Real-world data of siltuximab for Chinese patients with iMCD: combination with BCD regimen as a potential approach for severe cases.

Idiopathic multicentric Castleman disease (iMCD) is a rare disease characterized by polyclonal lymphoproliferation and systemic inflammation. Siltuximab, targeting interleukin-6 (IL-6), has been recommended as the first-line therapy for iMCD. However, substantial real-world data from China were still lacking, and treatment for patients with severe iMCD remained challenging. This single-center retrospective study investigated the real-world efficacy and safety of siltuximab-based therapy in 43 consecutive patients with iMCD in China from July 2022 to March 2024. The overall response rate (including symptomatic and biochemical response) was 59% at week 3 and increased to 91% at week 12, with complete and partial response rates of 54% and 37%, respectively. Patients who received siltuximab as a first-line treatment exhibited better treatment response (OR = 0·040, 95% CI, 0·004 - 0·390, p = 0·006). Inflammatory markers (such as interleukin-6 and high-sensitivity C-reactive protein [hsCRP]) and pathologic types showed no predictive role in the treatment responses. Eighteen patients, who were all classified as severe iMCD, received combined therapy of siltuximab and BCD regimen (bortezomib, cyclophosphamide and dexamethasone). Of them, the overall response rate was 50% at week 3, which increased to 100% at week 12. Our findings reinforced the existing evidence on the efficacy and safety of siltuximab and highlighted the potential benefits of combining siltuximab with BCD regimen in severe iMCD patients.