Efficacy & Safety of TD-1473 in Ulcerative Colitis

This protocol consists of 3 separate studies: an 8-week Phase 2b dose-finding induction
study, an 8-week dose-confirming Phase 3 induction study, and a 44-week Phase 3 maintenance
study. Subjects who respond to induction will enter the maintenance study; those who do not
will receive TD-1473 during extended induction. The safety and efficacy data of the Phase 2b
study will be analyzed to select the induction and maintenance dose regimens for the
confirmatory Phase 3 studies. Participants who have disease relapse or complete the
maintenance study may be eligible to enter a separate long-term safety study. Efficacy,
pharmacokinetic, biomarkers, and safety will be evaluated in all 3 studies.

240 subjects are planned for the Phase 2b and 640 subjects are planned for the Phase 3.

Inclusion Criteria:

- Is at least 18 years of age at screening

- Has a history of UC for at least 3 months prior to screening

- Has moderately-to-severely active UC, as defined by a Mayo endoscopic subscore of ≥2
points and an adapted Mayo score between 4 - 9 points inclusive

- Is corticosteroid-dependent or has demonstrated inadequate response, or intolerance to
conventional therapy (aminosalicylates, corticosteroids, immunomodulators) or
biologics

- Willing to use highly-effective methods of contraception during the study and for 7
days after the last dose

- Additional inclusion criteria apply

Exclusion Criteria:

- Has symptoms suggestive of fulminant colitis, megacolon or intestinal perforation

- Likely to require surgery for UC or other major surgeries

- Has previously received / is currently receiving prohibited medications within
specified timeframe

- Is refractory to 3 biologics with ≥2 mechanisms of action

- Has a current bacterial, parasitic, fungal, or viral infection

- Has clinically significant abnormalities in laboratory evaluations

- Has had any prior exposure to an approved Janus kinase (JAK) inhibitor or potential
exposure to an investigational JAK inhibitor that was stopped due to intolerance or
lack of efficacy

- Additional exclusion criteria apply