Retroviruses such as HIV are distinguished from other viruses by two steps in the viral life cycle, reverse transcription of the viral RNA to make a cDNA copy, and integration of that cDNA into a chromosome of the host. The reverse transcription step has been exploited as a target for antiviral agents. Another HIV encoded enzyme, the protease, has also been exploited as an inhibitor target. Inhibitors of these steps, however, have been found to be plagued by viral escape mutants in clinical applications, adding interest to the search for new inhibitors of other targets. The applicants propose to develop inhibitors of the third HIV-encoded enzyme, integrase, a viral function that has not yet been exploited as a target. Previous work has outlined diverse classes of compounds that inhibit purified integrase protein, though none are active against integrase in vivo. The applicants will use combinatorial chemistry to develop well designed and focused libraries of derivatives of reported inhibitors, and test these compounds against integrase in vitro. With this approach, the applicants will also identify new classes of inhibitors, and they will optimize such initial compounds via structure diversification with selected combinatorial libraries and computer-aided molecular design. Integrase assays of increasing selectivity will be used, ultimately leading to tests against HIV replication in vivo. Potent inhibitors identified in the initial set will guide the design of second and third generation combinatorial libraries. In the Phase I application, the applicants propose to demonstrate the feasibility of this approach by identifying a collection of new inhibitors active against integrase in vitro. In the Phase II project, the applicants propose to generate second and third generation libraries and use them in an effort to identify inhibitors active in vivo and ultimately applicable clinically.
The U.S. Public Health Service estimated that an excess of 1 million people are infected with HIV in the U.S., where AIDS is the third leading cause of death for all races aged 25-44 years and the sixth cause of death for African-Americans of all ages. The worldwide prevalence of AIDS is greater than 15 million, with the higher occurrence in South America (> 1 million), Asia (> 1.5 million) and Africa ( about 8 million). Viral enzymes play key roles in HIV replication cycle, and as such reverse transcriptase and protease represent an active focus for chemotherapeutic intervention. Currently, the market value of HIV therapeutics is estimated at about $1.5-2 billion for reverse transcriptase inhibitors and $0.8-1 billion for protease inhibitors. Single agent treatments of AIDS are plagued by the development of viral tolerance, which renders therapy ineffective. Combination therapy against multiple viral enzymes, on the other hand, has been shown to provide more effective therapeutic options. However, as HIV rapidly develops drug resistance, new classes of drugs are needed for multiple therapy to effectively control viral replication. HIV integrase is required for HIV replication and is absent in humans. Therefore, this enzyme represents an excellent therapeutic target. The development of integrase inhibitors will enable Biocept to augment the current multiple therapeutic portfolio while theoretically providing minimal toxicity as this enzyme is not found in humans. This will increase the market value of HIV therapeutics.
