Siltuximab, a Novel Anti-Interleukin-6 Monoclonal Antibody, for Castleman's Disease

Purpose Interleukin-6 (IL-6) has emerged as a key factor in the pathogenesis of the atypical lymphoproliferative disorder Castleman's disease (CD). Siltuximab is a new anti-IL-6, chimeric monoclonal antibody with potential therapeutic benefit in patients with CD. Methods We report interim results from an open-label, dose-finding, seven-cohort, phase I study in which patients with symptomatic, multicentric or unresectable, unicentric CD received siltuximab at 1-, 2-, or 3-week intervals. The main efficacy end point of clinical benefit response (CBR) was defined as a composite of clinical and laboratory measures relevant to the management of CD. In addition, radiologic response was independently assessed by using modified Cheson criteria. Results Eighteen (78%) of 23 patients (95% CI, 56% to 93%) achieved CBR, and 12 patients (52%) demonstrated objective tumor response. All 11 patients (95% CI, 72% to 100%) treated with the highest dose of 12 mg/kg achieved CBR, and eight patients (73%) achieved objective tumor response. Overall objective-response duration ranged from 44 to >= 889 days, and one patient had complete response for >= 318 days. Hemoglobin increased markedly in 19 patients (median increase, 2.1 g/dL; range, 0.2 to 4.7 g/dL) in the absence of transfusion or erythropoiesis-stimulating agents. No dose-limiting toxicity was reported, and only three patients had grade 3 or higher adverse events after a median exposure of 331 days (range, 1 to 1,148 days). Conclusion These interim results strongly suggest that siltuximab is an effective treatment with favorable safety for the management of CD. An additional study is planned to fully evaluate safety and efficacy at the recommended dose of 12 mg/kg every 3 weeks. J Clin Oncol 28: 3701-3708. (C) 2010 by American Society of Clinical Oncology