Study To Evaluate Emtricitabine/Tenofovir Alafenamide (F/TAF) in Human Immunodeficiency Virus 1 (HIV-1) Infected Children and Adolescents Virologically Suppressed on a 2-Nucleoside/Nucleotide Reverse Transcriptase Inhibitor (2-NRTI)-Containing Regimen

A minimum of 100 participants in total (across all cohorts) aged 1 month to <18 years of age will be enrolled to receive F/TAF. The study will proceed in sequential cohorts as follows: Cohort 1 will switch their current 2-NRTI-containing regimen to F/TAF while continuing on their 3rd ARV agent through 48 weeks; Cohorts 2, 3, and 4 must be on a boosted protease inhibitor (PI) (Cohort 2 only) or any other 3rd ARV agent and will switch their current 2-NRTI-containing regimen to F/TAF while continuing their boosted PI or 3rd ARV agent through 48 weeks. A minimum of 10 participants each in Groups 1 and 2 of Cohort 2, and Cohorts 3 and 4, who are on boosted-ATV as their 3rd ARV agent will be enrolled. Cohorts 2, 3, and 4 will be enrolled by cohort into a two-part study (Parts A and B).

After completion of 48 weeks, all participants will be given the option to participate in an extension phase of the study. Gilead will provide F/TAF until a) The participant turns 18 years old and F/TAF is commercially available for use in adults in the country in which the participant is enrolled or b), F/TAF becomes commercially available for pediatric use in the country in which the participant is enrolled or c), Gilead Sciences elects to terminate development of F/TAF in the applicable country.

However, Cohort 2 (Part B), Cohorts 3 and 4 were not conducted as planned.

Key Inclusion Criteria:

• Human immunodeficiency virus 1 (HIV-1) infected male and female adolescents and children aged 1 month to < 18 years at baseline/Day 1 (according to requirements of the enrolling cohort)
• Must be able to give written assent prior to any screening evaluations
• Parent or guardian able to give written informed consent prior to any screening evaluations and willing to comply with study requirements
• Body weight at screening as follows:

• Cohort 1: ≥ 35 kg
• Cohort 2, Group 1: ≥ 25 kg
• Cohort 2, Group 2: 17 kg to < 25 kg
• Cohort 3: to be updated per a protocol amendment
• Cohort 4: to be updated per a protocol amendment
• Currently on a stable 2-nucleoside/nucleotide reverse transcriptase inhibitor (NRTI) containing regimen that includes a 3rd antiretroviral (ARV) agent for ≥ 6 consecutive months prior to screening
• Plasma HIV-1 ribonucleic acid (RNA) levels < 50 copies/mL for ≥ 6 consecutive months preceding the screening visit
• No opportunistic infection within 30 days of study entry (at baseline/Day 1)
• A negative serum β-human chorionic gonadotropin (HCG) pregnancy test is required for females of childbearing potential only

Key Exclusion Criteria:

• An acquired immunodeficiency syndrome (AIDS) - indicator condition with onset within 30 days prior to screening
• Life expectancy of < 2 years
• Active, serious infections (other than HIV-1 infection) requiring parenteral antibiotic or antifungal therapy within 30 days prior to baseline/Day 1
• Evidence of active pulmonary or extra-pulmonary tuberculosis disease within 3 months of the screening visit
• Active hepatitis C virus (HCV) infection defined as positive for HCV antibody and having detectable HCV RNA
• Positive hepatitis B surface antigen or other evidence of active hepatitis B virus (HBV) infection.
• Have any serious or active medical or psychiatric illness which, in the opinion of the Investigator, would interfere with treatment, assessment, or compliance with the protocol.
• Pregnant or lactating females
• Have history of significant drug sensitivity or drug allergy
• Have previously participated in an investigational trial involving administration of any investigational agent, other than TDF, within 30 days prior to the study dosing

NOTE: Other protocol defined Inclusion/ Exclusion criteria may apply.