Exclusive antagonism of the α4β7 integrin by vedolizumab confirms the gut-selectivity of this pathway in primates

Background: Biological therapies that antagonize specific molecules have demonstrated efficacy in inflammatory bowel diseases, but infections resulting from systemic immunosuppression underscore the need for safer therapies. The objective of this investigation was to determine if antagonism of the a4 beta 7 integrin would exclusively yield gut-selective antiinflammatory activity in primates. Methods: A series of experiments were conducted to investigate potential intra- and extraintestinal effects in healthy nonhuman primates dosed repeatedly with the a4 beta 7-exclusive antagonist vedolizumab (former versions: MLN0002, MLN02, LDP-02) for 4, 13, and 26 weeks. Results: No adverse clinical effects of vedolizumab were observed in healthy cynomolgus monkeys up to the highest doses tested (100 mg/kg). Histomorphologic analyses indicated a reduction in the frequency of leukocytes in gastrointestinal tissue, but not other organs. A significant (P < 0.05) decrease in the frequency of beta?7+ lymphocytes in gastrointestinal tissues corresponded to a significant (P < 0.05) increase in a4 beta?7+ memory helper T lymphocytes in peripheral blood. This elevation was specific to a4 beta?7+ memory helper T lymphocytes; levels of other leukocyte subsets remained unaffected. Systemic opportunistic infections were not observed, and vedolizumab did not inhibit adaptive or innate immune responses systemically. Conclusions: These data demonstrate that blocking the a4 beta 7 integrin exclusively yields gut-selective antiinflammatory activity in primates. (Inflamm Bowel Dis 2012;)