A Study of Efficacy and Safety of Rosnilimab in Subjects With Moderate to Severe Ulcerative Colitis (ROSETTA)

Inclusion Criteria:

• Male or female ≥18

• Participants with a clinical diagnosis of UC for prior to Day 1

• Subject has moderate to severe, active UC, defined as a mMS ≥ 5 with an endoscopysubscore ≥2

• Subject has had a surveillance colonoscopy that did not detect potential dysplasiaor colon cancer performed within 1 year of Day 1.

• Subject has a history of an inadequate response, loss of response, or intolerance toany combination of at least 2 UC therapy classes defined as, but not limited to,aminosalicylates, corticosteroids, immunomodulators, calcineurin inhibitors, oradvanced UC therapies (e.g., biologics, JAK inhibitors, oral S1P receptormodulators, etc.)

Exclusion Criteria:

• Subject has a diagnosis of Crohn's disease or indeterminate colitis.

• Subject has a diagnosis of fulminant colitis and/or toxic megacolon.

• Subject has a history of an inadequate response, loss of response, or intolerance toany combination of 3 or more advanced UC therapy classes but not limited to, 1)anti-TNF antibodies (e.g., adalimumab, golimumab, infliximab), 2) other biologics (e.g., ustekinumab, vedolizumab), 3) oral JAK inhibitors (e.g., tofacitinib,upadacitinib), and 4) oral S1P receptor modulators (e.g., ozanimod).

• Subject has disease limited to the rectum (ulcerative proctitis)

• Subject has a history of colectomy (total or subtotal), ileoanal pouch, Kock pouch,or ileostomy or is planning bowel surgery.

• The subject had prior exposure to a PD-1 or PD-L1 agonist, antagonist, or modulator.