Rosnilimab Demonstrates Best-in-Disease profile for Rheumatoid Arthritis in 6-Month Trial Data
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A new treatment option for rheumatoid arthritis (RA) is showing significant promise, with updated six-month data from the Phase 2b RENOIR trial demonstrating a “best-in-disease” profile for rosnilimab. The findings, released in June 2025, build upon earlier positive results and suggest a potential breakthrough in long-term disease management.
Novel Approach to RA Treatment
Rheumatoid arthritis is a chronic autoimmune disease that typically begins in adulthood, requiring lifelong management to prevent joint damage, organ complications, and diminished quality of life. According to a statement from a lead study investigator, Jonathan Graf, MD, professor of Medicine at the University of California, San Francisco, witnessing rosnilimab’s ability to dramatically reduce disease activity over six months – in both patients who have previously failed other treatments and those new to therapy – is “truly exciting” for the RA community.
Rosnilimab’s unique mechanism of action, targeting specific PD-1 expressing cells, appears to have a ample impact on the pathways driving RA, potentially restoring immune balance and achieving lasting remission. “Notable translational data provide further evidence…with the potential to restore immune homeostasis necessary to achieve meaningful, long-lasting disease remission,” the investigator added.
Significant Improvements Across Multiple Measures
Patients receiving rosnilimab experienced clinical and symptomatic improvements as early as three months into the trial. All three doses tested produced statistically significant reductions in DAS28-CRP and ACR20 scores at week 12 compared to placebo. During the placebo-controlled phase, both treatment-naive and treatment-experienced patients showed rapid ACR20 responses and reductions in C-reactive protein (CRP), mirroring results seen in trials of upadacitinib.
The efficacy of rosnilimab was comparable to that of JAK inhibitors, with responses deepening through six months in measures of CDAI low disease activity (LDA), CDAI remission, and ACR70, particularly in patients who had previously tried and failed other therapies at the 400mg Q4W and 600mg Q2W dosages. At the study’s outset, patients presented with high disease activity, with a mean CDAI of 38 and a median of 36.
In the overall study population of 318 patients, 45% achieved a CDAI score of ≤10 at week 12, increasing to 69% (220 patients) across all doses by week 14. This week 14 cutoff, required for continued participation in the all-active treatment period, created a ceiling on week 28 response rates. However, the study sponsor, Anaptys, noted that 12 patients who showed betterment after week 14 were initially counted as non-responders, but including them would have raised the week 28 CDAI LDA rate to 73% (232 of 318). Approximately 50% of patients who were ineligible for the all-active phase achieved ACR20 at week 14 and showed a trend toward CDAI LDA.
Durable Responses and Improved Patient Outcomes
Responses to rosnilimab proved durable, with CDAI LDA maintained for at least two months after treatment cessation. By week 34, 83% of patients who had achieved CDAI LDA remained in that state, while the remaining 17% were near the threshold, with a median CDAI of 13.
