• Participants who are age 12 to \<18 years at the time of randomization

• Participants who are age 5 to \<12 years (younger participant cohort) at the time of randomization once recruitment is open. (Investigators will be notified by the Sponsor when recruitment is open to this younger population)

• International Society of Nephrology and the Renal Pathology Society (ISN/RPS) 2003 Class III or IV active LN demonstrated on renal biopsy performed in the 12 months prior to or during screening

• Class V disease may be present in addition to Class III or IV LN, but participants with isolated Class V disease are not eligible

• Diagnosis of SLE according to the Systemic Lupus International Collaborating Clinics (SLICC) 2012 criteria

• Significant proteinuria defined by a UPCR above \> 0.5 based on a first-morning void (FMV) collection at screening

• During the 12 months prior to or during screening, all participants must have received at least one dose of pulse-range IV methylprednisolone (typically 30 mg/kg, maximum of 1000 mg per dose) or equivalent for the treatment of the current episode of active LN.