Mucosal eosinophil abundance in non-inflamed colonic tissue predict response to vedolizumab induction therapy in inflammatory bowel disease

Abstract Background Vedolizumab has shown efficacy, safety and tolerability as treatment for patients with inflammatory bowel disease (IBD). However, vedolizumab induction therapy only shows clinical response and remission in roughly 55% and 30% of IBD patients, respectively. Vedolizumab binds and blocks migration of T-lymphocytes and eosinophils. In this study, we aimed to explore the predictive value of mucosal eosinophils and serum eotaxin-1, an eosinophil chemoattractant, regarding response to vedolizumab induction therapy. Methods 84 IBD patients treated within the University Medical Center Groningen (UMCG) (37 Crohn’s disease [CD], 47 ulcerative colitis [UC]) were included. In a subset of 24 IBD patients (9 CD, 15 UC) histopathological data were analyzed for eosinophil counts in high power fields (hpf) in non-inflamed colon ascendens tissue prior to vedolizumab treatment. In another subset of 64 IBD patients, (28 CD, 36 UC) baseline serum eotaxin-1 was quantified prior to vedolizumab treatment. Clinical response or remission was defined as a decrease of the Harvey Bradshaw Index (HBI) for CD or Simple Clinical Colitis Activity Index (SCCAI) for UC together with physician’s global assessment (PGA). Serum eotaxin-1 was externally assessed as a biomarker for response to vedolizumab induction therapy in 100 IBD patients derived from the GEMINI 1 & 2 trials. Results Baseline eosinophil mucosal count was significantly higher in vedolizumab induction therapy responders, compared to primary non responders (69[34–138] vs. 24[18–28] eosinophils/hpf respectively, P<0.01). Baseline serum eotaxin-1 levels in the UMCG cohort were significantly elevated in therapy responders, compared to primary non-responders (0.33 vs. 0.20 ng/mL, P<0.01). The final prediction model based on mucosal eosinophil count showed an area under the curve (AUC) of 0.90 and serum eotaxin-1 an adjusted AUC of 0.79 The optimal with balanced cut-off value for eosinophil count was > 30 eosinophils/hpf with a sensitivity of 90.9% and specificity of 92.3% (Youden’s index 0.83). Results derived from the GEMINI I & II cohorts did not show any associations between eotaxin-1 levels and therapy response. Conclusion Mucosal eosinophil abundance in non-inflamed colon ascendens biopsies can predict vedolizumab induction therapy response in IBD patients. More studies are warranted to confirm these preliminary results and further investigate the additional value of eotaxin-1 regarding predicting vedolizumab therapy response.