This study is for adults with HIV who are currently being treated with Biktarvy® (bictegravir/emtricitabine/tenofovir alafenamide [B/F/TAF]). The purpose of the research is to compare the effectiveness of B/F/TAF and the investigational once-daily medication Bictegravir/Lenacapavir (BIC/LEN). Participants will either continue taking B/F/TAF or switch to BIC/LEN for at least 48 weeks. The study will also look at the long-term effectiveness of BIC/LEN. Participants will be given the option of participating in an open-label phase of the study (where both the provider and participant know which drug they are on) where all participants receive BIC/LEN.

The primary objective of this study is to determine how bictegravir (BIC) plus lenacapvir (LEN) in two different doses affects an HIV-1 infection in the body compared with current standard treatment regimens. Other objectives are to determine which of these treatments are the most effective for treating HIV-1 infection, the safety and tolerability of these two doses for people with HIV, as well as how long it stays in the body using physical exams, laboratory tests, ECG, blood analysis, and any symptoms or problems experienced during the study.