Efficacy of the acyclic guanosine analog buciclovir [(R)-9-(3,4-dihydroxybutyl)guanine] in experimental genital herpes

Electrochemical Enantioselective Dihydroxylation Reaction of N-Alkenyl Nucleobases for the Construction of Chiral Acyclic Nucleosides

A simple and sustainable KI-mediated electrochemical enantioselective dihydroxylation reaction of N-alkenyl nucleobases was developed for the first time in an undivided cell. A series of chiral acyclic nucleosides bearing two...

Synthesis of Chiral Acyclic Nucleosides by Sharpless Asymmetric Dihydroxylation: Access to Cidofovir and Buciclovir

An efficient method to construct chiral acyclic nucleosides via Sharpless asymmetric dihydroxylation of N-allylpyrimidines or N-alkenylpurines is reported. A range of chiral acyclic nucleosides with two adjacent hydroxyl groups present on the side chains could be produced in good yields (up to 97% yield) and excellent enantioselectivities (90-99% ee). The synthetic utility of the reaction was demonstrated by the catalytic asymmetric synthesis of ( S)-Cidofovir and ( R)-Buciclovir.

Promising new antiviral drugs

We now have a basis for a more rational approach to rapid evaluation and development of antiviral drugs by screening for activity in vitro, testing for toxicity and efficacy in animals, and clinical testing in humans. Acyclovir is a prototype of this improved process. Interferon has a beneficial effect against CMV infection in renal transplant patients and has promising results in the treatment of papillomas and rhinovirus infections. It does not seem to be as effective against genital herpes or varicella zoster as acyclovir. Ribavirin is effective against respiratory syncytial virus infections and Lassa fever. Varicella-zoster virus is highly sensitive to bromovinyl deoxyuridine in vitro. Phosphonoformate is effective in herpes simplex in animals but of little clinical benefit topically in human recurrent A2 herpes. Zidovudine may decrease mortality rates and infectious complications in patients with acquired immunodeficiency syndrome. DHPG (9-(1,3-dihydroxy-2-propoxymethyl]guanine is useful in treatment of cytomegalovirus and infection in immunocompromised patients. The prodrug of acyclovir results in high blood levels of acyclovir and shows promise in the treatment of varicella-zoster infections. Many halogenated pyrimidine nucleoside analogs are being developed. Buciclovir is another acyclic guanosine analog effective against herpes simplex virus in vitro. 2'-nor-cyclic guanosine monophosphate has a broad antiviral spectrum of action. Interleukin-2 is being investigated. Combined therapies of two or more antiviral drugs or antiviral drugs and other treatments are being studied.

Critical determinants of antiherpes efficacy of buciclovir and related acyclic guanosine analogs

Buciclovir is an example of an antiherpes, acyclic guanosine analog activated by the viral thymidine kinase and inhibiting viral DNA synthesis in infected cells. An investigation of closely related buciclovir-analogs with similar antiherpes activities in cell cultures and similar, or identical, modes of action but with disparate effects in vivo, revealed the following critical determinants of antiherpes efficacy. (1) The accumulation of guanosine analog-triphosphates in infected cells, which is cell-type-specific and analog-dependent. (2) The potencies of the triphosphates as inhibitors of the viral DNA polymerase. (3) The plasma kinetics of the analogs, which are widely different despite the similar structures. (4) The penetration into nervous tissue relative to penetration into non-nervous tissues, of importance in connection with the neurotropic behavior of the virus. (5) The concentration of the antagonist thymidine in certain tissues. (6) The difference in pathogenesis between primary infections and recurrent infections, exemplified in the different efficacies of topically applied drugs in cutaneous and genital HSV-2 infections in guinea pigs.