Temsavir (BMS-626529) is an attachment inhibitor (AI) in clinical development (administered as prodrug BMS-663068) that binds to HIV-1 gp120. Temsavir displays in vitro activity against HIV-1 envelopes with C-C chemokine receptor type 5 (CCR5-), C-X-C chemokine receptor type 4 (CXCR4), and dual tropism. It also is active against almost all HIV-1 subtypes tested except for subtype CRF01-AE and possibly group O. Temsavir can inhibit both CD4-induced and CD4-independent formation of the "open state" four-stranded gp120 bridging sheet, and the subsequent formation and exposure of the chemokine co-receptor binding site. This unique mechanism of action prevents the initial interaction of HIV-1 with the host CD4+ T cell, and subsequent HIV-1 binding and entry. Temsavir is administered as a phosphonooxymethyl ester prodrug (BMS-663068), which was developed to improve the solubility and dissolution of Temsavir. Temsavir is currently being investigated clinically through the use of the prodrug BMS-663068, and a Phase III study of BMS-663068 in HIV-1-infected treatment-experienced subjects is ongoing (NCT02362503).