ROSETTA STUDY: This study will evaluate the safety, tolerability, and efficacy of Rosnilimab in subjects with moderate to severe ulcerative colitis (UC)

This is a Phase 2, randomized, double-blind, placebo-controlled, parallel-group, multicenter study to evaluate the efficacy, safety, tolerability, pharmacokinetics (PK), pharmacodynamics (PD), and immunogenicity of rosnilimab in subjects with moderate to severe ulcerative colitis (UC).

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 endoscopy subscore ≥2
• Subject has had a surveillance colonoscopy that did not detect potential dysplasia or colon cancer performed within 1 year of Day 1.
• Subject has a history of an inadequate response, loss of response, or intolerance to any combination of at least 2 UC therapy classes defined as, but not limited to, aminosalicylates, corticosteroids, immunomodulators, calcineurin inhibitors, or advanced UC therapies (e.g., biologics, JAK inhibitors, oral S1P receptor modulators, 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 to any 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.