Switch to Doravirine/Islatravir (DOR/ISL) in Human Immunodeficiency Virus 1 (HIV-1) Participants Treated With Bictegravir/Emtricitabine/Tenofovir Alafenamide (BIC/FTC/TAF) (MK-8591A-018)

Prior treatment

• Is taking or is anticipated to require systemic immunosuppressive therapy, immune modulators, or any prohibited therapies.
• Is currently participating in or has participated in a clinical study with an investigational compound or device from 45 days prior to Day 1 through the study treatment period.

Other illness

• Has HIV-2 infection.
• Has an active diagnosis of hepatitis due to any cause, including active Hepatitis B Virus (HBV) co-infection.

Age

• Has a history of malignancy ≤5 years prior to signing informed consent except for adequately treated basal cell or squamous cell skin cancer, in situ cervical cancer, or cutaneous Kaposi's sarcoma.

Other

• Has a documented or known virologic resistance to doravirine (DOR).
• expects to conceive or donate eggs at any time during the study.

• Is HIV-1 positive with plasma Human Immunodeficiency Virus 1 (HIV-1) RNA \<50 copies/mL at screening.
• Has been receiving bictegravir/emtricitabine/tenofovir alafenamide (BIC/FTC/TAF) therapy with documented viral suppression (HIV-1 RNA \<50 copies/mL) for ≥3 months prior to signing informed consent and has no history of prior virologic treatment failure on any past or current regimen.
• Females are eligible to participate if not pregnant or breastfeeding, and at least one of the following conditions applies: Is not a woman of childbearing potential (WOCBP); is a WOCBP and using an acceptable contraceptive method, or be abstinent from heterosexual intercourse as their preferred and usual lifestyle; a WOCBP must have a negative highly sensitive pregnancy test (\[urine or serum\] as required by local regulations) within 24 hours before the first dose of study intervention; if a urine test cannot be confirmed as negative (e.g. an ambiguous result), a serum pregnancy test is required. In such cases, the participant must be excluded from participation if the serum pregnancy result is positive.