On June 3, AnaptysBio Inc. (NASDAQ:ANAB) announced that its investigational drug, rosnilimab, demonstrated a best-in-disease profile in a robust and global 424-patient Phase 2b trial for moderate-to-severe rheumatoid arthritis/RA. Rosnilimab, which is a PD-1+ T cell depleter and agonist, achieved JAK-like efficacy over 6 months on key measures such as low disease activity/LDA and remission on the Clinical Disease Activity Index/CDAI, as well as ACR70 response.

A scientist in a biotechnology laboratory studying a new therapeutic product candidate.
Responses proved durable for at least 2 months off-drug, which suggested potential for extended maintenance dosing (for instance, Q8W). The drug was safe and well-tolerated, with most patients showing improvement by 3 months. All 3 doses (100mg Q4W, 400mg Q4W, 600mg Q2W) achieved statistically significant reductions in DAS-28 CRP and ACR20 at Week 12 versus placebo. CDAI LDA (≤10) was achieved by 45% of 318 rosnilimab patients by Week 12, increasing to 69% (220 responders) across all doses by Week 14.
As of the March 11 data cutoff, 83% of CDAI LDA responders at Week 28 were still in LDA at Week 34. Patient-reported outcomes, including pain and function, also showed clinically meaningful improvements. Translational data revealed deep reductions of ~90% in PD-1high T cells and ~50% in PD-1+ T cells in blood and synovial biopsies, indicative of robust on-target activity. Rosnilimab exhibited a favorable safety profile with no treatment-related serious adverse events, malignancies, or anaphylaxis, and a low discontinuation rate of less than 2%. The company aims to complete its Phase 2 study for rosnilimab in ulcerative colitis/UC with initial data expected in Q4 2025.
AnaptysBio Inc. is a clinical-stage biotechnology company that delivers immunology therapeutics. The company was formerly known as Anaptys Biosciences and changed its name to AnaptysBio in July 2006.
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This article is originally published at Insider Monkey.





