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 particpants 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. At the end of the Maintenance phase, eligible participants who were randomized to continue ABC/DTG/3TC will be given an option to switch to LA therapy at Week 100. Those participants (HIV 1 RNA <50 c/mL at Week 96) will transition to LA dosing, beginning with approximately 4 weeks oral CAB + RPV therapy at Week 100, and receive the first IM CAB LA + RPV LA injections at Week 104b. 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.