The goal of this study is to learn how well long-acting lenacapavir works to prevent human immunodeficiency virus (HIV) infection in people at higher risk of getting HIV in Brazil. The study will also learn about safety, continued use over time, and whether people prefer this option compared to daily oral pre- exposure prophylaxis (PrEP). The main questions it aims to answer are:

How many participants get HIV while using long-acting lenacapavir? How safe is long-acting lenacapavir in real-world health services? How many participants continue using their chosen prevention method over time? What factors help or make it harder for participants to stay on prevention? Researchers will compare two HIV prevention options to understand how they work in routine care: Long-acting lenacapavir, given as an injection under the skin every 6 months, Daily oral pre-exposure prophylaxis (PrEP), taken as a pill containing tenofovir disoproxil fumarate and emtricitabine, Participants will choose the prevention option they prefer after receiving counseling. This is not a randomized study. Researchers will follow participants for up to 2 years. Participants will: Receive either an injection every 6 months or take a daily pill, Visit the clinic regularly for HIV testing and health checkups, Receive testing and treatment for sexually transmitted infections, Answer questions about their health, medication use, and experiences, Receive prevention counseling and condoms. This study will help health services understand how to offer long-acting HIV prevention in Brazil and how to better support people who want to prevent HIV infection.

Inclusion Criteria:

Ability to understand and sign the Informed Consent Form, which must be obtained before the initiation of any study procedures, and willingness to comply with the protocol requirements

Be a cisgender man, a non-binary person designated male at birth, or a transgender woman or transgender man

Report having engaged in anal sex with a person designated male at birth within the last six months

Be between 16 and 30 years of age

Have a body weight equal to or greater than 35 kilograms

Seek care at a participating study clinic for human immunodeficiency virus testing or initiation of human immunodeficiency virus pre-exposure prophylaxis, either spontaneously or through peer invitation

Have a non-reactive result on a rapid test for human immunodeficiency virus

Be an individual without prior use of human immunodeficiency virus pre-exposure prophylaxis, or an individual with prior use who remains in a situation of vulnerability, characterized by:

a history of oral human immunodeficiency virus pre-exposure prophylaxis with at least two prior dispensations without return for a new pickup in the six months preceding the enrollment visit, or

a history of long-acting cabotegravir use with a delay of at least one scheduled reload dose

Exclusion Criteria:

Known hypersensitivity to the study medication, its metabolites, or formulation excipients

Severe hepatic impairment or a history or current clinical condition of decompensated liver cirrhosis, such as ascites, encephalopathy, or variceal bleeding

Known or suspected severe active infection, such as active tuberculosis

Need for continuous use of contraindicated concomitant medications

Any clinical or psychosocial condition, or prior treatment, that in the opinion of the investigator makes the participant unsuitable for the study or unable to comply with dosing requirements

Confirmed or suspected infection with the human immunodeficiency virus

Plans to move outside the study area during the follow-up period

Prior participation in a clinical study using Lenacapavir in the PURPOSE study

Prior participation in a human immunodeficiency virus vaccine study, except in cases where the participant provides documentation demonstrating receipt of placebo and not the active product

Current participation in another interventional human immunodeficiency virus prevention study that, in the opinion of the investigator, may interfere with the conduct of this study