The purpose of this study is to evaluate the safety, tolerability, 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) compared to placebo, to induce HIV-1 control during analytic treatment interruption (ATI).

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.

Inclusion Criteria

• Provision of written informed consent.
• History of Initiation of combination ART within 90 days of acute HIV diagnosis
• On ART for at least 12 months with no known ART interruption >28 consecutive days within 12 months prior to Step 1 Study Entry
• ART with an integrase inhibitor-based regimen with two NRTIs or dolutegravir/lamivudine regimen for at least 6 weeks prior to Study Entry.
• Willingness to participate in the ATI and willingness to restart ART according to study guidelines.
• Willingness to adhere to protocol therapy and complete all study visits.
• Weight ≥50 kg and ≤150 kg at Screening.
• CD4 cell count ≥450 cells/mm3 obtained within 60 days prior to Study Entry.
• HIV-1 RNA <50 copies/mL (or below the assay limit of quantification if local assay lower limit of quantification is >50 copies/mL) for at least 1 year and within 60 days prior to Study Entry.
• Select laboratory results within 60 days of study entry
• For cisgender women and transgender men of reproductive potential, negative urine or serum pregnancy test within 48 hours prior to or at study Entry.
• Participants who are able to become pregnant and who are engaging in sexual activity that could lead to pregnancy must agree to use two methods of contraception, one of which must be a highly effective methods for contraception. Barrier methods of contraception are required for the second method of contraception.
• Availability of results of HLA typing (required for randomization).
• Completion of pre-entry leukapheresis or LVBD.

Exclusion Criteria

• Currently pregnant or breastfeeding or planning to become pregnant during study participation.
• Prior receipt of anti-HIV broadly neutralizing antibody therapy.
• Receipt of any non-HIV monoclonal antibody therapy within 1 year prior to study entry.
• Prior receipt of a latency-reversing agent (LRA).
• Receipt of HIV-1 or other investigational vaccines within 6 months prior to Study Entry.
• Receipt of a live-virus vaccine within 60 days or any vaccination within 14 days prior to Study Entry.
• Receipt of any simian adenovirus-vectored vaccine (e.g., anti-COVID-19 AZD1222) within 12 months prior to Step 1 Study Entry.
• Known allergy/sensitivity or any hypersensitivity to components of study treatments or their formulations.
• Known severe chicken egg allergy.
• Known history of a severe reaction or anaphylaxis to prior vaccinations or antibody preparations (e.g., intravenous immunoglobulin).
• Significant drug sensitivity or drug allergy (such as anaphylaxis or hepatoxicity).
• Any history of anaphylaxis and related symptoms such as hives, respiratory difficulty, or angioedema.
• Previous or current history of bleeding factor deficiency, coagulopathy or platelet disorder or on chronic anticoagulation.
• History of inflammatory neurologic diseases.
• History of pregnancy, head trauma or major surgery within 90 days prior to Step 1 Study Entry.
• History of use of any immunomodulatory medications within the 6 months prior to Step 1 Study Entry.
• Significant serious skin disease, such as but not limited to active rash, eczema, psoriasis, or urticaria.
• Autoimmune disease (e.g., lupus, multiple sclerosis, and others) requiring ongoing immunosuppression.
• Known history of CDC Stage 3 opportunistic infection (OI).
• Any history of an HIV-associated malignancy.
• Known or suspected active or untreated latent Mycobacterium tuberculosis infection.
• Active or recent non-HIV-associated malignancy.
• Serious illness requiring systemic treatment and/or hospitalization within 90 days prior to study entry.
• Known resistance to one or more drugs in two or more ARV drug classes.
• History of or current clinical atherosclerotic cardiovascular disease
• Current advanced liver disease.
• Use of complementary or alternative medicines within 14 days prior study entry.

Beginning 3 months following publication and available throughout period of funding of the AIDS Clinical Trials Group by NIH.

• With whom? Researchers who provide a methodologically sound proposal for use of the data that is approved by the AIDS Clinical Trials Group.
• For what types of analyses? To achieve aims in the proposal approved by the AIDS Clinical Trials Group.
• By what mechanism will data be made available? Researchers may submit a request for access to data using the AIDS Clinical Trials Group "Data Request" form at: https://actgnetwork.org/submit-a-proposal/. Researchers of approved proposals will need to sign an AIDS Clinical Trials Group Data Use Agreement before receiving the data.