P280 Comparative responsiveness of disease activity indices in moderately-to-severely active Ulcerative Colitis: a post-hoc analysis of the UNIFI trial

Abstract Background Clinical, endoscopic, histological, and composite instruments are used to measure disease activity in ulcerative colitis (UC). We compared responsiveness of the Mayo Clinic Score (MCS), modified Mayo Clinic Score (mMS), partial Mayo Clinic Score (pMS), Robarts Histopathology Index (RHI), and UC-100 score after treatment with ustekinumab in patients with moderately-to-severely active UC. Methods Publicly available data from the phase 3 UNIFI induction trial (NCT02407236) comparing the efficacy and safety of ustekinumab versus placebo in patients with moderate-to-severe UC were obtained from Vivli (Vivli ID #7549) and Yale University Open Data Access Project (#2021-4848). Post-hoc analyses were performed on patient level data to ascertain outcomes of interest. Treatment assignment was the criterion for change in evaluation of responsiveness, which was quantified using the probability of a treated patient having a larger change than a placebo patient (win probability [WinP]) and estimated using nonparametric methods. Extent of responsiveness was interpreted according to Cohen’s benchmarks as very small (WinP<0.56); small (0.56≤ WinP<0.64); medium (0.64≤ WinP<0.71); and large (WinP≥0.71). Results Data from 961 patients with moderately-to-severely active UC randomised in UNIFI were included. At baseline, 319 patients received placebo and 624 patients received ustekinumab. A total of 912 (94.9%) patients completed the induction trial. Overall mean baseline index scores were: MCS 8.9 (±1.6), mMS 6.6 (±1.3), pMS 6.2 (±1.4), RHI 16.6 (±8.1), and UC-100 score 71.4 (±16.5) (Table). The UC-100 demonstrated a large degree of responsiveness (WinP 0.72 [95% CI: 0.66, 0.78]). The MCS (0.68 [0.62, 0.73]), mMS (0.69 [0.63, 0.75]), and pMS (0.65 [0.59, 0.71]) demonstrated similar, medium effect sizes (all comparisons p>0.05) (Figure). The RHI alone had a relatively small effect size (WinP 0.63 [0.56-0.70]). Among individual UC-100 components (Mayo Clinic stool frequency subscore, Mayo Clinic endoscopic subscore, and RHI), the endoscopic score was most responsive (WinP 0.59 [0.36-0.82]). The combination of endoscopy and RHI was associated with a medium degree of responsiveness (WinP 0.69 ([0.34, 1.00]). Conclusion UC disease activity indices are similarly responsive to change. Depending on trial design and measurement feasibility, different instruments can be considered optimal for evaluation of efficacy. The mMS is similarly responsive to the MCS without including the physician global assessment and may be more appropriate for determining trial eligibility and defining primary endpoint, whereas the UC-100 may be more appropriate for measuring treatment effect when an objective continuous measure is needed.

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