A composite disease activity index for early drug development in ulcerative colitis: development and validation of the UC-100 score

BACKGROUND: Combining clinical, endoscopic, and histological data associated with ulcerative colitis disease activity in a composite index could be a more sensitive way to detect efficacy in small numbers of patients during early drug development. Our aim was to derive and externally validate a novel index for this purpose. METHODS: Index development was done with data from a phase 2 placebo-controlled trial of ozanimod in patients with moderate-to-severe ulcerative colitis (n=179). Multivariable logistic regression modelling determined associations between candidate index items and absence of rectal bleeding (Mayo Clinic rectal bleeding subscore of 0), with items with a p value of less than 0·10 being taken forward into the final model. Model fit was internally validated and then externally validated in an independent phase 2 clinical trial dataset (MLN02, n=146) by measuring the area under the curve of the receiver operating characteristic (AUROC). FINDINGS: In the derivation cohort, multivariable analysis indicated that the Mayo Clinic stool frequency subscore (odds ratio [OR] 0·43, 95% CI 0·30-0·61; p