Mechanism of action of an HIV-1 maturation inhibitor

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DESCRIPTION (provided by applicant): There is an urgent need for new drugs to treat HIV/AIDS, particularly the discovery and development of compounds that are active against virus isolates resistant to currently approved therapies. During my pre-academic career, we reported on 3-O-(3',3'-dimethylsuccinyl) betulinic acid (PA-457), first in a new class of HIV-1 maturation inhibitors with efficacy against strains resistant to current therapies. Unlike protease inhibitors, PA-457 blocks a single step in the processing of the viral Gag protein: protease cleavage of the Gag capsid (CA) precursor (CA-SP1) to mature CA protein. This results in the release of immature, non-infectious viral particles, and also raises several interesting questions about the mechanism of action, molecular determinants, and identity of molecular target for this novel HIV-1 inhibitor. I would like these questions along with the development of additional maturation inhibitors to be the center of my career research. I would like to establish myself as a productive scientist in retrovirus maturation, a relatively unexplored research area. Work by our group and others has demonstrated that residues within the HIV-1 Gag CA-SP1 boundary region serve as determinants of PA-457 activity, and genetic variation within this region allows HIV-1 to escape PA-457-mediated inhibition. More recent results support the theory that a direct interaction between the compound and an oligomeric form of Gag is critical to PA-457 activity. While these observations allow insight into the PA-457 antiviral effect, the mechanisms of action and resistance of PA-457 remain to be fully determined. We propose to further characterize the mechanism of action of PA-457 activity and further elucidate the molecular determinants of PA-457 activity. We believe that the results of our studies will provide greater insight into the mechanisms of action and resistance of PA-457 as well as into the precise molecular determinant of PA-457 activity. A better understanding of these issues is particularly relevant due to PA-457's ongoing clinical development (currently in Phase 2b trial). We are confident that the results of these studies will aid in the development of additional classes of HIV-1 maturation inhibitors and help elucidate the basic mechanism of HIV-1 maturation. Lay Language: Drug resistance is the leading reason for HIV treatment failure. Completion of the proposed research will help identify novel HIV maturation inhibitors, provide additional treatment options, and improve disease outcome.