The cryopyrin-associated periodic syndrome (CAPS) is a rare inherited inflammatory disease associated with overproduction of interleukin-1. Canakinumab is a human anti–interleukin-1β monoclonal antibody.

We performed a three-part, 48-week, double-blind, placebo-controlled, randomized withdrawal study of canakinumab in patients with CAPS. In part 1, 35 patients received 150 mg of canakinumab subcutaneously. Those with a complete response to treatment entered part 2 and were randomly assigned to receive either 150 mg of canakinumab or placebo every 8 weeks for up to 24 weeks. After the completion of part 2 or at the time of relapse, whichever occurred first, patients proceeded to part 3 and received at least two more doses of canakinumab. We evaluated therapeutic responses using disease-activity scores and analysis of levels of C-reactive protein (CRP) and serum amyloid A protein (SAA).

In part 1 of the study, 34 of the 35 patients (97%) had a complete response to canakinumab. Of these patients, 31 entered part 2, and all 15 patients receiving canakinumab remained in remission. Disease flares occurred in 13 of the 16 patients (81%) receiving placebo (P<0.001). At the end of part 2, median CRP and SAA values were normal (<10 mg per liter for both measures) in patients receiving canakinumab but were elevated in those receiving placebo (P<0.001 and P=0.002, respectively). Of the 31 patients, 28 (90%) completed part 3 in remission. In part 2, the incidence of suspected infections was greater in the canakinumab group than in the placebo group (P=0.03). Two serious adverse events occurred during treatment with canakinumab: one case of urosepsis and an episode of vertigo.

Treatment with subcutaneous canakinumab once every 8 weeks was associated with a rapid remission of symptoms in most patients with CAPS. (ClinicalTrials.gov number, NCT00465985.)