Development of HIV capsid-targeting antivirals that affect immune response by modulating capsid stability and have improved resistance profiles

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PROJECT SUMMARY The HIV-1 capsid (CA) is a protein that plays a major role in multiple steps of the virus life cycle. During the previous funding cycle we solved the elusive structure of the intact native full length hexameric HIV-1 CA revealing previously unknown molecular details, especially at the 3-fold and 2-fold intra-hexamer interfaces that affect core stability. We also solved >45 CA structures that include mutations that modulate core stability, thus providing the first glimpses of the molecular basis of core stabilization that is critical in designing potential therapeutics. Additional structures were in complex with host factor peptides, or a variety of novel inhibitors. In addition, we synthesized and characterized >220 compounds that target the PF74-binding pocket. Among them are compounds with much higher potency than PF74, and importantly, compounds with improved resistance profile compared to GS-6207, a highly potent CA-targeting drug in clinical trials. In addition to strong CA hexamer stabilizers, we introduced an innovative class of compounds, “destabilizers” of CA hexamers, raising the exciting prospect of core destabilization that may lead to premature capsid uncoating and interferon upregulation. We will use a combination of chemical synthesis, virological, biophysical, and crystallography approaches to synthesize a number of compounds that improve potency through new inter- and intra-protomer interactions; overcome GS-6207 resistance mutations; modulate core stability and upregulate interferon response; enable interactions with CA through innovative mechanisms, including covalent crosslinking. The compounds will be characterized and the structure activity relationship studies will be guided by X-ray crystallography, biophysical studies (time-lapse imaging, thermal shift, assembly kinetics assays) and virological characterization of mechanism of action as well as drug resistance studies. The research will be conducted by the groups of Stefan Sarafianos at Emory Univ (structure, biophysics, virology) and ZQ Wang (chemical synthesis, Univ of Minnesota), Eric Freed at DRP-NCI (virology), and in collaboration with Greg Melikian (imaging). The proposed studies will advance our understanding of the structural basis of core stability, which controls a large number of steps in the virus life cycle. They will also lead to the identification of innovative compound leads with novel “CA-destabilizing” mechanisms of action, high potency, improved resistance profiles, CA-crosslinking functionalities, and improved pharmacological properties.