The First Long-Acting Injectable Regimen (FLAIR) study is being conducted to establish if human immunodeficiency virus type-1 (HIV-1) infected adult participants whose virus is virologically suppressed on an integrase inhibitor single tablet regimen (INI STR) will remain suppressed after switching to a two-drug intramuscular (IM) long-acting (LA) regimen of cabotegravir ▼ (CAB) and rilpivirine ▼ (RPV). In this study, the INI STR will be limited to abacavir/dolutegravir/lamivudine (ABC/DTG/3TC). FLAIR is a Phase 3, multi-phase, randomized, open label, active controlled, multicenter, parallel-group, non-inferiority study in HIV-1, anti-retroviral therapy (ART)-naïve adult participants. This study is designed to demonstrate the non-inferior antiviral activity of switching to a two drug CAB LA 400 mg + RPV LA 600 mg regimen every 4 weeks (Q4W: monthly) compared to remaining on ABC/DTG/3TC over 48 weeks (4 weeks oral CAB + RPV, 44 weeks LA therapy). Participants who are HLA-B*5701 positive at Screening may enroll into the study and receive DTG plus a NON-ABACAVIR containing dual nucleoside reverse transcriptase inhibitor (NRTI) regimen. Eligible participants will enroll into the Induction Phase of the study and receive ABC/DTG/3TC for 20 weeks (Week [-20] to Day 1). Participants who have an HIV 1 ribose nucleic acid (RNA) <50 copies per milliliter (c/mL) at Week (-4) will be randomized (1:1) into the Maintenance Phase at Day 1 to either continue ABC/DTG/3TC or to discontinue ABC/DTG/3TC and begin oral therapy with CAB 30 mg + RPV 25 mg once daily for approximately 4 Weeks, followed by monthly CAB LA + RPV LA injections from visit Week 4b until study completion or withdrawal. Participants who successfully complete Week 100 (without meeting study defined withdrawal criteria and who remain virologically suppressed through Week 96: HIV-1 RNA <50 c/mL) will be given the option to switch to the LA arm in the Extension Phase (using an optional oral lead-in with CAB + RPV) or be withdrawn from the study. Participants will continue to receive injections every 4 weeks during the Extension Phase until CAB LA and RPV LA are either locally approved and commercially available, the participant no longer derives clinical benefit, the participant meets a protocol-defined reason for discontinuation, or until development of either CAB LA or RPV LA is terminated.