This study is looking at how well two new medicines, **GS-3242** and **Lenacapavir (LEN)**, work compared to a combination pill called **Biktarvy**. Biktarvy is made up of three medications: bictegravir, emtricitabine, and tenofovir alafenamide (B/F/TAF). These medicines are for people who have **HIV-1**, a virus that attacks the immune system, and are starting treatment for the first time.

The study has two parts, Phase 2 and Phase 3. In **Phase 2**, they will check how well the new medicines work over a shorter time, either 26 or 35 weeks. In **Phase 3**, they will look at the results after 52 weeks to see how well the new medicines work long-term.

• Study lasts up to 52 weeks.
• Participants must not have used certain HIV medicines before.
• No long-acting HIV treatments should have been used before.

Participants will receive injections of GS-3242 and LEN or take the Biktarvy pill. The study aims to find the best treatment for people newly diagnosed with HIV-1.