This study will evaluate how safe Budigalimab is and how it moves within the body in adult participants with HIV-1 infection.

Budigalimab is an investigational drug being evaluated for the treatment of Human Immunodeficiency Virus. Study participants will be assigned to one of the 4 treatment groups and will receive a single dose of Budigalimab or placebo subcutaneous (SC) and intravenous (IV). Around 32 participants 18-65 years of age living with Human Immunodeficiency Virus will be enrolled in the study in approximately 9 sites worldwide.

Each participant will receive single dose of SC and IV Budigalimab and/or Placebo on day 1 and will be followed for 24 weeks.

Participants will attend weekly to every two and every four weeks visits during the study at a hospital. The effect of the treatment will be checked by medical assessments, blood tests and checking for side effects. There may be higher treatment burden for participants in this trial.

Inclusion Criteria:

• Condition of generally good health, body mass index ≥ 18.0 to < 35.0 kg/m2.
• Laboratory values must meet acceptable criteria.
• Human Immunodeficiency Virus (HIV-1) infected on antiretroviral therapy (ART) for at least 12 months prior to screening and on current ART regimen for at least 8 weeks prior to screening.
• CD4 cell count ≥ 450 cells/μL at Screening and during the 12 months prior to Screening.
• Plasma HIV-1 RNA below the lower limit of quantification at Screening and at least 6 months prior to Screening.
• Participants agreeing to use an effective barrier method of protection (male and/or female condom) during sexual activity from Study Day 1 through last study visit for the purposes of prevention of HIV transmission.

Exclusion Criteria:

• Participants with signs/symptoms associated with SARS-CoV-2 infection OR Current SARS-CoV-2 infection by any viral nucleic acid test completed within 7 days prior to the Day 1 dose.
• Participants having history or ongoing diagnosis of acquired immunodeficiency syndrome (AIDS)-defining illness.
• Participants having history of or active immunodeficiency (other than HIV).
• Participants having active autoimmune disease or history of autoimmune disease that has required systemic treatment.
• Prior therapy/exposure to budigalimab or any other immune checkpoint inhibitor [e.g., anti-programmed cell death protein 1(PD-1), anti-PD-L1, anti-PD-L2, anti-CTLA4].
• Participants having clinically significant medical disorders that might expose the subjects to undue risk of harm, confound study outcomes, or prevent the subject from completing the study.
• Participants having active or suspected malignancy or history of malignancy (other than basal cell skin cancer or cervical carcinoma in situ) in the past 5 years.
• Participants with history of or active tuberculosis (TB) at screening.
• Participants having known psychiatric or substance abuse disorders that would interfere with adherence to study requirements.
• Participants who have received immunomodulatory or immunosuppressive (including IV/orally administered [PO] steroids at any dose, but excluding steroids that are inhaled, topical or via local injection) therapy within 24 weeks prior to the first dose of study drug.