Novel HIV capsid-targeting antivirals maintain activity against lenacapavir-resistant viruses - PROJECT SUMMARY Despite advances in highly active retroviral therapy (HAART), HIV continues to be a global health concern. The most commonly used anti-HIV drugs in the clinic have included combinations of antivirals which target the essential viral enzymes reverse transcriptase, integrase, and protease. Over the course of treatment, HIV develops resistance to many of these compounds, decreasing the efficacy of these therapies. Hence, new targets have been sought to combat resistance. Lenacapavir (LEN) is the first antiviral targeting the HIV capsid protein (CA) to be approved by the FDA in 2023. Despite its high potency and long-acting formulation, several mutations have been identified in vitro and in patients taking LEN-based therapies. In fact, many mutations, including M66I, Q67H, and N74D have been reported to appear in patients within days or weeks of LEN-based therapy. Hence, it appears that LEN has a low genetic barrier to resistance. Therefore, next-generation compounds that can bind the HIV CA in the presence of these mutations would be very valuable and may provide the possibility to rescue LEN-based treatments after failure. We have studied for several years HIV CA-targeting antivirals that bind the same pocket as LEN and another CA-targeting antiviral PF74. Recently, we identified a compound, that while not as potent as LEN, appears to bind 2-fold better to M66I CA hexamer compared to WT and has only 2-fold resistance to M66I virus compared to WT in antiviral cell-based assay (by comparison, M66I reportedly causes >50,000-fold resistance to LEN in vitro). In additional preliminary data, we solved the crystal structure of this compound in complex with WT and M66I CA (at 2.0 and 2.1 Å, respectively), which gives atomic level details about interactions with I66. These exciting preliminary results set the stage for novel antiviral design strategies to generate compounds that can target multiple LEN-resistant mutations. We hypothesize that different chemical substitutions in distinct regions of the lead compounds differentially affect potency against WT and various mutant CAs. The following specific aims will address our hypothesis: Aim 1. Synthesis of analogs designed to target clinically-relevant LEN-resistant mutations. Aim 2. Biophysical and virological characterization of analogs. Aim 3. Structural characterization of analogs. Overall, these studies should provide valuable insights into how different chemical substitutions can affect the potency of CA-targeting antivirals against WT and LEN-resistant HIV. These studies will provide the framework for future studies toward the design of potent antivirals targeting CA to improve therapeutic treatment options for people living with HIV.
