• Crohn’s disease
• Inflammatory bowel disease
• Pharmacokinetics
• Ulcerative colitis
• Vedolizumab

We read with interest the recent paper by Colombel et al 1 showing that vedolizumab is frequently used for patients with inflammatory bowel disease (IBD). There is evidence for an exposure–efficacy relationship for vedolizumab induction therapy.2 Increasing dosing frequency of vedolizumab to every 4 weeks leads to an improvement in clinical response in both ulcerative colitis (UC)3 and Crohn’s disease (CD).4 In contrast to anti-tumour necrosis factor (TNF) agents, the correlation between the response to dose optimisation and changes in the pharmacokinetic profile of vedolizumab-treated patients remains unknown. We performed a retrospective analysis of all vedolizumab-treated patients that increased dosing frequency because of primary non-response (≤week 14 after treatment initiation) or secondary loss of response (>week 14 after treatment initiation) in our tertiary referral IBD centre (Nancy University Hospital) between 1 April 2016 and 31 May 2017. Treatment response, defined as an improvement in clinical symptoms and objective signs of inflammation at the end of follow-up, was correlated with early changes from baseline of vedolizumab trough concentrations after dose optimisation.

Our cohort included 23 patients, of whom 7 (one UC, six CD) had primary non-response to vedolizumab and 16 (seven UC, nine CD) had secondary loss of response to vedolizumab. The median time since the start of vedolizumab was 6 months (IQR 3–9.5 months). The majority of patients (19/23) was anti-TNF experienced. After complete follow-up, with a median time of 9 months (IQR 5–13 months), the treatment response was restored in 12 out of 23 (52.2%) patients (4/8 UC, 8/15 CD). In three out of five patients, systemic steroid use at baseline could be stopped after dose optimisation. Vedolizumab trough levels at baseline were low in all patients regardless of treatment response. The mean change from baseline of vedolizumab trough levels at month 3 after dose optimisation was numerically higher in the group of responders versus the group of non-responders (table 1).

Early therapeutic drug monitoring after dose optimisation might improve timely detection of vedolizumab-treated patients with IBD in need for an altered treatment regimen, but more prospectively collected data are needed.