acyclovir and acyclovir-monophosphate

Acyclovir, 9-(2-hydroxyethoxymethyl)guanine, is an acyclic nucleoside analogue which has a high activity and selectivity for herpes viruses, particularly herpes simplex viruses types 1 and 2 and varicella zoster virus. This selectivity is due to the initial activation of the drug by phosphorylation by a herpes virus-specified thymidine kinase. Normal cellular enzymes do not phosphorylate acyclovir to any significant degree. Acyclovir monophosphate is subsequently converted to a triphosphate which is a more potent inhibitor of herpes virus DNA polymerases than of cellular DNA polymerases. The relationship between the amount of acyclovir triphosphate formed and its inhibition constant (Ki) for the particular viral or cellular DNA polymerase is predictive of the inhibitory activity of acyclovir on DNA replication.

Topics: Acyclovir; DNA Polymerase II; DNA Replication; DNA, Viral; Herpesvirus 3, Human; Peptide Chain Termination, Translational; Phosphorylation; Simplexvirus; Thymidine Kinase

Acyclovir, an acrylic purine nucleoside analog, is a highly potent inhibitor of herpes simplex virus (HSV), types 1 and 2, and varicella zoster virus, and has extremely low toxicity for the normal host cells. This selectivity is due to the ability of these viruses to code for a viral thymidine kinase capable of phosphorylating acyclovir to a monophosphate; this capability is essentially absent in uninfected cells. The acyclovir monophosphate (acyclo-GMP) is subsequently converted to acyclovir triphosphate (acyclo-GTP) by cellular enzymes. Acyclo-GTP persists in HSV-infected cells for many hours after acyclovir is removed from the medium. The amounts of acyclo-GTP formed in HSV-infected cells are 40 to 100 times greater than in uninfected Vero cells. Acyclo-GTP acts as a more potent inhibitor of the viral DNA polymerases than of the cellular polymerases. The DNA polymerases of HSV-1 and HSV-2 also use acyclo-GTP as a substrate and incorporate acyclo-GMP into the DNA primer-template to a much greater extent than do the cellular enzymes. The viral DNA polymerase binds strongly to the acyclo-GMP-terminated template, and in thereby inactivated.

Topics: Acyclovir; Animals; Antiviral Agents; Cell Line; Guanine; Humans; Nucleic Acid Synthesis Inhibitors; Simplexvirus; Thymidine Kinase

Topics: Acyclovir; Adolescent; Adult; Aged; Child; Clinical Trials as Topic; Double-Blind Method; Female; Guanine; Humans; Keratitis, Dendritic; Male; Middle Aged; Ointments; Vidarabine

Anti-herpes simplex virus (HSV) drug acyclovir (ACV) is phosphorylated by the viral thymidine kinase (TK), but not the cellular TK. Phosphorylated ACV inhibits cellular DNA synthesis and kills the infected cells. We hypothesize that ACV monophosphate (ACVP), which is an activated metabolite of ACV, should be efficient in killing cells independent of HSV-TK. If so, ACVP should be a cytotoxic agent if properly delivered to the cancer cells. The Lipid/Calcium/Phosphate (LCP) nanoparticles (NPs) with a membrane/core structure were used to encapsulate ACVP to facilitate the targeted delivery of ACVP to the tumor. The LCP NPs showed entrapment efficiency of ~70%, the nano-scaled particle size and positive zeta potential. Moreover, ACVP-loaded LCP NPs (A-LCP NPs) exhibited concentration-dependent cytotoxicity against H460 cells and increased S-phase arrest. More importantly, a significant reduction of the tumor volume over 4 days following administration (p<0.05-0.005) of A-LCP NPs, suggests excellent in vivo efficacy. Whereas, two free drugs (ACV and ACVP) and blank LCP NPs showed little or no therapeutic effect. It was also found that the high efficacy of A-LCP NPs was associated with the ability to induce dramatic apoptosis of the tumor cells, as well as significantly inhibit tumor cell proliferation and cell cycle progression. In conclusion, with the help of LCP NPs, monophosphorylation modification of ACV can successfully modify an HSV-TK-dependent antiviral drug into an anti-tumor drug.

Topics: Acyclovir; Animals; Antineoplastic Agents; Antiviral Agents; Calcium Phosphates; Cell Line, Tumor; Cell Survival; Female; Humans; Lipids; Mice; Mice, Nude; Nanoparticles; Neoplasms; Simplexvirus; Thymidine Kinase; Tumor Burden; Viral Proteins; Xenograft Model Antitumor Assays

Incomplete coverage and short duration of action limit the effectiveness of vaginally administered drugs, including microbicides, for preventing sexually transmitted infections. We investigated vaginal distribution, retention, and safety of nanoparticles with surfaces modified to enhance transport through mucus. We show that mucus-penetrating particles (MPPs) provide uniform distribution over the vaginal epithelium, whereas conventional nanoparticles (CPs) that are mucoadhesive are aggregated by mouse vaginal mucus, leading to poor distribution. Moreover, when delivered hypotonically, MPPs were transported advectively (versus diffusively) through mucus deep into vaginal folds (rugae) within minutes. By penetrating into the deepest mucus layers, more MPPs were retained in the vaginal tract after 6 hours compared to CPs. After 24 hours, when delivered in a conventional vaginal gel, patches of a model drug remained on the vaginal epithelium, whereas the epithelium was coated with drug delivered by MPPs. We then developed MPPs composed of acyclovir monophosphate (ACVp). When administered before vaginal herpes simplex virus 2 challenge, ACVp-MPPs protected 53% of mice compared to only 16% protected by soluble drug. Overall, MPPs improved vaginal drug distribution and retention, provided more effective protection against vaginal viral challenge than soluble drug, and were nontoxic when administered daily for 1 week.

Topics: Acyclovir; Administration, Intravaginal; Animals; Female; Humans; Mice; Nanoparticles; Simplexvirus; Vagina

Phosphonoformic acid (PFA, foscarnet) belongs to a class of antiviral drugs that inhibit the human cytomegalovirus DNA polymerase (UL54) by mimicking the pyrophosphate leaving group of the nucleotide transfer reaction. Difficulties expressing UL54 have hampered investigation of the precise structural requirements rendering inhibition by this drug. However, a previously engineered chimeric DNA polymerase, constructed by mutating the homologous polymerase from bacteriophage RB69 (gp43) to express several variable elements from UL54, can bypass this obstacle because of its favorable expression and acquired sensitivity to PFA (Tchesnokov, E. P., Obikhod, A., Schinazi, R. F., and Götte, M. (2008) J. Biol. Chem. 283, 34218-34228). Here, we compare two crystal structures that depict the chimeric DNA polymerase with and without PFA bound. PFA is visualized for the first time in the active site of a DNA polymerase, where interactions are resolved between the PP(i) mimic and two basic residues absolutely conserved in the fingers domain of family B polymerases. PFA also chelates metal ion B, the cation that contacts the triphosphate tail of the incoming nucleotide. These DNA complexes utilize a primer-template pair enzymatically chain-terminated by incorporation of acyclo-GMP, the phosphorylated form of the anti-herpes drug acyclovir. We postulate that the V478W mutation present in the chimera is critical in that it pushes the fingers domain to more readily adopt the closed conformation whether or not the drug is bound. The closed state of the fingers domain traps the variant polymerase in the untranslocated state and increases affinity for PFA. This finding provides a model for the mechanism of UL54 stalling by PFA.

Topics: Acyclovir; Amino Acid Substitution; Crystallography, X-Ray; Cytomegalovirus; DNA-Directed DNA Polymerase; Foscarnet; Humans; Models, Molecular; Point Mutation; Protein Structure, Tertiary; Viral Proteins

The combinational use of acyclovir (ACV) phosphonate esters and alpha(2)-interferon was shown to produce a synergistic effect on inhibition of HSV-1 replication in Vero cell cultures. Unlike other acyclovir phosphonate derivatives studied earlier, ACV H-phosphonate is not an ACV prodrug. On penetrating into the cells, it may be directly converted into ACV monophosphate escaping dephosphonylation-phosphorylation steps.

Topics: Acyclovir; Animals; Antiviral Agents; Chemistry, Pharmaceutical; Chlorocebus aethiops; Chromatography; Drug Design; Herpesviridae; Interferon-alpha; Kinetics; Models, Biological; Organophosphonates; Phosphorylation; Purine-Nucleoside Phosphorylase; Vero Cells

The woodchuck was selected to study the efficacy of liver-targeted antiviral drugs on hepadnavirus replication. Nineteen woodchucks chronically infected with woodchuck hepatitis virus were treated with adenine arabinoside monophosphate or acyclovir monophosphate, either free or conjugated with the liver-targeting molecule lactosaminated human serum albumin. Circulating woodchuck hepatitis virus DNA levels remained unchanged in untreated animals and in those receiving the carrier lactosaminated human serum albumin alone; in contrast, they were consistently lower after 5 days of treatment with the antiviral drugs. Free and conjugated adenine arabinoside monophosphate were active at doses of 10 and 0.75 mg/kg, respectively, and free and coupled ACVMP were active at doses of 20 and 2.6 mg/kg, respectively. These results indicate that the dosages of adenine arabinoside monophosphate and acyclovir monophosphate required to inhibit hepadnavirus growth can be sharply reduced by coupling the drugs to lactosaminated human serum albumin.

Topics: Acyclovir; Animals; DNA, Viral; Dose-Response Relationship, Drug; Drug Carriers; Hepadnaviridae; Hepatitis, Viral, Animal; Humans; Marmota; Serum Albumin; Vidarabine Phosphate; Viremia

The potent inhibition of herpes simplex type 1 (HSV-1) DNA polymerase by acyclovir triphosphate has previously been shown to be due to the formation of a dead-end complex upon binding of the next 2'-deoxynucleoside 5'-triphosphate encoded by the template after incorporation of acyclovir monophosphate into the 3'-end of the primer (Reardon, J. E., and Spector, T. (1989) J. Biol. Chem. 264, 7405-7411). This mechanism of inhibition of HSV-1 DNA polymerase has been used here to design an affinity column for the enzyme. A DNA hook template-primer containing an acyclovir monophosphate residue on the 3'-primer terminus has been synthesized and attached to a resin support. In the absence of added nucleotides, the column behaves as a simple DNA-agarose column, and HSV-1 DNA polymerase can be chromatographed using a salt gradient. The presence of the next required nucleotide encoded by the template (dGTP) increases the affinity of HSV-1 DNA polymerase for the acyclovir monophosphate terminal primer-template attached to the resin, and the enzyme is retained even in the presence of 1 M salt. The enzyme can be eluted from the column with a salt gradient after removal of the nucleotide from the buffer. Traditionally, the affinity purification of an enzyme relies on elution by a salt gradient, pH gradient, or more selectively by addition of a competing ligand (substrate/inhibitor) to the elution buffer. In the present example, elution of HSV-1 polymerase is facilitated by removal of the substrate from the buffer. This represents an example of mechanism-based affinity chromatography.

Topics: Acyclovir; Antiviral Agents; Base Sequence; Chromatography, Affinity; DNA-Directed DNA Polymerase; HeLa Cells; Humans; Kinetics; Molecular Sequence Data; Nucleic Acid Conformation; Nucleic Acid Synthesis Inhibitors; Oligonucleotides; Simplexvirus; Templates, Genetic

The authors report two cases of patients affected by Central Serous Retinopathy (C.S.R.) lasting few days; they were immediately started with an antiviral therapy (Acycloguanosine) for few days and in both cases the regression of symptoms and a flat retina were observed after a very shorter time than the spontaneous course. A fluorescein angiography confirmed a healing of the leaking points very few days after the therapy was discontinued. The authors discuss their finding in relation to the latest hypothesis on C.S.R. pathogenesis.

Topics: Acyclovir; Adult; Fluorescein Angiography; Fundus Oculi; Humans; Male; Retinal Diseases

Topics: Acyclovir; Animals; Drug Carriers; Female; Liver; Magnetic Resonance Spectroscopy; Mice; Serum Albumin; Tissue Distribution; Tritium

D-Galactopyranosyl residues were coupled to poly(L-lysine) and the antiviral agents arabinofuranosyladenine 5'-monophosphate (ara-AMP) and acyclovir were conjugated with this glycosylated polymer. In mice the ara-AMP conjugate accomplished a selective drug delivery to liver cells.

Topics: Acyclovir; Animals; Arabinonucleotides; DNA; Galactose; Liver; Mice; Pharmaceutical Vehicles; Polylysine; Serum Albumin; Vidarabine Phosphate

The thymidine kinase-complex isolated from herpes simplex virus type 1 and type 2 (HSV-1 and HSV-2) is associated with the following enzyme activities:ATP:dThd (dCyd) deoxypyrimidine kinase, ATP:dTMP thymidylate kinase, ADP:dThd- and AMP:dThd 5'-phosphotransferase. In kinetic experiments it is shown that ara-AMP inhibits AMP:dThd- and ADP:dThd phosphotransferase activity, while acyclo-GMP impairs ADP:dThd phosphotransferase reaction only; the inhibition was found to be non-competitive. The functional subunit ATP:dThd kinase was not affected by either compound.

Topics: Acyclovir; Arabinonucleotides; Kinetics; Multienzyme Complexes; Simplexvirus; Thymidine Kinase; Vidarabine Phosphate

The metabolism of acyclovir to its mono-, di-, and triphosphate derivatives was examined in uninfected and virus-infected cells. The level of phosphorylation of acyclovir was dependent upon virus type, cell line, exogenous drug concentration, and exposure time. Acyclovir phosphorylation was inhibited by exogenously added nucleosides. The order of inhibition was deoxythymidine greater than deoxycytidine greater than guanosine greater than or equal to deoxyguanosine. Acyclovir triphosphate persisted in infected cells after removal of the drug from the medium. The initial half-life of the triphosphate was 1.2 h in the absence of the drug in the medium, but triphosphate levels reached a plateau after 6 h. The presence of low concentrations of the drug in the medium resulted in a longer persistence of the intracellular triphosphate and a higher plateau level.

Topics: Acyclovir; Antiviral Agents; Cell Line; Chromatography, High Pressure Liquid; Culture Media; Deoxyribonucleosides; Guanine; Phosphorylation; Simplexvirus; Time Factors

Topics: Acyclovir; Adenosine Diphosphate; Animals; Cell Transformation, Viral; Chlorocebus aethiops; Erythrocytes; Guanine; Guanosine Monophosphate; Guanylate Kinases; Haplorhini; Humans; Kidney; Kinetics; Nucleoside-Phosphate Kinase; Organophosphorus Compounds; Phosphorylation; Phosphotransferases; Simplexvirus