodrug of 1. Oral bioavailability studies in healthy human subjects confirmed 14 as an effective prodrug, and this compound is now being evaluated in clinical trials.

Topics: 2-Aminopurine; Acyclovir; Adenine; Animals; Antiviral Agents; Chemical Phenomena; Chemistry; Famciclovir; Guanine; Intestinal Absorption; Mice; Prodrugs

The antiviral activity of 9-(4-hydroxy-3-hydroxymethylbut-1-yl)guanine (BRL 39123) was assessed in several animal models of herpes simplex virus (HSV) infection. BRL 39123 was as active as acyclovir (ACV) when applied topically to guinea pigs with a cutaneous HSV type 1 (HSV-1) infection and was also active topically in an HSV-2 genital infection. Before systemic administration to infected animals, BRL 39123 and ACV were administered orally and subcutaneously to mice, and the blood was assayed for each compound by high-pressure liquid chromatography. When given systemically to mice infected cutaneously with HSV-1, BRL 39123 was as active as ACV. In mice infected intranasally with HSV-1 or HSV-2, single daily subcutaneous doses of BRL 39123 were more effective than equivalent treatment with ACV, reflecting the more persistent activity seen in cell culture and a more stable triphosphate within the infected cell. When the compounds were supplied in drinking water for this infection, BRL 39123 and ACV had similar potencies against HSV-1, although ACV was more active against an HSV-2 infection than BRL 39123 was. In mice infected intraperitoneally with HSV-1, BRL 39123 was 10-fold more potent than ACV and a single dose of BRL 39123 reduced virus replication within the peritoneal cavity more effectively than 3 doses of ACV given 1, 5, and 20 h after infection. Although BRL 39123 failed to eradicate the virus from mice latently infected with HSV-1, treatment initiated 5 h after infection of the ear pinna reduced the numbers of mice that developed latent infections.

Topics: Acyclovir; Animals; Antiviral Agents; Biological Availability; Chromatography, High Pressure Liquid; Female; Guanine; Guinea Pigs; Herpes Simplex; Mice; Mice, Inbred BALB C; Mice, Inbred DBA; Mice, Nude; Peritoneal Diseases; Skin Diseases, Infectious

The activity of 9-(4-hydroxy-3-hydroxymethylbut-1-yl)guanine (BRL 39123) against several herpesviruses was compared with that of acyclovir (ACV). In plaque reduction tests with clinical isolates of herpes simplex virus type 1 (HSV-1), herpes simplex virus type 2 (HSV-2), and varicella-zoster virus, mean 50% inhibitory concentrations (IC50S) (n = number tested) for BRL 39123 were 0.4 (n = 17), 1.5 (n = 13), and 3.1 (n = 5) micrograms/ml, respectively. Corresponding IC50S for ACV were 0.2, 0.6, and 3.8 micrograms/ml. Cytomegalovirus was relatively resistant to BRL 39123 (IC50, 51 micrograms/ml), but equid herpesvirus 1, bovid herpesvirus 2, and felid herpesvirus 1 were susceptible (IC50S, 1.6, 1.2, and 0.9 micrograms/ml, respectively). BRL 39123 was inactive against an HSV-1 strain which does not express thymidine kinase activity, but a DNA polymerase mutant selected for resistance to ACV was sensitive to BRL 39123 (IC50, 1.5 micrograms/ml). In contrast to the results from plaque reduction tests, BRL 39123 was more active than ACV against HSV-1 and of equal activity against HSV-2 in virus yield reduction assays in MRC-5 cells. After treatment of HSV-infected cultures for short periods, BRL 39123 was considerably more effective than ACV at reducing virus replication, and furthermore, after removal of extracellular BRL 39123, virus replication remained depressed for long periods, whereas such persistent activity was not observed with ACV. Neither compound significantly affected MRC-5 cell replication at 100 micrograms/ml, but at 300 micrograms/ml BRL 39123 was more inhibitory than ACV.

Topics: Acyclovir; Antiviral Agents; Cells, Cultured; Cytopathogenic Effect, Viral; Drug Resistance, Microbial; Guanine; Herpesviridae; Viral Plaque Assay; Virus Replication