Doravirine (DOR) in Human Immunodeficiency Virus (HIV)-Infected Children Ages 4 Weeks to <12 Years and <45 kg (MK-1439-066)

Inclusion Criteria:

• Has HIV-1 infection confirmed at screening

• Has treatment history defined as either TN or with documented viral suppression (HIV-1 RNA <50 copies/mL) for ≥3 months on combination antiretroviral therapy (cART)

• Body weight is >3 kg to <45 kg

• If female, is not pregnant or breastfeeding, and one of the following applies:

• is not a woman of childbearing potential (WOCBP)

• is a WOCBP using an acceptable form of contraception, or is abstinent

• if a WOCBP must have a negative pregnancy test (urine or serum) within 24 hours ofthe first dose of study intervention

Study Extension Inclusion Criteria:

• Has completed the Week 96 visit.

• Is considered, in the opinion of the investigator, to have derived benefit fromtreatment with DOR plus the 2 NRTIs selected by the investigator, or DOR/3TC/TDF, byWeek 96 of the study

• Is considered, in the opinion of the investigator, to be a clinically appropriatecandidate for additional treatment with DOR plus 2 NRTIs selected by theinvestigator.

• Understands the procedures in the study extension and has provided (or have theparticipant's legally acceptable representative, if applicable, provide) documentedinformed consent/assent to enter the study extension and continue treatment with DORplus 2 NRTIs selected by the investigator until DOR is available commercially incountries participating in the study or for up to an additional 224 weeks (whichevercomes first).

Exclusion Criteria:

• Has evidence of renal disease

• Demonstrates evidence of liver disease

• Has clinical or laboratory evidence of pancreatitis

• Has any history of malignancy

• Has presence of any active acquired immunodeficiency syndrome (AIDS)-definingOpportunistic Infection

• Has an active diagnosis of hepatitis, including hepatitis B co-infection

• Has current active tuberculosis and/or is being treated with a rifampicin-containingregimen

• Has a medical condition that precludes absorption or intake of oral pellets/granules

• Has a history or current evidence of any condition, therapy, laboratory abnormality,or other circumstance that might confound results of the study or interfere withparticipating for the entire duration of the study

• Is taking or is anticipated to require systemic immunosuppressive therapy, immunemodulators, or other prohibited therapy

• Is currently participating in or has participated in an interventional clinicalstudy with an investigational compound or device from 45 days prior to Day 1 throughthe treatment period

• Has a documented or known virologic resistance to DOR

• Has any history of viremia (HIV RNA >1000 copies/mL) after at least 3 months on anon-nucleoside reverse transcriptase inhibitor (NNRTI)-based regimen