Background: Vedolizumab (VDZ) has been found to be efficacious in the treatment of Crohn's disease (CD) and ulcerative colitis (UC), even though some patients present with non-response. The correlation between pharmacokinetics, immunogenicity and response to VDZ is not well understood and may play a role in clinical practice, particularly when optimizing therapy. The aim of this study was to assess correlation between VDZ trough levels and antibodies to VDZ (ATV) with rates of remission in patients with CD and UC.
Methods: This was a prospective cross-sectional study that included patients with CD or UC receiving maintenance treatment with VDZ. Variables included trough VDZ and ATV levels (measured using a validated drug-tolerant assay). Other variables collected during the study visit were C-reactive protein (CRP), Harvey Bradshaw index (HBI) in CD and Mayo Clinical Score (MCS) in UC. Mayo endoscopic score (MES) in UC and Simple endoscopic score-CD (SES-CD) in CD were also collected when endoscopy was performed. Primary outcome was deep remission (DR) defined as normal CRP and SES-CD≤2 (in CD) - MES≤1 (in UC) in addition to clinical remission (which was defined as an HBI<5 (in CD)/MCS<3 (in UC)). Secondary outcome was steroid-free remission (SFR) defined as DR while off steroids for 3 months.
Results: 56 patients were included (73% had CD). Twenty (36%) were on combination therapy with a thiopurine or methotrexate. Forty-three and 16% were in DR and SFR, respectively. Only 1 patient had ATV. VDZ levels were significantly higher in patients with DR and SFR when compared to those who did not achieve these outcomes (12.9 vs 9.4ug/mL [p=0.008] – Figure 1, and 15 vs. 9.5 [p=0.02] – Figure 2).
Patients with VDZ levels ≥5.1ug/mL (the first interquartile threshold) were more likely to be in DR (OR: 6.6 [95% CI: 1.55–45.8] p=0.009). A VDZ cutoff level of 5.1ug/mL best predicted DR (ρ: 0.713, p=0.03). Secondary outcome was steroid-free remission (SFR) defined as DR while off steroids for 3 months.
Conclusions: There is an association between VDZ drug levels and VDZ efficacy. These results suggest that there may be a role for therapeutic drug monitoring and drug optimization in patients receiving VDZ for CD or UC. Results from larger ongoing studies will be important.