1. Male and female participants aged 12 years or older at the time of screening, or limited to 18 years or older in European Economic Area countries and other countries where inclusion of participants below 18 years is not allowed.
2. Diagnosis of systemic lupus erythematosus meeting the 2019 European League Against Rheumatism/American College of Rheumatology (EULAR/ACR) SLE classification criteria at least 6 months prior to screening.
3. Elevated serum titers at screening of anti-nuclear antibodies ≥ 1:80 as determined by a central laboratory with a SLE-typical fluorescence pattern.
4. Currently receiving CS and/or anti-malarial treatment and/or another disease-modifying antirheumatic drug (DMARD) as specified in the protocol.
5. SLEDAI-2K criteria at screening: SLEDAI-2K score ≥ 6 points, excluding points attributed to "fever", "lupus headache", "alopecia", and "organic brain syndrome"
6. BILAG-2004 disease activity level at screening of at least 1 of the following:

a) BILAG-2004 level 'A' disease in greater than or equal to 1 organ system, Or

b) BILAG-2004 level 'B' disease in greater than or equal to 2 organ systems

1. Weigh at least 35 kg at screening

1. Prior treatment with ianalumab
2. History of receiving following treatment I) high dose CS, calcineurin inhibitors, JAK or other kinase inhibitors or other DMARD (except as listed in inclusion criteria) administered within 12 weeks prior to screening II) cyclophosphamide or biologics such as immunoglobulins (intravenous or s.c.), plasmapheresis, anti-type I interferon receptor biologic agents, anti-CD40 agents, CTLA4-Fc Ig or B-cell activating factor (BAFF)-targeting agents administered within 24 weeks prior to screening; belimumab administered within 12 weeks prior to screening. III) any B cell-depleting therapies, other than ianalumab administered within 36 weeks prior to randomization or as long as B cell count is less than the lower limit of normal or baseline value prior to receipt of B cell-depleting therapy (whichever is lower). IV) Traditional Chinese medicines administered within 30 days prior to randomization
3. Active viral, bacterial or other infections requiring intravenous or intramuscular treatment for clinically significant infection
4. Chronic infection with hepatitis B virus (HBV) or hepatitis C virus (HCV)
5. Evidence of active tuberculosis infection
6. History of primary or secondary immunodeficiency, including a positive human immunodeficiency virus (HIV) test result at screening

Other Protocol defined exclusion criteria may apply.