Relationship between vedolizumab serum concentrations in the induction phase and early and sustained response in the first year of treatment in patients with ulcerative colitis

Objective: Evidence on the usefulness of proactive monitoring of vedolizumab serum concentrations during the induction phase of treatment is limited. The objective of our study was to evaluate the effectiveness of measuring such concentrations during this phase in predicting response to treatment in patients with ulcerative colitis with a view to determining whether patients would benefit from early monitoring of vedolizumab serum concentrations. Method: This was a prospective descriptive study carried out at three public general hospitals. It included adult patients with ulcerative colitis who were initiated on vedolizumab at the participating hospitals from June 2019 to June 2020. Vedolizumab serum concentrations were determined at weeks 6 and 14. Response to treatment was biologically, clinically, and endoscopically evaluated at weeks 6, 14, and 52. An analysis was made of the relationship between vedolizumab serum concentrations at week 6 and early response to treatment, and of the relationship between the vedolizumab serum concentrations at weeks 6 and 14 and persistent response at one year. Results: A total of 45 patients were included of whom 22 (49%) were considered non-responsive after one year and required intensification of treatment. The median (interquartile range) vedolizumab serum concentrations obtained at 6 weeks was higher in patients who obtained an early response and in those who maintained the response at one year than in those who did not respond to vedolizumab [27.4 (19.0-40.8) mu g/ml vs 15.6 (13.4-28.5) mu g/ml; p = 0.018] and [29.9 (19.2-43.2) mu g/ml vs 18.2 (15.4-26.9) mu g/ml; p = 0.022] respectively. Vedolizumab serum concentrations >= 17.3 mu g/ml at week 6 were predictive of a good early response, and vedolizumab serum concentrations >= 26.1 mu g/ml at week 6 predicted a sustained response at one year. No relationship was found between vedolizumab serum concentrations at week 14 and a sustained response. Conclusions: We observed a relationship between vedolizumab serum concentrations determined at week 6, and early and maintained response to vedolizumab therapy in patients with ulcerative colitis, which supports early drug monitoring during the induction phase to individualize treatment and increase effectiveness.