Adalimumab treatment in Crohn’s disease: an overview of long-term efficacy and safety in light of the EXTEND trial

The advent of anti-tumor necrosis factor (TNF) therapies revolutionized the treatment of inflammatory bowel disease. Adalimumab is a subcutaneous anti-TNF agent indicated for use in patients with moderate-to-severe Crohn's disease and those with moderate-to-severe ulcerative colitis. In both diseases, it can be used for both induction of remission and for maintenance of remission. This review focuses on its use in Crohn's disease as described in the EXTEND (Extend the Safety and Efficacy of Adalimumab through Endoscopic Healing) trial. Several clinical trials using traditional instruments to measure clinical response have had endoscopic substudies looking for endoscopic healing. The EXTEND trial is the first to use mucosal healing on endoscopy as a primary endpoint for patients with moderate-to-severe Crohn's disease and baseline ulcerative disease treated with continuous adalimumab. In this well designed trial, the primary endpoint was narrowly missed, but the secondary endpoints further the notion that mucosal healing should be a more mainstream measure of drug efficacy. How this will translate from clinical trials to the clinic is not yet clear, but identifying noninvasive markers for mucosal healing, and understanding the implications of mucosal healing for safety, resource utilization, and quality of life are all worthy targets for further study. The aim of this review is to understand the role of mucosal healing, safety profile, and efficacy in patients treated with anti-TNF therapy, with particular attention to adalimumab and the EXTEND trial.