USC-087 protects Syrian hamsters against lethal challenge with human species C adenoviruses.

Human adenoviruses (AdV) cause generally mild infections of the respiratory and GI tracts as well as some other tissues. However, AdV can cause serious infection in severely immunosuppressed individuals, especially pediatric patients undergoing allogeneic hematopoietic stem cell transplantation, where mortality rates are up to 80% with disseminated disease. Despite the seriousness of AdV disease, there are no drugs approved specifically to treat AdV infections. We report here that USC-087, an N-alkyl tyrosinamide phosphonate ester prodrug of HPMPA, the adenine analog of cidofovir, is highly effective against multiple AdV types in cell culture. USC-087 is also effective against AdV-C6 in our immunosuppressed permissive Syrian hamster model. In this model, hamsters are immunosuppressed by treatment with high dose cyclophosphamide. Injection of AdV-C6 (or AdV-C5) intravenously leads to a disseminated infection that resembles the disease seen in humans, including death. We have tested the efficacy of orally-administered USC-087 against the median lethal dose of intravenously administered AdV-C6. USC-087 completely prevented or significantly decreased mortality when administered up to 4 days post challenge. USC-087 also prevented or significantly decreased liver damage caused by AdV-C6 infection, and suppressed virus replication even when administered 4 days post challenge. These results imply that USC-087 is a promising candidate for drug development against HAdV infections.

Synthesis and antiviral activities of methylenecyclopropane analogs with 6-alkoxy and 6-alkylthio substitutions that exhibit broad-spectrum antiviral activity against human herpesviruses.

Methylenecyclopropane nucleosides have been reported to be active against many of the human herpesviruses. The most active compound of this class is cyclopropavir (CPV), which exhibits good antiviral activity against human cytomegalovirus (HCMV), Epstein-Barr virus, both variants of human herpesvirus 6, and human herpesvirus 8. CPV has two hydroxymethyl groups on the methylenecyclopropane ring, but analogs with a single hydroxymethyl group, such as the prototypical (S)-synguanol, are also active and exhibit a broader spectrum of antiviral activity that also includes hepatitis B virus and human immunodeficiency virus. Here, a large set of monohydroxymethyl compounds with ether and thioether substituents at the 6 position of the purine was synthesized and evaluated for antiviral activity against a range of human herpesviruses. Some of these analogs had a broader spectrum of antiviral activity than CPV, in that they also inhibited the replication of herpes simplex viruses 1 and 2 and varicella-zoster virus. Interestingly, the antiviral activity of these compounds appeared to be dependent on the activity of the HCMV UL97 kinase but was relatively unaffected by the absence of thymidine kinase activity in HSV. These data taken together indicate that the mechanism of action of these analogs is distinct from that of CPV. They also suggest that they might be useful as broad-spectrum antiherpesvirus agents and may be effective in the treatment of resistant virus infections.