Fostemsavir/temsavir is an investigational HIV-1 entry inhibitor currently in late-stage clinical trials. Although it holds promise to be a first-in-class Env-targeted entry inhibitor for the clinic, issues with bioavailability relegate its use to salvage therapies only. As such, the development of a small molecule HIV-1 entry inhibitor that can be used in standard combination antiretroviral therapy (cART) remains a longstanding goal for the field. We previously demonstrated the ability of extending the chemotypes available to this class of inhibitor as the first step towards this overarching goal. In addition to poor solubility, metabolic stability is a crucial determinant of bioavailability. Therefore, in this short communication, we assess the metabolic stabilities of five of our novel chemotype entry inhibitors. We found that changing the piperazine core region of temsavir alters the stability of the compound in human liver microsome assays. Moreover, we identified an entry inhibitor with more than twice the metabolic stability of temsavir and demonstrated that the orientation of the core replacement is critical for this increase. This work further demonstrates the feasibility of our long-term goal—to design an entry inhibitor with improved drug-like qualities—and warrants expanded studies to achieve this.
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