AnaptysBio's investigational drug rosnilimab has demonstrated remarkable efficacy in treating moderate-to-severe rheumatoid arthritis (RA), achieving the highest-ever reported low disease activity responses in a Phase 2b clinical trial involving 424 patients.
Unprecedented Efficacy Results
The RENOIR trial met its primary endpoint, showing statistically significant improvements in DAS-28 CRP scores across all rosnilimab doses compared to placebo at Week 12. Most notably, 69% of rosnilimab-treated patients achieved Clinical Disease Activity Index (CDAI) low disease activity at Week 14, marking an unprecedented level of disease control.
The drug demonstrated strong performance across multiple efficacy measures, with significant improvements in ACR20, ACR50, and ACR70 responses. By Week 14, up to 82% of patients achieved ACR20 response, while 67% reached ACR50, and 48% attained ACR70 - substantially higher than placebo responses.
Novel Mechanism of Action
Rosnilimab's success stems from its innovative approach to targeting PD-1+ T cells. The drug achieved approximately 90% reduction in PD-1high T cells and 50% reduction in PD-1+ T cells, while increasing regulatory T cell populations. This resulted in favorable immune homeostasis and a clinically meaningful 50% reduction in C-reactive protein levels.
Safety and Tolerability Profile
The safety profile proved favorable through Week 12, with adverse event rates similar to placebo. Notable safety findings include:
- No reported malignancies or major adverse cardiovascular events
- No increased risk of serious infections compared to placebo
- Low incidence of injection site reactions
- No cases of anaphylaxis or systemic hypersensitivity
Broad Patient Benefit
The drug showed robust efficacy across both treatment-naive and experienced patients. In treatment-naive patients, Week 14 responses included:
- 75% achieving CDAI low disease activity
- 88% reaching ACR20
- 73% attaining ACR50
- 53% achieving ACR70
Market Impact and Future Directions
"These findings surpass our target product profile in the ~$20 billion U.S. RA market," stated Daniel Faga, CEO of AnaptysBio. The company plans to report complete six-month data and additional translational results in Q2 2025.
Dr. Jonathan Graf, professor at UCSF and RENOIR investigator, emphasized the significance of these results: "By depleting PD-1high expressing T cells and agonizing the remaining PD-1+ T cells, rosnilimab offers a fundamentally different approach to treating RA by resetting the immune system."
Trial Design and Patient Population
The Phase 2b RENOIR trial enrolled 424 patients with moderate-to-severe RA, including both biologic/targeted synthetic DMARD-naive (59%) and experienced (41%) patients. Participants received subcutaneous rosnilimab at doses of 100mg every four weeks, 400mg every four weeks, or 600mg every two weeks, compared against placebo.
The study population had a mean baseline DAS-28 CRP score of 5.64 and mean CDAI score of 37.7, indicating significant disease activity at enrollment. All patients continued their background conventional disease-modifying antirheumatic drugs throughout the trial.
