A recent observational study (N Williet et al. Clin Gastroenterol Hepatol 2017; 15: 1750-7) provides some important information about where we are heading with regard to therapeutic drug monitoring (TDM) with vedolizumab (VDZ).

This study enrolled 47 consecutive patients with either Crohn’s disease (CD, n=31) or ulcerative colitis (UC, n=16). In those without a clinical response at week 6, an additional dose of 300 mg of VDZ was administered at week 10.

Key findings:

• VDZ levels were higher in responders than in nonresponders, which is in agreement with previous studies ( (NEJM 2013; 369: 711-21, NEJM 2013; 369: 699-710)
• A low therapeutic drug level as early as week 2 (<24.5 mcg/mL) and at the end of induction (week 6) (<18.5 mcg/mL) was associated with the need for drug optimization within 6 months in all patients
• All patients with a level <19.0 mcg/mL at week 6, regained a secondary response after optimization at week 10.
• The authors note that in the GEMINI trial, anti-VDZ antibodies were detected in 56 of 1434 patients (3.7%).  In this cohort, no anti-VDZ were detected using the same methods.

My take: Low trough levels of VDZ at week 6 are associated with the need for drug optimization/increased dosing.