Efficacy and safety of orelabrutinib in relapsed/refractory idiopathic multicentric Castleman disease: A single‐centre, retrospective study

Summary Idiopathic multicentric Castleman disease (iMCD) is a rare and heterogeneous lymphoproliferative disorder that lacks standardised treatment options for patients with refractory or relapsed (r/r) disease. Blocking Bruton's tyrosine kinase (BTK) has emerged as a promising therapeutic approach for iMCD without depleting B cells. This single‐centre, retrospective study enrolled 10 patients with r/r iMCD who were treated with orelabrutinib, a novel, next‐generation BTK inhibitor. The median age at orelabrutinib initiation was 48 (range: 31–58) years. The overall response rate was 70% (7/10 patients, 95% CI: 34.8–93.3), with 20% ( n = 2) achieving complete response and 50% ( n = 5) achieving partial response. The median time to response was 9.8 (range: 5.9–20.5) months. Patients in the non‐responder group also demonstrated a continuous improvement in haemoglobin (91–105 g/L) and albumin (32–38 g/L) levels at month 12 of treatment despite not fulfilling response criteria. No grade 3 or higher adverse events occurred during the median time to the next treatment of 29.0 (range: 15.0–36.2) months. No patient mortality was recorded during the median follow‐up duration of 32.8 (range: 15.0–36.9) months. In conclusion, orelabrutinib is a safe and effective regimen for r/r iMCD.