AnaptysBio Halts Rosnilimab Development for Ulcerative Colitis, Shifts Focus to Other Programs

AnaptysBio, a San Diego-based biopharmaceutical company, has announced the discontinuation of its rosnilimab development program for ulcerative colitis (UC) following disappointing results from a phase 2 clinical trial. The company is now redirecting its efforts towards other pipeline candidates and strategic initiatives.

Phase 2 Trial Failure and Program Discontinuation

The phase 2 study, which enrolled 136 patients with moderate-to-severe UC across the United States and Europe, failed to meet its primary endpoint. The trial evaluated two dosing regimens of rosnilimab, a PD-1 agonist: 400 mg administered subcutaneously every four weeks and 800 mg every two weeks.

Results showed clinical remission rates of 5% and 4% for the respective dosing groups, falling short of the 7% rate observed in the placebo cohort. While preliminary data suggested an increase in remission rates between week 12 and week 24, the company stated that "week 24 remission rates did not meet our six-month target product profile."

Daniel Faga, CEO of AnaptysBio, commented on the outcome: "Rosnilimab was safe and well tolerated, but we are disappointed in the lack of adequate efficacy and will discontinue the UC trial."

Strategic Shift and Financial Implications

The decision to halt the UC trial for rosnilimab is expected to result in cost savings of approximately $10 million for AnaptysBio. The company plans to provide an update on its strategy for rosnilimab in rheumatoid arthritis (RA) in the first half of 2026, emphasizing that any further development in this indication would require funding from "strategic or other sources of capital without diluting our royalties."

AnaptysBio is now focusing investor attention on ANB033, a CD122 antagonist currently in a phase 1b study for celiac disease. Faga announced plans to initiate a phase 1b trial for ANB033 in another inflammatory disease in 2026.

Corporate Restructuring and Future Plans

Looking ahead to 2026, AnaptysBio intends to split into two publicly traded companies. One entity will focus on advancing the company's clinical-stage pipeline, while the other will manage royalty-based agreements. This includes overseeing Jemperli, a PD-1 blocking antibody discovered by AnaptysBio and now marketed by GSK for endometrial cancer and solid tumors, which has generated $2.7 billion in sales.

The company's strategic decisions reflect a broader trend in the pharmaceutical industry, where firms are increasingly willing to quickly pivot away from underperforming programs and restructure to maximize value from successful assets and promising pipeline candidates.