Inclusion Criteria:

• Clinical diagnosis of systemic lupus erythematosus (SLE) at least 24 weeks prior to screening as defined by the 2019 European Alliance of Associations for Rheumatology (EULAR)/ American College of Rheumatology (ACR) classification criteria for SLE.

• At Screening, must have at least one of the following:

  • antinuclear antibody (ANA) positive (titer >= 1:80)
  • anti-double stranded deoxyribonucleic acid (dsDNA) positive
  • anti-Smith positive

• Hybrid systemic lupus erythematosus disease activity index (hSLEDAI) >= 6, of which >= 4 points are clinical (not based on laboratory criteria), independently reviewed by the MCDR at Screening. Clinical hSLEDAI score (not based on laboratory criteria) must be re-confirmed as >= 4 at the Baseline visit. Lupus headache or organic brain syndrome do not count towards the hSLEDAI points required for eligibility but should be documented on the hSLEDAI if present.

• Physician's Global Assessment (PhGA) >= 1 during screening period.

• On stable background treatment for >= 60 days prior to Baseline (with the exception of oral corticosteroid [OCS], which must be at a stable dose for >=14 days prior to Baseline) with

  • antimalarial(s) [hydroxychloroquine <= 400 mg daily, chloroquine <= 500 mg daily, quinacrine <= 100 mg daily];
  • and/or prednisone (or prednisone-equivalent) (<= 20 mg daily);
  • and/or no more than 1 of the following: azathioprine (<= 150 mg daily), 6-mercaptopurine (<= 150 mg daily), mycophenolate mofetil (<= 2 g daily), mycophenolate sodium <= 1,440 mg/day, leflunomide (<= 20 mg daily), cyclosporine, tacrolimus, voclosporin (<= 23.7 mg twice daily), methotrexate (<= 25 mg weekly), or mizoribine (<= 150 mg daily).

Exclusion Criteria:

• Class III/IV lupus nephritis that was treated with induction therapy within the 6 months prior to Screening.
• Active neuropsychiatric SLE (excluding lupus headache) within the 6 months prior to Screening.
• SLE overlap syndromes including, but not limited to, rheumatoid arthritis, systemic sclerosis, polymyositis, dermatomyositis, or mixed connective tissue disease (Sjögren's syndrome is permitted).
• Antiphospholipid syndrome and prior unprovoked venous or arterial thrombosis who are not on stable and adequate anticoagulation.
• Two or more episodes of herpes zoster, or one or more episodes of disseminated herpes zoster or herpes zoster ophthalmicus.
• History of malignancy, except for successfully treated non-melanoma skin cancer or localized carcinoma in situ of the cervix.
• Pregnancy, breastfeeding, or considering becoming pregnant during the study.
• Clinically relevant or significant ECG abnormalities at Screening.
• Planned elective surgery that would impact study procedures or assessments through the completion of the Week 52 assessments.

NOTE: Other protocol defined Inclusion/Exclusion criteria may apply.