Objectives: Schnitzler syndrome (SchS) is a rare autoinflammatory disease characterised by a primary pathogenic involvement of interleukin (IL)-1. Therefore, IL-1 blockers are currently considered the optimal therapeutic option for SchS patients. However, while IL-1 blockers are first-line for SchS, long-term real-world evidence is limited by the rarity of the disease. We assessed the long-term effectiveness and safety of the IL-1 inhibitors anakinra and canakinumab used in SchS, also looking for variables capable of affecting global effectiveness and drug retention over time.
Methods: Data analysed in this study were drawn from the international AutoInflammatory Disease Alliance (AIDA) Registry dedicated to SchS.
Results: 28 SchS patients corresponding to 37 treatment lines were included in the study. Complete and partial responses occurred in 73.1% and 29.9% of anakinra-treated patients, and 66.8% and 33.3% with canakinumab. The overall anakinra and canakinumab drug retention rates at 12-, 36-, and 60-month follow-up were 85.6%, 81.7% and 64.7%, respectively; the probability of discontinuing IL-1 inhibitors at 12-, 36- and 60 months due to loss of effectiveness was 9.6%, 13.7% and 24.5%, respectively. The maximum IgG M-protein levels were found to be significantly higher in patients achieving partial response compared to those benefiting from complete response (p=0.032). Lymphadenopathy independently predicted anti-IL-1 discontinuation due to loss of effectiveness (HR 7.78, 95% CI: 1.27-47.9; p=0.027).
Conclusions: The present study confirms the high effectiveness of IL-1 inhibitors in controlling SchS, including the complete and partial response rates and the long-term survival. Elevated IgG M-protein levels and the presence of lymphadenopathy should be considered as potential indicators for identifying patients more likely to exhibit a partial response and a possible loss of treatment efficacy.