Clinical Course of Schnitzler Syndrome in Japan: Comparison Between Existing Treatments and Post-Canakinumab Administration

Abstract

　Schnitzler syndrome (SchS) is a rare acquired autoinflammatory disease characterized by urticarial-like rash and monoclonal IgM (rarely IgG) gammopathy. A placebo-controlled double-blind trial conducted in Germany demonstrated the efficacy of canakinumab in treating SchS. Based on these findings, we conducted a Phase II trial (SCan trial) targeting Japanese patients with SchS and reported the clinical utility of canakinumab in Japanese SchS patients using data from the first 24 weeks (Period I) after an initial dose of 150 mg. However, due to the limited number of cases in Japan, the SCan trial was conducted as a single-arm, open-label study. Therefore, it was necessary to demonstrate that the sustained stabilization of clinical symptoms and laboratory findings observed in this trial was not present before canakinumab administration and that inflammation frequently relapsed under conventional treatments. To clarify this, we examined the pre-treatment clinical course of the five patients enrolled in the SCan trial. Our analysis revealed that none of the patients achieved sustained remission under either no treatment or conventional therapy, and all experienced repeated symptom relapses. These results strongly support that the clinical benefits of canakinumab were not coincidental but rather demonstrate its efficacy in SchS treatment.