Safety and tolerability of concurrent natalizumab treatment for patients with Crohn's disease not in remission while receiving infliximab.

Background: Natalizumab, a humanized monoclonal IgG(4) antibody to alpha4 integrin, was investigated as a treatment of active Crohn's disease (CD). The safety of natalizumab given in combination with infliximab has not previously been studied.

Methods: Seventy-nine adult patients with active CD (Crohn's Disease Activity Index [CDAI] score > or = 150) despite ongoing infliximab treatment were randomized 2:1 to receive 3 intravenous infusions of natalizumab (300 mg; n = 52) or placebo (n = 27) every 4 weeks.