Inclusion Criteria:  Are diagnosed with SLE at least 24 weeks before Day 1 of study Have documentation of having a score of 10 or more points on the European League Against Rheumatism (EULAR)/American College of Rheumatology (ACR) 2019 classification criteria for SLE Have a SLEDAI-2K score ≥6 at screening (Day 1) and clinical Systemic Lupus Erythematosus Disease Activity Index 2000 (SLEDAI-2K) score ≥4 (not including any items related to laboratory values) at randomization (Day 2) Must be receiving at least 1 background standard-of-care medication for SLE  Exclusion Criteria:  Participants are excluded if they have received any of the following medications or therapies within the indicated timeframe prior to the randomization visit (Day 2). Are currently receiving oral corticosteroids at doses >20 mg per day of prednisone (or equivalent) or have adjusted the dosage of corticosteroids within 2 weeks before starting study treatment Have received parenteral corticosteroids within 12 weeks before starting study treatment or are expected to require parenteral corticosteroids during the study Have a current or recent acute, active infection Have had a serious, chronic, recurring conditions of herpes simplex, herpes zoster, recurring cellulitis, chronic osteomyelitis) Have human immunodeficiency virus (HIV) infection, hepatitis B virus (HBV), hepatitis C infection (HCV), active tuberculosis (TB) Have active fibromyalgia or active occurrence of an inflammatory condition that, in the investigator's opinion, would make it difficult to appropriately assess SLE activity for the purposes of this study Have experienced a cardiac event within 24 weeks to 12 months prior to screening Have a history of clinically significant or uncontrolled illness that in the opinion of the investigator could put the participant at risk to participate in the study Are, in the judgment of the investigator, actively suicidal and therefore deemed to be at significant risk for suicide Are pregnant or are intending to become pregnant or to breastfeed at any time in the study