A213 REDEFINING MILD-MODERATE ULCERATIVE COLITIS: PATIENTS WITH ENDOSCOPIC MAYO SCORE 1 AND ACTIVE HISTOLOGIC INFLAMMATION HAVE SIMILAR OUTCOMES TO PATIENTS WITH MAYO SCORE 2

Abstract Background Mild-to-moderate ulcerative colitis (UC) is conventionally defined as a total Mayo Clinic score of at least 4, with a Mayo Endoscopic Score (MES) of 2 and a Rectal Bleeding Score (RBS) of at least 1. Historically, endoscopic improvement with treatment has been defined as MES 0 or 1. However, studies have shown differences in prognosis between these two subsets of patients, with those who attain MES 1 reported to have higher rates of relapse. Patients with MES 1 and histologically active disease are currently excluded from contemporary clinical trials based on prevailing inclusion criteria. Consequently, insight into improving therapeutic outcomes for this patient population remains limited. Aims This study aims to explore whether UC patients with lower endoscopic burden but active histology have comparable outcomes to those with “conventional” mild-moderate UC. Methods This was a post-hoc analysis from the VARSITY study. Patients who completed induction (at week 14) with mild-moderate UC based on the conventional definition were compared to patients with histologically active MES 1 for achieving histo-endoscopic mucosal improvement (HEMI) at week 52, defined as Mayo endoscopic subscore ≤ 1 and Geboes highest grade < 3.2. Secondary outcomes included endoscopic remission (ER) (Mayo endoscopic subscore of 0), histologic improvement (Geboes highest grade < 3.2) and clinical remission (CR) (total Mayo score ≤ 2 and no subscore >1 on any of the four subcomponents). Histologically active disease was defined as Geboes highest grade > 3.2 (>50% of neutrophil crypt involvement in the epithelium). Results Week 52 outcomes were comparable among patients with mild-moderate UC compared to those with histologically active disease and MES of 1. At week 52, a similar proportion of patients achieved HEMI [19/79 (24.1%) vs. 28/113 (24.8%), p=0.908], ER [23/79 (29.1%) vs. 35/113 (31.0%), p=0.782], histologic improvement [23/79 (29.1%) vs. 36/113 (31.9%), p=0.685] and CR [38/79 (48.1%) vs. 66/113 (58.4%), p=0.158]. Conclusions Disease outcomes in patients with MES 1 and a Geboes score > 3.2 were comparable to those with conventional mild-to-moderate UC. These results highlight the need for clinical trialists to revisit and expand the current definition of mild-to-moderate UC. Further validation of these findings in other patient cohorts is recommended. Funding Agencies None