P1014 Faecal loss of vedolizumab is associated with UC severity, lower serum vedolizumab levels and rates of clinical response – Results from the FAVOUR study

Abstract

Abstract Background Infliximab is detectable in the faeces of patients with active UC and faecal loss is associated with more severe disease and with primary non-response. Detection of vedolizumab (VED) in faeces and its importance in patients with UC has not been investigated. We conducted a prospective, observational study of patients with UC commencing VED to investigate faecal VED loss as well as its impact on serum VED levels (SVL) and association with treatment outcomes. Methods The FAVOUR study recruited UC patients with moderate to severe UC commencing vedolizumab between April 2019 and May 2022. Patients were treated with 300mg VED IV at weeks 0, 2, 6 and 14. Trough SVL were measured at weeks 2, 6 and 14. Faecal samples at days 1, 4, 7 and at weeks 2, 6 and 14 were homogenised and centrifuged to produce supernatants which were analysed for faecal VED levels (FVL) using a commercially available ELISA (LISA TRACKER, Theradiag, France). Clinical (SCCAI) and biochemical disease activity (CRP and faecal calprotectin) were measured at each infusion. Endoscopy was performed at baseline and week 14 to measure endoscopic (UCEIS/Mayo) and histologic activity (NHI). Correlations were calculated using the Spearman correlation coefficient (r). Categorical variables were compared using Mann-Whitney U. Results 36 patients (median age 34 (range 18-73); 13 Female) were recruited, of whom 33 completed induction therapy (3 withdrew early and were considered non-responders). 26/36 (72%) achieved a clinical response (SCCAI≤5 and reduction of ≥2) and 18/36 (50%) achieved endoscopic remission (UCEIS≤2). Faecal VED was detectable in 80/203 (39%) samples. Statistically significant correlations were observed between FVL and markers of clinical, biochemical, baseline endoscopic and histologic disease activity at day 1, and weeks 2 and 6 (table 1). Week 14 clinical non-responders had higher FVL than responders at that time point (median 1.0 vs 0.0ug/mL, p=0.004) but not at other timepoints. A statistically significant negative correlation was observed between week 2 FVL and SVL measured at weeks 6 and 14 (table 1). SVL did not differ significantly between week 14 responders and non-responders at any time point. Conclusion Active colonic inflammation results in faecal loss of vedolizumab. This appears to correlate with lower SVL and rates of response to treatment. However, SVL were not observed to directly influence rates of response. It is possible that FVL may be a marker of disease activity or that faecal loss results in lower rates of drug exposure at a tissue level and negatively impacts rates of response by this mechanism.