Objective The α₄β₇ integrin monoclonal antibody vedolizumab is hypothesised to be gut selective. Effects of vedolizumab on immune responses to parenterally or enterally administered antigens were investigated.

Design In this randomised, double-blind, placebo-controlled, phase I trial, healthy participants received a single intravenous dose of vedolizumab 750 mg (n=64) or placebo (n=63). After 4 days, participants began intramuscular hepatitis B vaccine (HBV; days 4, 32, 60) and oral cholera vaccine (OCV; days 4, 18) regimens. The study was designed to demonstrate a 15% non-inferiority margin for the between-group difference in the primary end point: percentage of participants with HBV seroconversion at day 74 (serum hepatitis B surface antigen (HBs) antibody titre ≥10 IU/L). OCV seroconversion at day 74 (>4-fold increase in serum cholera toxin (CT) antibodies) was a secondary end point.

Results A total of 56 (90.3%) placebo-treated and 54 (88.5%) vedolizumab-treated participants responded to HBV. Geometric mean anti-HBs titres were similar for placebo (114.4 IU/L) and vedolizumab (129.6 IU/L) at day 74. A total of 60 (96.8%) placebo-treated and 52 (82.5%) vedolizumab-treated participants responded to OCV at day 74. Geometric mean anti-CT IgG levels were higher for placebo than for vedolizumab at day 74 (9210.08 vs 3007.8 ELISA Units (EU)/mL) and day 32 (11629.3 vs 1575.4 EU/mL). Anti-CT IgA results were similar. Adverse events were consistent with previous experience. One serious adverse event (spontaneous abortion) was reported for placebo.

Conclusions Vedolizumab did not alter the response to parenterally administered antigens but reduced the response to oral antigens, demonstrating its gut-selective mechanism of action.

Trial registration number NCT Number: 01981616; EudraCT Number: 2011-001874-24.