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)

Inclusion Criteria:

• Is HIV-1 positive with plasma Human Immunodeficiency Virus 1 (HIV-1) RNA <50copies/mL at screening.

• Has been receiving 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 ofprior virologic treatment failure on any past or current regimen.

• Female is eligible to participate if she is not pregnant or breastfeeding, and atleast one of the following conditions applies: Is not a woman of childbearingpotential (WOCBP); is a WOCBP and using an acceptable contraceptive method, or beabstinent from heterosexual intercourse as their preferred and usual lifestyle; aWOCBP must have a negative highly sensitive pregnancy test ([urine or serum] asrequired by local regulations) within 24 hours before the first dose of studyintervention; if a urine test cannot be confirmed as negative (e.g. an ambiguousresult), a serum pregnancy test is required. In such cases, the participant must beexcluded from participation if the serum pregnancy result is positive.

Exclusion Criteria:

• Has HIV-2 infection.

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

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

• Is taking or is anticipated to require systemic immunosuppressive therapy, immunemodulators, or any prohibited therapies.

• Is currently participating in or has participated in a clinical study with aninvestigational compound or device from 45 days prior to Day 1 through the studytreatment period.

• Has a documented or known virologic resistance to DOR.

• Female expects to conceive or donate eggs at any time during the study.