On day 0 eligible subjects will receive a loading dose of two subcutaneous (S.C.) injections of rilonacept for a total of 320 mg. Subsequent study drug injections of rilonacept 160 mg will be administered once a week for four weeks. After subjects complete this initial 4-week treatment phase, they will be eligible to receive rilonacept 160 mg once weekly for 48 weeks during the extended treatment phase.