On April 22, 2014, the FDA granted full approval to siltuximab (SYLVANT for 
injection; Janssen Biotech, Inc.), a chimeric human-mouse monoclonal antibody to 
IL6, for the treatment of patients with multicentric Castleman disease (MCD) who 
are human immunodeficiency virus (HIV) negative and human herpesvirus-8 (HHV-8) 
negative. The approval was primarily based on the results of a randomized, 
double-blind trial in which 79 symptomatic patients with MCD were allocated 
(2:1) to siltuximab plus best supportive care (BSC) or to placebo plus BSC. The 
primary efficacy endpoint was the proportion of patients in each arm achieving a 
durable tumor and symptomatic response that persisted for a minimum of 18 weeks 
without treatment failure. Tumor response was based on independent review of CT 
scans using the revised Response Criteria for Malignant Lymphoma, and 
symptomatic response was defined as complete resolution or stabilization of 34 
MCD-related signs and symptoms as reported by the investigator. Thirty-four 
percent of patients in the siltuximab arm and no patients in the placebo arm met 
the primary endpoint (P = 0.0012). The most common adverse reactions (>10% 
compared with placebo) during treatment with siltuximab were pruritus, increased 
weight, rash, hyperuricemia, and upper respiratory tract infection.