Table 1.

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.