Peresolimab

AnaptysBio trumpeted a Phase 2b success in rheumatoid arthritis Wednesday morning after a similar program from Eli Lilly was discontinued late last year. Anaptys’ program, known as rosnilimab, hit its primary endpoint across all three dose levels. After 12 weeks, rosnilimab reduced patients’ average disease activity score compared to placebo. Disease activity was measured using C-reactive protein, which is produced by the liver in response to inflammation, across 28 different joints throughout the body. There was no apparent dose response across the three active arms. Anaptys enrolled 424 total patients and randomized them evenly among the drug and placebo cohorts. Rosnilimab is an antibody designed to target PD-1 expression on T cells, but in a manner different to the classical checkpoint inhibitors. The company says it can “deplete PD-1 high T cells and agonize the remaining PD-1+ T cells” in an effort to restore balance to the immune system in patients with inflammatory conditions. Lilly’s discontinued program peresolimab also attempted to agonize PD-1, and was an IgG1 antibody. Lilly announced the drug’s termination in rheumatoid arthritis during its third-quarter update last October, and full data from its Phase 2b trial are expected to be released at a medical conference sometime this year. The Lilly readout alarmed Anaptys investors, sending the latter’s stock price $ANAB down about 28% last October — its second-biggest single-day drop of the last 12 months. (The biggest came when an atopic dermatitis drug failed in December.) Anaptys’ data set off a roller coaster ride with its stock on Wednesday, rising as much as 35% premarket but then later sinking as much as 5% compared to Tuesday’s close. As of approximately 11 a.m. Eastern time, its stock price was up again by about 6%. In addition to rheumatoid arthritis, Anaptys is testing rosnilimab in ulcerative colitis, and moved up a Phase 2 trial readout to the fourth quarter of this year. Previously, the company had expected topline data in the first quarter of 2026. Anaptys’ trial’s secondary endpoints included a measure of how many patients scored “low” on disease activity scales, as well as the proportion of patients whose condition improved by 20%, 50% and 70%. In a note to investors last month, Leerink analyst David Risinger said Anaptys’ management set benchmarks for the secondary endpoints in two different patient populations: those who had been previously treated with antirheumatic drugs, and those who hadn’t. At week 14, Anaptys said Wednesday all of those benchmarks were surpassed and achieved statistical significance compared to the placebo group. The trial enrolled 250 treatment-naïve patients and 174 who had received prior treatment. However, the biotech did not break down week 12 data by patient subgroup, which was the time measurement used for the primary endpoint. Risinger said in a new note Wednesday morning the week 14 assessment may have introduced bias, as only patients who achieved “low” disease were allowed to continue treatment for up to six months. Across the entire trial population, secondary endpoint results were varied across dosing arms at 12 weeks , according to a press release, with some achieving statistical significance and others only reaching numerical superiority. There were also no major safety concerns.