This study is being conducted to investigate a new treatment approach for people living with HIV. The research focuses on testing the effectiveness and safety of two experimental drugs, islatravir and ulonivirine, which are combined in a single medication known as MK-8591B. This combination is intended to be taken once a week. The study will compare this weekly regimen against a standard daily medication containing bictegravir, emtricitabine, and tenofovir alafenamide.

The goal of the study is to evaluate how well the experimental treatment controls the HIV-1 RNA, which is a measure of the amount of virus in the blood. The research also aims to monitor the safety and how well the body tolerates the medications over time. During the course of the study, participants will be observed for a set period to track changes in their viral levels and their CD4+ T-cell count, which is a type of white blood cell that helps the body fight infections.

The study is divided into two stages. In the first stage, the effectiveness and safety of the weekly treatment are assessed in an open manner. In the second stage, a more controlled method is used where neither the participants nor the researchers know which specific treatment is being administered to ensure unbiased results. Participants will be monitored through various stages of the study to collect data on how the virus responds to the treatment and to identify any potential side effects.