Restoration of Health with Siltuximab in Multicentric Castleman Disease
Siltuximab, a monoclonal antibody against IL-6, was recently approved in the United States and in Europe for the treatment of adults with MCD who are HIV-negative and HHV-8–negative. Information on MCD’s symptoms, functioning, and well-being was gathered in a pivotal global registration study in the MCD2001 study (van Rhee F, et al. Lancet Oncol. 2014;15:966-974), with a general patient-reported outcomes questionnaire—the Short Form-36 (SF-36, acute version 2)—and other patient-reported outcomes measures. At ASH 2014, van Rhee and colleagues reported on the longitudinal impact of siltuximab on symptoms, functioning, and well-being as measured by the SF-36 compared with placebo (van Rhee F, et al. Blood. 2014;124. Abstract 4469).
MCD2001 was a randomized (2:1), double-blind, placebo-controlled, multicenter study to determine the safety and efficacy of siltuximab in 79 patients with symptomatic MCD. Patients received siltuximab 11 mg/kg or placebo every 3 weeks in combination with best supportive care. Patients completed the SF-36 at baseline and every 3 weeks throughout the treatment period. Patients, whose baseline SF-36 domain scores were below the general population norm for their age-group (N = 46), were included in an analysis to compare by treatment arm the proportion of patients achieving an SF-36 domain score that was greater than or equal to the population norm at their final visit.
At baseline, the population demonstrated inferior health compared with the general population across all SF-36 domains. The odds of the siltuximab-treated patients reaching a return to the general population health norms versus patients receiving placebo in the vitality, role-emotional, and social function domains were significant, with odds ratios of 5.3 (P = .049), 5.5 (P = .011), and 11.4 (P = .014), respectively. A positive health trend was observed for patients who received siltuximab compared with placebo across all other domains, particularly role-physical (5.5; P = .067).
These results showed that patients with MCD reported notably inferior health compared with the general population at baseline, but that treatment with siltuximab significantly improved the odds for return to the general population health norms versus placebo in the role-emotional, vitality, and social function domains, as well as demonstrated a trend to improve health across all other SF-36 domains among patients with MCD who were below the norms at baseline. These data show that a clinically relevant patient-reported outcomes benefit for physical and mental health was observed with siltuximab, which supports the “disease control” treatment goal for this agent.