Clinical Information

Vedolizumab (Entyvio) is a humanized IgG1 kappa monoclonal antibody directed against integrin alpha-4 beta-7. Blocking the alpha-4 beta-7 integrin results in a gut-selective anti-inflammatory response.(1) The drug is US Food and Drug Administration-approved for the treatment of adult patients with moderately to severely active ulcerative colitis or Crohn disease. The main indication for therapeutic drug monitoring of vedolizumab is in the setting of primary nonresponse or loss-of-response to therapy, also called reactive monitoring.(2-10) Vedolizumab trough concentrations greater than 12 mcg/mL to 15 mcg/mL have been associated with clinical or endoscopic remission.(3,5,11) Proactive monitoring of vedolizumab concentrations has been proposed, but there is not sufficient data to support routine proactive testing at this time. Therapeutic drug monitoring of biologics is usually carried out by measuring the monoclonal antibody therapy concentration and assessing its immunogenicity or the appearance of anti-drug antibodies. Some patients on vedolizumab may develop antibodies to vedolizumab (ATV) over time. In clinical trials, approximately 4% of patients treated with vedolizumab were positive for ATV at any time and 1% or less were persistently positive. Clinically significant ATV impact drug clearance and a positive ATV is associated with lower trough concentrations of vedolizumab.