Differences in the incidence of flares or new onset of inflammatory bowel diseases in patients with ankylosing spondylitis exposed to therapy with anti-tumor necrosis factor α agents

Objective. Ankylosing spondylitis (AS) and inflammatory bowel disease (IBD) are clinically and pathologically linked. Anti-tumor necrosis factor (anti-TNF) agents are efficacious in treating AS, but not all are equally effective in treating IBD (Crohn's disease [CD] and ulcerative colitis [UC]). The purpose our study was to analyze the incidence of flares and new onset of IBD in patients with AS treated with anti-TNF agents. Methods. Data from 9 trials, 7 placebo-controlled trials and 2 open studies, were analyzed. Results. Data were available on 419 AS patients exposed to etanercept (625 patient-years), 366 exposed to infliximab (618 patient-years), 295 exposed to adalimumab (132 patient-years), and 434 placebo patients (150 patient-years). A history of IBD was reported in 76 of 1,130 patients (6.7%). There were 2 reports of TBD while receiving placebo (1.3 per 100 patient-years), 1 while receiving infliximab, and 3 while receiving adalimumab. Among the 14 IBD cases receiving etanercept (2.2 per 100 patient-years) there were 8 CD and 6 UC cases, significantly different from infliximab (P = 0.01) but not from placebo. Patients with a history of IBD had an IBD flare odds ratio of 18.0 (95% confidence interval [95% CI] 2-154) while taking etanercept and 4.2 (95% CI 0.4-44) while taking adalimumab, in comparison with infliximab. The incidence rates of new onset of IBD showed no significant difference between etanercept (0.8 per 100 patient-years) and placebo (0.5 per 100 patient-years). Conclusion. New onset and flare of IBD are infrequent events in AS patients receiving anti-TNF therapy. Infliximab (but not etanercept) largely prevents IBD activity. More data are required for adalimumab. The incidence of new onset of IBD was statistically not different from placebo for all anti-TNF agents.