Longer dosing period with mirikizumab for UC may induce response in initial nonresponders

Administering extended doses of mirikizumab for an additional 12 weeks successfully produces a clinical response in up to 50 percent of ulcerative colitis (UC) patients who did not benefit from 12 weeks of induction doses, according to the results of a phase II trial.

This study was a continuation of I6T-MC-AMAC, in which patients with moderate-to-severe UC were randomized to undergo 12 weeks induction therapy with 50-, 200-, or 600-mg mirikizumab or placebo.

At week 12, patients showing no clinical response (defined as a 9-point decrease in Mayo subscore of ≥2 points and ≥35-percent from baseline, and either a decrease of rectal bleeding subscore of ≥1 or a rectal bleeding subscore of 0 or 1) were offered the opportunity participate in an open-label, extended induction study for another 12 weeks. In this phase, the patients were given intravenous mirikizumab at either 600 mg (n=20) or 1,000 mg (n=64) every 4 weeks. At week 24, patients with a clinical response continued treatment and received 200-mg subcutaneous mirikizumab.

Among nonresponders to induction mirikizumab, 50.0 percent of those who received the 12-week extension of 600 mg mirikizumab and 43.8 percent of those who received the 1,000-mg dose achieved a clinical response, with 15.0 percent and 9.4 percent showing clinical remission, respectively. Endoscopic improvement occurred in 20.0 percent of patients in the 600-mg group and 15.6 percent in the 1,000-mg group.

At the end of the maintenance phase at week 52, 65.8 percent of patients sustained the clinical response, 26.3 percent achieved clinical remission, and 34.2 percent had endoscopic improvement.

There were no new safety concerns detected.