Study to Evaluate the Efficacy, Safety, and Tolerability of Long-acting Intramuscular Cabotegravir and Rilpivirine for Maintenance of Virologic Suppression Following Switch From an Integrase Inhibitor in HIV-1 Infected Therapy Naive Participants

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) \

Inclusion Criteria: - HIV-1 infected, ART-naive men or women aged 18 years or greater at the time of signing the informed consent. - HIV-1 infection as documented by Screening plasma HIV-1 RNA \>=1000 c/mL; - Antiretroviral-naive (\ 3.25 is exclusionary; Fib-4 scores 1.45 - 3.25 requires Medical Monitor consultation. Fibrosis 4 Score Formula: (Age x AST)/(Platelets x \[square root of ALT\]). - Unstable liver disease (as defined by any of the following: presence of ascites, encephalopathy, coagulopathy, hypoalbuminemia, esophageal or gastric varices, or persistent jaundice), known biliary abnormalities (with the exception of Gilbert's syndrome or asymptomatic gallstones or otherwise stable chronic liver disease per investigator assessment). - History of liver cirrhosis with or without hepatitis viral co-infection. - Ongoing or clinically relevant pancreatitis. - All participants will be screened for syphilis (rapid plasma reagin \[RPR\]). Participants with untreated syphilis infection, defined as a positive RPR without clear documentation of treatment, are excluded. Participants with a positive RPR test who have not been treated may be rescreened at least 30 days after completion of antibiotic treatment for syphilis. - Ongoing malignancy other than cutaneous Kaposi's sarcoma, basal cell carcinoma, or resected, non-invasive cutaneous squamous cell carcinoma, or cervical, anal or penile intraepithelial neoplasia; other localized malignancies require agreement between the investigator and the study Medical Monitor for inclusion of the participant prior to enrollment. - Any condition which, in the opinion of the Investigator, may interfere with the absorption, distribution, metabolism or excretion of the drug or render the participant unable to receive study medication. - History or presence of allergy or intolerance to the study drugs or their components or drugs of their class. In addition, if heparin is used during pharmacokinetic sampling (PK) sampling, participants with a history of sensitivity to heparin or heparin-induced thrombocytopenia must not be enrolled. - Current or anticipated need for chronic anti-coagulation. - Alanine aminotransferase (ALT) \>=3 times upper limit normal (ULN). - Clinically significant cardiovascular disease, as defined by history/evidence of congestive heart failure, symptomatic arrhythmia, angina/ischemia, coronary artery bypass grafting (CABG) surgery or percutaneous transluminal coronary angioplasty (PTCA) or any clinically significant cardiac disease. - Exposure to an experimental drug and/or experimental vaccine within 28 days or 5 half-lives of the test agent, or twice the duration of the biological effect of the test agent, whichever is longer, prior to the first dose of investigational product (IP). - Treatment with any of the following agents within 28 days of Screening: radiation therapy; cytotoxic chemotherapeutic agents; tuberculosis (TB) therapy, with the exception of treatment of latent TB with isoniazid; Immunomodulators that alter immune responses (such as chronic systemic corticosteroids, interleukins, or interferons). Note: Participants using short-term (e.g. =\