Safety and Efficacy of Efavaleukin Alfa in Participants With Moderately to Severely Active Ulcerative Colitis

The main purpose of this study is to evaluate the effect of efavaleukin alfa on induction of clinical remission in participants with moderately to severely active ulcerative colitis (UC). Participants will be randomized to receive 1 of 3 efavaleukin alfa doses or placebo during a 12-week induction period. Participants who complete the 12-week induction period will have the option to enter an exploratory long-term treatment period for up to 40 weeks (total of up to 52 weeks of treatment) if, in the opinion of the investigator, they may benefit from continued treatment. During the long-term period, participants randomized to efavaleukin alfa will remain on the same efavaleukin alfa blinded dose; participants randomized to placebo who achieved clinical response at week 12 will remain on placebo; and placebo non-responders (ie, participants randomized to placebo who did not achieve clinical response at week 12) will receive efavaleukin alfa in a blinded manner during continued treatment. All participants will complete a safety follow-up visit 6 weeks after their last dose of investigational product.