Abstract Background The safety and efficacy of mirikizumab (miri), an anti-IL-23p19 antibody, for moderately-to-severely active ulcerative colitis (UC) have been shown in Phase 3 trials (LUCENT-1 and -2; NCT03518086, NCT03524092).1 Extended induction with 3 additional intravenous (IV) doses of miri induced clinical response at Week (W)24 in more than 50% of patients who did not initially achieve clinical response to induction with miri at W12.2 Among the clinical non-responders, some had achieved partial response at W12 (Table 1). We assessed response over time in clinical non-responders at the end of induction who received extended induction with miri for an additional 12W. Methods In LUCENT-1, patients (N=1281) were randomly assigned 3:1 to receive miri 300mg or placebo IV at W0, W4, and W8. Patients not achieving clinical response with miri 300mg IV at W12 of LUCENT-1 (n=272) received extended induction treatment with open-label miri 300mg IV at W12, W16, and W20 (LUCENT-2). Symptomatic remission, symptomatic response, bowel urgency (BU) remission, and BU change from baseline at W16 and W20 are reported (definitions in Table 1) in addition to the previously disclosed outcomes at W24. For categorical variables, number and percentage of patients who are responders/remitters were presented. For continuous variables, mean change from baseline with standard deviation (SD) was used. Missing data were imputed as non-response. Results Among patients who were clinical non-responders to 12W of initial induction treatment (n=272), 53 (19.5%); 73 (26.8%); 101 (37.1%) achieved symptomatic remission and 144 (52.9%); 169 (62.1%); 197 (72.4%) patients achieved symptomatic response at W16, W20, and W24, respectively. Among miri induction non-responders with Urgency Numeric Rating Scale (NRS) score ≥3 at induction baseline (n=256), 10.9% achieved BU remission at W16, 14.8% at W20, and 19.9% at W24. There was a 1.8±2.4 (mean±SD) point reduction in Urgency NRS scores at W16, 2.1±2.5 reduction at W20, and 2.5±2.7 reduction at W24 (Table 1). Conclusion Among patients who were clinical non-responders to induction at W12, more than 50% achieved clinical response after 3 additional induction doses with miri. A proportion of patients benefited earlier from extended induction at W16 and W20, respectively, regarding symptomatic response and remission, and BU outcomes. The results demonstrate continued symptomatic improvement and further support the potential benefit of extended induction treatment.
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