This study is testing the safety and how the body processes two drugs, TAF and EVG, given as rectal inserts. These drugs are being checked for use in preventing HIV, a virus that attacks the immune system. In this study, some people will get the real drugs, and others will get a placebo, which is a fake treatment. The study lasts several weeks and includes two phases. Participants will place the inserts themselves and visit the clinic for tests and sample collections.

• **Duration**: Participants will be involved in study visits over a period of weeks.
• **Visits**: Participants need to attend multiple clinic visits for sample collection and monitoring.
• **Compensation**: Participants might be compensated for their time and involvement.

To join, you must be 18-59 years old, HIV-negative, and willing to give blood and other samples. You should not have liver or kidney problems, bowel diseases, or be taking certain medications. Also, you must agree to use birth control if needed. If you are pregnant or breastfeeding, you cannot join. This study is looking for people who are comfortable with the testing process and committed to following study rules.