Objective. To evaluate the efficacy and safety of the interleukin-1 inhibitor rilonacept (interleukin-1 Trap) for gout flare prevention during initiation of uric acid-lowering therapy (ULT). Methods. In total, 241 adult patients with gout, >2 gout flares within the past year, and a serum urate level >7.5 mg/dl were initiated on allopurinol 300 mg daily and randomly allocated in a 1:1:1 ratio to receive 16 once-weekly subcutaneous injections of placebo, rilonacept 80 mg, or rilonacept 160 mg, with a double (loading) dose on day 1. Allopurinol was titrated to achieve a serum urate level of <6.0 mg/dl. The study was powered for the primary efficacy end point, the number of gout flares per patient through week 16.