Anaptys discontinues ulcerative colitis trial after rosnilimab fails endpoints

AnaptysBio Inc. (NASDAQ: ANAB) announced that its Phase 2 trial of rosnilimab in moderate-to-severe ulcerative colitis failed to meet primary and secondary endpoints at week 12. The company will discontinue the trial, resulting in at least $10 million in savings.

The randomized, double-blind, placebo-controlled study enrolled 136 patients across the U.S., Western and Eastern Europe with a baseline mean modified Mayo Score of 6.7. Patients received either 400mg subcutaneous rosnilimab every four weeks, 800mg every two weeks, or placebo.

Clinical remission was achieved by 7% of patients receiving either rosnilimab dose compared to placebo rates within expected historical ranges. Endoscopic remission was achieved by 5% and 4% of patients receiving the respective doses. The drug showed approximately 90% depletion of pathogenic T cells but lacked adequate efficacy.

"Rosnilimab was safe and well tolerated, but we are disappointed in the lack of adequate efficacy and will discontinue the UC trial," said Daniel Faga, president and chief executive officer.

The drug demonstrated a favorable safety profile with no treatment-related serious adverse events, malignancies, or serious infections. Most adverse events were mild to moderate, with nasopharyngitis, ulcerative colitis, dizziness and injection site erythema occurring in more than 5% of participants.

Anaptys plans to provide an update on rosnilimab advancement in rheumatoid arthritis in the first half of 2026, funded by strategic or other capital sources. The company anticipates ending 2025 with approximately $300 million, including an expected $75 million milestone from GSK once Jemperli achieves $1 billion in global net sales.

The company reaffirmed its intention to separate biopharma operations from royalty assets in 2026.

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