Study treatment arms
| Treatment | Arm A (control) | Arm B (combination) | Arm C (reference) |
| Belimumab | Belimumab SC 200 mg/week for 52 weeks | Belimumab SC 200 mg/week for 52 weeks | Belimumab SC 200 mg/week plus SoC for 104 weeks |
| Rituximab or matched placebo | One cycle of placebo intravenously (rituximab-matched) at week 4 and week 6 | One cycle of rituximab intravenously 1000 mg at week 4 and week 6 | None |
| Premedication (30 min before each placebo or rituximab infusion) | Methylprednisolone intravenously 100 mg or equivalent, oral antihistamine, acetaminophen or equivalent | Methylprednisolone intravenously 100 mg or equivalent, oral antihistamine, acetaminophen or equivalent | None |
| Post week 52 therapy | Antimalarials, NSAIDs and/or corticosteroids with a prednisone equivalent dose of ≤5 mg/day | Antimalarials, NSAIDs and/or corticosteroids with a prednisone equivalent dose of ≤5 mg/day | Continue belimumab SC 200 mg/week plus SoC* |
↵*Patients in arm C are allowed to receive rescue therapy if, in the opinion of the investigator, they require additional treatment. This can include corticosteroids at >5 mg/day prednisone equivalent.
NSAIDs, non-steroidal anti-inflammatory drugs; SC, subcutaneous; SoC, standard of care.