Rapcabtagene Autoleucel for Lupus Nephritis or SLE

Key Inclusion Criteria: * Men and women with SLE, aged \>= 18 years and =\< 75 years at screening, fulfilling the 2019 European League Against Rheumatism (EULAR)/American College of Rheumatology (ACR) classification criteria for SLE at screening. * Participant must be positive for at least one of the following autoantibodies at screening: antinuclear antibodies (ANA) at a titer of \>= 1:80 (on HEp-2 cells or an equivalent positive test), or anti-dsDNA (above the ULN); or anti-Sm (above the ULN) as determined by a central laboratory. * Active lupus nephritis without signs of significant chronicity or active systemic lupus erythematosus * SLEDAI-2K Criteria at screening: SLEDAI-2K score \>= 6 points (Gladman et al 2002, Touma et al 2011), excluding points attributed to "fever", "lupus headache", "alopecia", and "organic brain syndrome". * Inadequate response at screening to at least two therapies Key Exclusion Criteria: * Any acute, severe lupus related-flare at screening that needs immediate treatment other than pulse GCs and/or makes the immunosuppressive washout impossible and, thus, makes the participant ineligible for CD19 CAR-T therapy * Inadequate organ function during screening and prior to randomization * History or current diagnosis of ECG or cardiac abnormalities indicating significant risk of safety for participants prior to randomization * Human immunodeficiency virus (HIV) positivity at screening. * Acute or chronic infection with hepatitis B (HBV) or hepatitis C (HCV) at screening. * Grade 2 or higher thromboembolic event in the past 4 weeks prior to screening. Other protocol-defined inclusion/exclusion criteria may apply.