Siltuximab in relapsed/refractory multicentric Castleman disease: Experience of the Italian NPP program

Because of the rarity of the disease, randomized clinical trials for multicentric Castleman disease (MCD) remain a challenge and, as a consequence, there is no established standard of care. Siltuximab is a chimeric immunoglobulin G1κ monoclonal antibody against human IL-6 which was recently approved by FDA. Eligible patients in Italy were granted early access through a Named Patient Program (NPP). The aim of this observational multicenter retrospective study was to analyze outcomes and toxicity data of relapsed or refractory MCD patients treated with siltuximab in a real life context. All the 9 patients who received siltuximab in Italy under the NPP were enrolled. Median duration of treatment was 285 days (range, 104-1113 days). The global overall response rate was 33.3%. At the time of this analysis, none of the 3 responder patients had subsequently disease relapse: response duration was 20, 23, and 37 months, respectively. Grade 1 to 2 fatigue and pruritus were observed in 2 (22.2%) patients, and weight gain was reported in only 1 patient (grade 1); local edema was reported in 2 patients with a grade 2 presentation. The most common side effect was upper respiratory tract infection reported in 3 (33.3%) patients but in these cases was grades 1 to 2. No patient developed an infusion-related reaction. Our NPP data support siltuximab as single agent in the real-life experience of the treatment of relapse/refractory MCD patients in effectiveness, safety profile, and sustained disease control.