Efficacy & Safety of TD-1473 in Ulcerative Colitis

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