Evaluation of Safety, Immunogenicity and Efficacy of a Triple Immune Regimen in Adults Initiated on ART During Acute HIV-1

A5374 is a phase I/IIa randomized, two-arm, double-blind placebo-controlled, multi-step strategy trial to evaluate safety and efficacy of therapeutic vaccination with chimpanzee adenovirus ChAdOx1- and poxvirus modified vaccinia Ankara (MVA)-vectored conserved mosaic T-cell vaccines in a sequential regimen with the toll-like receptor 7 (TLR7) agonist vesatolimod (VES) and two broadly neutralizing antibodies (bNAbs) of the CD4 binding site and V3-loop base classes in individuals with HIV-1 who started suppressive antiretroviral therapy (ART) during acute HIV-1. Participants will be screened for eligibility and have a pre-entry visit. After determination of eligibility, participants will be randomized prior to entry to either the active intervention arm (Arm A) or the placebo arm (Arm B) in a 2:1 ratio. The study consists of four steps including an analytic treatment interruption (ATI) for all participants, and two subsequent optional steps including a second ATI for placebo participants. * Step 1: Study Intervention and ART (67 weeks) * Step 2: Analytic Treatment Interruption (up to 24 weeks) * Step 3: ART Restart (24 weeks) * Step 4: Continuation of ATI (up to 24 weeks) * Step 5 (optional): Study Intervention and ART (Placebo roll-over) * Step 6 (optional): Analytic Treatment Interruption 2 (ATI 2) Each participant will complete Step 1 and Step 2. At any time on Step 2\[mw1.1\]\[KM1.2\], participants on Arm A who meet criteria to restart ART will enter Step 3 and resume ART. Arm B (placebo) participants who have experienced virologic restart criteria may choose to enter Step 3 to resume ART or elect to enter Step 5 to resume ART and receive active study products. Participants who elect to enter Step 5 will undergo second ATI in Step 6. Participants who do not meet ART restart criteria after 24 weeks in Step 2 will enter Step 4 for an extended ATI. Each participant will be enrolled for up to approximately 110 weeks. The total time on study for each participant is dependent on the time spent in the treatment interruption steps (Step 2 and 4). Eligible participants participating in for Steps 5 and 6 will have up to 110 additional weeks on study.