Open-label, Follow-up of Doravirine/Islatravir (DOR/ISL 100 mg/0.75mg) for Participants With Human Immunodeficiency Virus-1 (HIV-1) Infection (MK-8591A-033)

Inclusion Criteria: * Is currently receiving DOR 100 mg/ISL 0.75 mg adult FDC tablet in an MSD-sponsored clinical study and has completed the last treatment visit. * Is considered by the investigator to have derived clinical benefit from receiving DOR/ISL and for whom further treatment with DOR/ISL is considered clinically appropriate. * Female is not pregnant or breastfeeding, and at least one of the following conditions applies: Is not a woman of childbearing potential (WOCBP); or is a non-pregnant WOCBP who agrees to the following during the intervention period and for at least 6 weeks after the last dose of study intervention: Not be sexually active, or if sexually active, to use an acceptable method of contraception; or is pregnant and continues to receive study intervention (where allowed by local regulations and as appropriate based on available data/local standard-of-care guidelines) Exclusion Criteria: * Is taking or is anticipated to require any prohibited therapies.