In this phase 3, multicenter, randomized, double-blind, placebo-controlled trial, patients with SLE on SOC therapy were assigned to receive placebo, or belimumab 1 or 10 mg/kg by intravenous (IV) infusion over 1 hour on days 0, 14, and 28, and every 28 days through week 72. While the initiation of an immunosuppressive (IS) drug was prohibited during the trial, the addition of a new antimalarial (AM) drug and dose increases of concomitant IS or AM drugs were permitted until week 16. After week 16, however, the maximum doses of IS or AM drugs could be no greater than the higher of the baseline or week-16 dose. For corticosteroids, any dose was permitted through week 24; thereafter through week 44, the dose had to be within 25% or 5 mg of baseline. Between weeks 44 and 52, no increase over the higher of the baseline or week-44 dose was permitted. From weeks 52 through 68, the dose had to be within 25% or 5 mg of baseline, and an increase over the higher of the baseline or week-68 dose was prohibited after week 68. Prednisone could be reduced at the discretion of the investigator. As in the companion phase 3 BLISS-52 trial, the addition of a new biologic agent at any time, an inhibitor of the renin-angiotensin system after 4 months, or a new 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitor after 6 months was prohibited; other antihypertensive or lipid-lowering agents were allowed during the study (17 (link)). The Safety of Estrogens in Lupus Erythematosus National Assessment–SLE Disease Activity Index (SELENA-SLEDAI) (18 (link)), Physician’s Global Assessment (PGA) (18 (link)), British Isles Lupus Assessment Group (BILAG) (19 (link),20 (link)), and SLE Flare Index (SFI) (21 (link)) were evaluated every 4 weeks (except weeks 56 and 64), as were AEs, vital signs, concomitant medications, and laboratory and pregnancy tests.