brivudine and edoxudin

Topics: Acyclovir; Adenine; Animals; Antiviral Agents; Arabinonucleosides; Bromodeoxyuridine; Chemical Phenomena; Chemistry; Cytarabine; Deoxyuridine; Guanine; Herpesviridae Infections; Humans; Idoxuridine; Nucleosides; Ribavirin; Thymidine; Virus Diseases; Viruses

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

Using an in vitro system we measured the corneal epithelial cytotoxicity and the antiviral activity of the antiviral agents idoxuridine (IDU), trifluridine (TFT), ethyldeoxyuridine (EDU), and (E)-5-(2-Bromovinyl)-2'-deoxyuridine (BVDU). Confluent rabbit corneal epithelial cell cultures were established, and the antiviral agents were added for 5, 30, or 60 min at a range of concentrations including that used clinically (IDU 0.1%, TFT 1.0%, BVDU 0.1%, EDU 2.0%). Twelve hour [3H]thymidine incorporation then was measured and expressed as % inhibition of control cultures. In separate experiments confluent corneal epithelial cell monolayers were inoculated with 10(4) plaque forming units (PFU) of HSV type 1 (McKrae strain) for 1 h, and IDU 0.1%, TFT 1.0%, and BVDU 0.1% were added to the culture for determination of PFU inhibition. Significant dose-, but not time-dependent, toxicity was observed at the clinical concentrations of IDU, TFT, and EDU. Toxicity was absent for BVDU. TFT and IDU were the most toxic, and EDU was of intermediate toxicity. IDU, TFT, and BVDU showed significant antiviral activity in this corneal epithelial cell culture system (TFT greater than BVDU greater than IDU). The results of this in vitro study paralleled the findings of previous in vivo corneal epithelial toxicity studies of IDU, TFT, and BVDU. Our data, however, suggest that EDU has a potential for clinical toxicity and further studies are recommended. Our model may be useful in the future toxicologic study of new antiviral agents.

Topics: Animals; Antiviral Agents; Bromodeoxyuridine; Cell Survival; Cornea; Deoxyuridine; Epithelium; Idoxuridine; In Vitro Techniques; Rabbits; Thymidine; Trifluridine

In the rat, the highly potent anti-herpes drug (E)-5-(2-bromovinyl)-2'-deoxyuridine (BVdUrd) is rapidly converted to its base (E)-5-(2-bromovinyl)uracil (BVUra) through the action of pyrimidine nucleoside phosphorylases. However, BVdUrd can be regenerated or even generated de novo from BVUra by a pentosyl transfer reaction upon the administration of 2'-deoxythymidine (dThd), 2'-deoxyuridine (dUrd) or 5-ethyl-2'-deoxyuridine (EtdUrd). The antiherpetic drugs EtdUrd and 5-(2-chloroethyl)-2'-deoxyuridine (ClEtdUrd) can also be regenerated or generated de novo from their respective bases 5-ethyluracil (EtUra) and 5-(2-chloroethyl)uracil (ClEtUra), by a pentosyl transfer mediated by the administration of dThd or dUrd as deoxyribosyl donor. The generation or regeneration of BVdUrd, EtdUrd and ClEtdUrd from their bases (BVUra, EtUra and ClEtUra, respectively) is readily achieved because the latter have long half-lifes. Thus, the active anti-herpes drugs can be (re)generated repeatedly after a single administration of these nucleosides or their bases, followed by repeated administrations of dUrd.

Topics: Animals; Antiviral Agents; Bromodeoxyuridine; Bromouracil; Deoxyuridine; Half-Life; Humans; Male; Rabbits; Rats; Rats, Inbred Strains; Simplexvirus; Uracil

Topical antiviral treatments for recurrent infection with herpes simplex virus in immunocompetent patients have been generally ineffective. We investigated whether in vitro drug measures could predict in vivo efficacy. Twelve topical antiviral formulations were evaluated in vitro by measuring inhibition of viral plaque formation in cell culture (ID50) and drug penetration through excised guinea pig skin. In vivo efficacy for each treatment was determined in an experimental cutaneous infection with herpes simplex virus type 1 in guinea pigs and expressed as the percent reduction in lesion number, lesion area, and virus titer in the lesions. The in vitro findings were correlated with the results in the animal model. ID50 was a poor predictor of in vivo efficacy, whereas stronger correlations were found between the degree of skin penetration and in vivo activity. The best correlation was noted by using a summary expression of the in vitro results as follows: the ratio of drug penetration through skin at 37 C to ID50 (r = .95, .94, and .92 for lesion number, area, and virus titer, respectively, P less than .0005). Determination of this in vitro index should be included in the preclinical evaluation of new topical antiviral formulations.

Topics: Acyclovir; Administration, Topical; Animals; Antiviral Agents; Bromodeoxyuridine; Deoxyuridine; Diffusion; Female; Guinea Pigs; Herpes Simplex; Idoxuridine; Pharmaceutical Vehicles; Skin Diseases; Trifluridine; Vidarabine