A Pilot Randomized Trial of a Human Anti-interleukin-6 Receptor Monoclonal Antibody in Active Crohn's Disease

Background & Aims: Interleukin-6 (IL-6) regulates immune response and inflammation. We carried out a pilot placebo-controlled study to investigate the efficacy, pharmacokinetics, and safety of MRA, a humanized monoclonal antibody to IL-6 receptor, in patients with active Crohn's disease.

Methods: Thirty-six patients with active Crohn's disease (Crohn's Disease Activity Index [CDAI] > or =150) were randomly assigned to receive biweekly intravenous infusion of either placebo, MRA, or MRA/placebo alternately for 12 weeks at a dose of 8 mg/kg. The study's primary end point was a clinical response rate that was defined as a reduction of CDAI > or =70.

Results: At the final evaluation, 80% of the patients (8 of 10) given biweekly MRA had a clinical response as compared with 31% of the placebo-treated patients (4 of 13; P = 0.019). Twenty percent of the patients (2 of 10) on this regimen went into remission (CDAI <150), as compared with 0% of the placebo-treated patients (0 of 13). The clinical response rate of the every-4-week regimen was 42% (5 of 12). The serum concentrations of MRA were detected at 2 weeks after every infusion, at which time acute phase responses were completely suppressed; however, they were not suppressed at 4 weeks. Endoscopic and histologic examination showed no difference between MRA and placebo groups. The incidence of adverse events was similar in all the groups.

Conclusions: This is the first clinical trial of humanized anti-IL-6 receptor monoclonal antibody in Crohn's disease. A biweekly 8 mg/kg infusion of MRA was well tolerated, normalized the acute-phase responses, and suggests a clinical effect in active Crohn's disease.