Abstract

Objective Semapimod, a small molecule known to inhibit proinflammatory cytokine activity, was studied to determine the optimal dose necessary to achieve a response in patients with moderate to severe Crohn's disease (CD).

Methods A randomised, double-blind, placebo-controlled trial (CD04) was carried out followed by an open-label extension study (CD05). The trial was conducted in international multicentre outpatient clinics and included patients with moderate to severe CD (Crohn's Disease Activity Index (CDAI) 250–400). Placebo was administered for 3 days; 60 mg semapimod intravenously for 1 day with placebo for 2 days; or 60 mg semapimod intravenously for 3 days. Participants who completed CD04 could participate in the open-label extension study, CD05, to receive up to five additional semapimod HCl 60 mg daily doses three times every 6–8 weeks. The main outcome measures were CDAI, Inflammatory Bowel Disease Questionnaire (IBDQ), Crohn's Disease Endoscopic Inflammation Score (CDEIS) and serum C-reactive protein (CRP) concentration.

Results 152 patients were randomised in CD04. Responses for 1 and 3 day regimens were similar to placebo for CDAI (p=0.82), IBDQ (p=0.85), CDEIS (p=0.57) and CRP (p=0.40). The only noteworthy treatment-related safety finding was infusion reaction (phlebitis): 7.3, 34.8 and 62.7% for the placebo and 1 and 3 day semapimod treatment groups, respectively (p<0.001). In the open-label CD05 study (included=119 patients) a posthoc analysis showed that the mean CDAI improved in patients receiving 6 compared with ≤3 cumulative doses (204.1±83 vs 251.4±103.05, p=0.006).

Conclusions Single and 3 day dosing of semapimod (≤180 mg) was ineffective for the treatment of moderate to severe CD. However, cumulative dosing ≥360 mg was associated with decreased CDAI in a limited number of patients.