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Blockade of α4β7 receptors on T-lymphocytes has been shown to occur for several weeks after a single dose of vedolizumab. The drug concentration following the infusion has been shown to be dose related with a mean maximum concentration of 12.5 μg/mL in those receiving 0.5 mg/kg of vedolizumab and 52.0 μg/mL in those receiving 2 mg/kg. The serum half-life of these two doses is 9-12 days respectively and saturation of α4β7 receptors on T-lymphocytes is >90% at both 4-6 weeks following infusion. In a dose ranging study, the serum drug concentrations increase with increasing dose and when regular induction infusions are used (on day 1, 15, 29 and 85), the serum half-life is between 15 and 22 days across all groups^[1].