Substudy 1 was a Phase 2b dose-ranging study designed to evaluate the efficacy and safety of different oral doses of upadacitinib compared to placebo as 8-week induction therapy in participants with moderately to severely active UC. Approximately 250 participants were planned to be randomized 1:1:1:1:1 to the placebo group and 4 upadacitinib doses (7.5, 15, 30, and 45 mg). Randomization was stratified by previous biologic therapy use (yes/no), Baseline corticosteroid use (yes/no), and Baseline Adapted Mayo score (≤ 7 or \> 7). The study duration included a Screening Period of up to 5 weeks and an 8-week double-blind (DB) Induction Period. After all randomized participants completed the 8-week induction, a dose-selection analysis of efficacy and safety (selected laboratory parameters) of upadacitinib versus placebo was performed. Based on this dose-selection analysis, one induction dose (upadacitinib 45 mg) was identified for further evaluation in two Phase 3 induction studies, M14-234 Substudy 2 and M14-675 (NCT03653026). During the analysis period, 132 additional participants were randomized into Groups 3 and 4 of Substudy 1 (upadacitinib 30 mg and 45 mg dose groups; approximately 66 participants per dose group). The objectives of enrolling these additional participants were to avoid interrupting the study activities during the analysis period and to support a sufficient number of participants with clinical response to be re-randomized into the maintenance portion in Substudy 3. Substudy 1 main participants are defined as those first 250 randomized 250, and additional participants are defined as those who were randomized after the main participants.

Substudy 2 was a two-part Phase 3 dose-confirming study designed to evaluate the efficacy and safety of oral administration of upadacitinib 45 mg compared to placebo as induction therapy for up to 16 weeks in participants with moderately to severely active UC. Substudy 2 included a Screening Period of up to 5 weeks, Part 1, and Part 2. Part 1 was a randomized, DB, placebo-controlled 8-week induction period. Part 2 was an open-label, 8-week extended treatment period for clinical non-responders from Part 1 of Substudy 2. Part 1 was planned to enroll 462 subjects; actual enrollment was 474 subjects. Eligible participants were randomized in a 2:1 ratio to one of the two treatment groups (DB upadacitinib 45 mg or matching placebo) for 8 weeks. The randomization was stratified by bio-IR status (Biologic inadequate responders \[bio-IR\] vs Non-biologic-inadequate responders \[non-bio-IR\], corticosteroid use (yes or no), and Adapted Mayo score (≤ 7 or \> 7) at Baseline. Within bio-IR, the randomization was further stratified by number of prior biologic treatments (≤ 1 or \> 1). Within non-bio-IR, the randomization was further stratified by previous biologic use (yes or no). Part 2 was an open label, 8-week Extended Treatment Period for those who did not achieve clinical response per Adapted Mayo score at Week 8 in Part 1. All participants received upadacitinib 45 mg.

Substudy 3 was a Phase 3 maintenance study designed to evaluate the efficacy and safety of upadacitinib 15 and 30 mg once daily (QD) compared to placebo in achieving clinical remission per Adapted Mayo score in participants with moderately to severely active UC who achieved clinical response per Adapted Mayo score following induction therapy from Substudy 1, Substudy 2, or Study M14-675. A total of 1,046 subjects who achieved clinical response per Adapted Mayo score after completion of induction treatment or Extended Treatment Period in Study M14-234 Substudy 1, Substudy 2, or Study M14-675 entered Substudy 3, and 1,044 were treated with a blinded treatment assignment for up to 52 weeks. Substudy 3 included 4 cohorts. Cohort 1: 847 participants who achieved clinical response in Substudy 1, Substudy 2, or Study M14-675 at either Week 8 or Week 16, and received upadacitinib 15, 30, or 45 mg QD. The treatment groups in Cohort 1 were Group 1: upadacitinib 15 mg QD; Group 2: upadacitinib 30 mg QD; and Group 3: placebo QD. Those who achieved clinical response and received upadacitinib 15 mg QD in Substudy 1 were re-randomized 1:1 to only receive upadacitinib 15 mg QD or placebo QD (treatment Group 1 or 3). Cohort 2: 104 participants who received double-blind placebo QD treatment for 8 weeks during Substudy 1, Substudy 2 Part 1, or Study M14-675 Part 1 and achieved clinical response at Week 8 continued to receive blinded placebo QD in Substudy 3. Cohort 3: 75 participants who received upadacitinib 45 mg QD in Induction Phase and did not achieve clinical response and received upadacitinib 45 mg QD in Extended Treatment in Substudy 2 Part 2 or in Study M14-675 Part 2 and achieved clinical response at Week 16 were re-randomized 1:1 and received blinded upadacitinib 30 mg QD or upadacitinib 15 mg QD in Substudy 3. Cohort 4: 20 participants who received double-blinded treatment of upadacitinib 7.5 mg QD for 8 weeks during Substudy 1 and achieved clinical response at Week 8 continued to receive blinded treatment of upadacitinib 7.5 mg QD in Substudy 3.