Vertex reports positive Week 36 interim results from the Phase 3 RAINIER trial showing povetacicept significantly reduced proteinuria and met all key endpoints in adults with IgA nephropathy.
Written By: Sana Khan BPharm
Reviewed By: Pharmacally Editorial Team
Vertex Pharmaceuticals has reported positive results from a pre-specified Week 36 interim analysis of the Phase 3 RAINIER trial evaluating povetacicept in adults with immunoglobulin A nephropathy (IgAN), meeting both the primary endpoint and all secondary endpoints.
Reduction in Proteinuria Achieves Primary Endpoint
In the interim analysis population, treatment with povetacicept resulted in a 52.0% reduction from baseline in 24-hour urine protein-to-creatinine ratio (UPCR) at Week 36. Compared with placebo, the therapy achieved a statistically significant 49.8% reduction in proteinuria (P<0.0001), demonstrating a clinically meaningful improvement. The reduction in proteinuria was consistent across all pre-specified patient subgroups.
Secondary Endpoints Also Met with Significant Improvements
The trial also met both alpha-controlled secondary endpoints. Povetacicept treatment led to a 77.4% reduction in serum galactose-deficient IgA1 (Gd-IgA1) from baseline, compared with a 9.1% increase in the placebo group, resulting in a 79.3% reduction versus placebo (P<0.0001).
Additionally, 85.1% of patients receiving povetacicept achieved hematuria resolution, compared with 23.4% in the placebo group, translating to a 61.7% improvement over placebo (P<0.0001).
Safety Profile Remains Favorable
Povetacicept was generally safe and well tolerated, with most adverse events classified as mild to moderate. No serious adverse events related to the drug and no deaths were reported.
Common adverse events included upper respiratory tract infection, nasopharyngitis, and injection site reactions, while serious adverse events occurred in 3.0% of patients in the povetacicept group compared with 4.3% in the placebo group.
RAINIER Trial Design
RAINIER (NCT06564142) is a global, randomized, double-blind, placebo-controlled Phase 3 trial evaluating povetacicept 80 mg administered subcutaneously every four weeks on top of standard of care.
A total of 605 patients were randomized, with 557 patients included in the main cohort and 199 patients forming the interim analysis population. Most participants were receiving background therapies such as ACE inhibitors or ARBs (97.8%) and SGLT2 inhibitors (67.7%), reflecting real-world treatment settings.
Regulatory Plans and Next Steps
Vertex has already begun submitting modules for a Biologics License Application (BLA) to the U.S. Food and Drug Administration, which granted rolling review for povetacicept in IgAN. The company expects to complete the BLA submission by the end of March, seeking accelerated approval.
If approved, Vertex plans to launch the therapy using a low-volume subcutaneous auto-injector administered once every four weeks at home. The RAINIER trial will continue blinded, with final results expected after two years of treatment (Week 104) focusing on changes in estimated glomerular filtration rate (eGFR).
Mechanism and Disease Background
Povetacicept is an engineered fusion protein that dual-inhibits BAFF and APRIL cytokines, key drivers of B-cell activation and survival involved in autoimmune diseases. By blocking these pathways, the therapy aims to control the immune mechanisms underlying IgA nephropathy. Povetacicept has received FDA Breakthrough Therapy Designation for the treatment of IgA nephropathy (IgAN).
IgA nephropathy is the most common form of primary glomerulonephritis, affecting about 330,000 people in the United States and Europe and more than 1.5 million globally. The disease is driven by immune complex deposition in the kidneys and can lead to progressive kidney damage, with up to 72% of patients progressing to end-stage renal disease or death within 20 years of diagnosis.
Reference
Vertex Announces Positive Week 36 Interim Analysis Results for Primary and All Secondary Endpoints in the RAINIER Phase 3 Trial of Povetacicept in Adults with IgA Nephropathy, Mar 9, 2026. 71a23b8d-761d-4ee3-a7d7-990e21df090c
Evaluation of Efficacy of Povetacicept in Adults with Immunoglobulin A Nephropathy (IgAN), ClinicalTrials.gov ID NCT06564142. https://clinicaltrials.gov/study/NCT06564142
About the Writer
Sana Jamil Khan is a B.Pharm graduate with a strong interest in medical writing and scientific communication. Her work focuses on interpreting clinical research, exploring developments in pharmaceutical science, and presenting complex medical information in a clear and accessible manner. She is particularly interested in topics related to human clinical studies, drug safety observations, and emerging therapeutic research.