The goal of this study is to evaluate the efficacy of the study drugs, lenacapavir (LEN) in preventing HIV infection, in participants ≥ 16 years of age who have condomless receptive anal sex with partners assigned male at birth and are at risk for HIV-1 infection. The primary objective of this study is to evaluate the efficacy of LEN for HIV-1 PrEP in participants ≥ 16 years of age who have condomless receptive anal sex with partners assigned male at birth at risk of HIV-1 infection.