Rosnilimab Demonstrates Sustained Clinical Benefits in Moderate-to-Severe Rheumatoid Arthritis: Phase 2b RENOIR Trial Extended Data Analysis

Deepening Response Rates Support Disease Modification Potential

The Phase 2b RENOIR trial has unveiled extended efficacy results for rosnilimab through Week 28 across a multinational cohort of 424 rheumatoid arthritis patients. Data presented at ACR Convergence 2025 indicate that clinical responses achieved at the Week 12 assessment continued to strengthen through Week 28, with particularly notable improvements in CDAI remission rates and ACR50/70 response metrics. This pattern of sustained benefit held consistently across patient populations regardless of prior biologic or targeted synthetic disease-modifying antirheumatic drug (b/tsDMARD) exposure, including those previously treated with TNF-alpha inhibitors, IL-6 receptor antagonists, or JAK inhibitors.

Among b/tsDMARD-experienced patients—representing 41% of the trial population—responses remained robust at mid and high rosnilimab doses (400mg monthly and 600mg biweekly), indicating therapeutic utility even in treatment-resistant populations. Notably, approximately 29% of experienced patients had prior JAK inhibitor exposure, a patient subset typically associated with more challenging disease management.

Durable Off-Drug Benefit Reshapes Treatment Timeline Expectations

The most striking finding involves the durability profile following treatment discontinuation. Upon completing Week 28 assessments, 220 of 318 rosnilimab-treated patients (71% of b/tsDMARD-naive and 66% of b/tsDMARD-experienced patients) who achieved CDAI low disease activity (LDA) thresholds entered a 10-12 week observation period off active drug. Clinical responses across multiple parameters—including CDAI LDA, mean CDAI scores, DAS28-CRP, and ACR50/70 rates—remained stable for the full three-month off-drug window through Week 38 trial completion. This sustained benefit without ongoing therapy represents a departure from conventional continuous-dosing paradigms in autoimmune disease management.

Mechanistic Validation Through Peripheral and Synovial T Cell Depletion

Translational biomarker data revealed the pathogenic T cell depleter mechanism achieved profound immunological effects. By Week 6, peripheral T follicular helper (Tph) cells were reduced by greater than 90% across all dose cohorts, with similar >90% reductions observed in synovial tissue at the mid and high-dose levels. Synovial biopsies demonstrated highly statistically significant reductions in both T cell and B cell activation markers (p<0.0001), with deeper suppression observed in CDAI LDA responders. These mechanistic findings support the hypothesis that selective pathogenic T cell elimination drives the observed clinical benefit while theoretically preserving protective immune function through sparing of naive T cell compartments.

Safety Profile Distinguishes Rosnilimab From Alternative Mechanism Classes

Through Week 38 follow-up, the cumulative safety database showed rosnilimab was well-tolerated with no treatment-related serious adverse events reported. The trial documented zero malignancies in rosnilimab-treated patients and no deaths across the population. This safety profile contrasts favorably with established comparator classes; notably, JAK inhibitors have generated regulatory safety advisories regarding malignancy risk and serious infections. The low dropout rate throughout the 38-week observation window further supports acceptable tolerability across the evaluated dose range.

Revised Efficacy Thresholds Achieved Across Primary and Higher-Order Endpoints

At Week 12, rosnilimab met the primary efficacy endpoint of DAS28-CRP superiority versus placebo across all tested doses, including the monthly 100mg dosing schedule. Secondary response measures including ACR20 criteria also demonstrated statistical and clinical significance. By Week 28, response rates intensified, with CDAI remission achievement rates and ACR50/70 responses showing continued improvement independent of prior therapy history. The evolution toward higher-order response thresholds—particularly CDAI remission rather than merely LDA—suggests potential for more complete disease control than standard-of-care therapies achieve.

Clinical Development Trajectory and Unmet Need Context

The RENOIR trial enrolled patients across North America and Europe, with 59% representing b/tsDMARD-naive populations and 41% b/tsDMARD-experienced. Participants received subcutaneous rosnilimab injections at 100mg, 400mg, or 600mg intervals, or placebo, while continuing background conventional disease-modifying antirheumatic drugs. The rosnilimab development pipeline extends beyond rheumatoid arthritis, with Phase 2 data expected from an ulcerative colitis trial in late 2025. The broader autoimmune disease portfolio includes ANB033 (CD122 antagonist) in celiac disease Phase 1b evaluation and ANB101 (BDCA2 modulator) in Phase 1a development.