AnaptysBio has abandoned plans to develop rosnilimab for ulcerative colitis (UC) after the PD-1 agonist flunked a phase 2 study.
The San Diego-based biopharma assessed rosnilimab in the midstage study of 136 patients with moderate to severe UC across the U.S. and Europe. The study’s main goal was to demonstrate a mean change from baseline as measured by the modified Mayo Score (mMS) at Week 12, with key secondary endpoints evaluating clinical response and clinical remission.
Patients who received 400 mg of subcutaneous rosnilimab every four weeks or 800 mg every two weeks only achieved clinical remission rates of 7% , which was no better than the placebo cohort, Anaptys explained in a Nov. 10 release.
“While preliminary data suggest an increase in remission rates between week 12 and week 24, week 24 remission rates did not meet our six-month target product profile,” Anaptys added.
The results dent the high hopes for rosnilimab generated by a phase 2 win in rheumatoid arthritis (RA) in February. That success had offered some welcome clinical validation for Anaptys after the company had jettisoned an atopic dermatitis candidate three months early when the compound failed to reduce eczema area and itch severity in a phase 2b trial.
“Rosnilimab was safe and well tolerated, but we are disappointed in the lack of adequate efficacy and will discontinue the UC trial,” Anaptys CEO Daniel Faga said in this morning’s release.
The CEO attempted to focus investors' attention on ANB033, a CD122 antagonist already undergoing a phase 1b study for celiac disease. “We plan to announce a phase 1b in another inflammatory disease in 2026,” Faga pointed out.
Today’s decision to discontinue the UC trial for rosnilimab will save the company around $10 million, according to the release. Anaptys said it will provide an update on its plans for the PD-1 agonist in RA in the first half of next year, with this program needing to be funded by “strategic or other sources of capital without diluting our royalties.”
Next year, AnaptysBio plans to split into two publicly traded companies. One entity will take forward the biopharma’s clinical-stage pipeline, and the other will oversee its royalty-based agreements, headlined by Jemperli, the PD-1 blocking antibody that Anaptys discovered and has since brought GSK $2.7 billion in sales as an endometrial cancer and solid tumor drug.