Investigator-initiated, multi-center, single-arm, open-label study of the effectiveness of canakinumab in Japanese patients with Schnitzler syndrome

Schnitzler syndrome is an adult-onset autoinflammatory disease characterized by an urticaria-like rash and monoclonal gammopathy with fever and fatigue. Although some treatments have shown efficacy in clinical trials, no approved treatment exists. We aimed to assess canakinumab, an anti-IL-1β monoclonal antibody, in Japanese patients. This phase II, multicenter, single-arm, open-label study enrolled five patients with active disease from four hospitals. Patients received a single subcutaneous dose of canakinumab 150 mg. The primary endpoint was the proportion of patients achieving a complete clinical response (CR), based on physician global assessment on Day 7. If a CR was not achieved on Day 7 or by 8 weeks post-treatment, the dose was increased to 300 mg. Dosing continued every 8 weeks until 24 weeks. The study also evaluated patient-reported disease activity and changes in acute inflammatory markers, including white blood cell count, neutrophil count, C-reactive protein concentration, and serum amyloid A level. Quality of life was assessed using the Dermatology Life Quality Index and the 36-item Short Form health survey. Safety was also evaluated. Sixty percent (3/5) of patients had a CR on Day 7. One of the remaining two patients had a CR 7 days after the dose was increased to 300 mg. All five patients, including those who did not achieve a CR, showed improvement in inflammatory markers and quality of life scores, and no new adverse events were detected. In this trial, canakinumab showed a potential for usefulness in Japanese patients with Schnitzler syndrome.