Vertex Highlights Kidney Pipeline as Povetacicept Cuts Proteinuria 52% in Phase III

Key Points

• Povetacicept reduced proteinuria by 52% at 36 weeks in the Phase III RAINIER trial for IgA nephropathy, with consistent results across subgroups and a safety profile broadly similar to placebo. The FDA action date is Nov. 30.
• Vertex is positioning its kidney pipeline as a potentially $10 billion opportunity spanning four diseases: APOL1-mediated kidney disease, IgA nephropathy, membranous nephropathy and ADPKD.
• Inaxaplin’s Phase III AMPLITUDE trial is fully enrolled with 522 participants, and Vertex expects interim results early next year; potential accelerated approval will depend on one-year eGFR results rather than proteinuria alone.

Vertex Pharmaceuticals NASDAQ: VRTX outlined updates across its kidney disease pipeline at the American Society of Nephrology Kidney Week 2026, highlighting data for povetacicept in IgA nephropathy and inaxaplin in APOL1-mediated kidney disease, or AMKD.

Chief Executive Officer and President Reshma Kewalramani said the company has four renal diseases in mid- or late-stage development: AMKD, IgA nephropathy, membranous nephropathy and autosomal dominant polycystic kidney disease, or ADPKD. She said Vertex views the combined opportunity across those diseases as potentially comparable to a $10 billion franchise, though she characterized that as her view of the market opportunity.

Kewalramani said povetacicept, acquired through Vertex’s Alpine acquisition, is being developed for B-cell-driven diseases including IgA nephropathy, membranous nephropathy and myasthenia gravis. She added that the FDA action date for povetacicept in IgA nephropathy is Nov. 30.

Povetacicept Phase III Interim Results

Richard Lafayette, professor of medicine at Stanford University, reviewed interim results from RAINIER, a global Phase III randomized, double-blind, placebo-controlled study of povetacicept in adults with biopsy-proven IgA nephropathy.

Patients entered the study with urine protein-to-creatinine ratios above 0.75 grams per gram and estimated glomerular filtration rates above 30 mL/min. They were receiving maximally tolerated renin-angiotensin system inhibition, with stable use of other standard therapies, including SGLT2 inhibitors, mineralocorticoid receptor antagonists and, where available, endothelin blockers.

Participants were randomized two-to-one to receive povetacicept or placebo every four weeks. Lafayette said the interim analysis at 36 weeks showed a 52% reduction in proteinuria with povetacicept. He described the reduction as rapid, sustained and consistent across evaluated subgroups, including those defined by age, race, baseline proteinuria, kidney function, hematuria and SGLT2 inhibitor use.

The presentation also cited an approximately 80% reduction in galactose-deficient IgA1, a disease-related biomarker, at the end of the interim analysis period. More than 80% of treated patients with baseline hematuria had resolution by 20 weeks, according to Lafayette. Nearly half of patients reached a urine protein-to-creatinine ratio below 0.5 grams per gram, while nearly one in six achieved normal proteinuria by week 36.

Lafayette said the safety profile observed to date was similar to placebo, aside from generally mild injection-site reactions. There were no deaths reported during the interim period. He said povetacicept is administered as a once-monthly subcutaneous injection and is expected to be available in an auto-injector format in the open-label extension.

While Lafayette called the results “transformational efficacy,” he cautioned that comparisons with other BAFF/APRIL-targeting therapies remain premature. He said longer-term estimated glomerular filtration rate, or eGFR, results will be important for comparing kidney-function protection across treatments.

Inaxaplin and APOL1-Mediated Kidney Disease

Akinlolu Ojo, executive dean of the School of Medicine at the University of Kansas, discussed results from the AMPLIFIED study of inaxaplin in patients with AMKD who were not included in the Phase III AMPLITUDE trial.

AMPLIFIED included two cohorts: patients with low levels of proteinuria and patients with moderate proteinuria who also had diabetic kidney disease. Ojo said participants were already receiving contemporary background therapy for chronic kidney disease and, where applicable, diabetic nephropathy.

He said inaxaplin produced substantial and clinically meaningful reductions in urinary protein excretion in both cohorts. In the cohort with diabetic kidney disease, proteinuria reductions ranged from 17% to 25%. Ojo noted that confidence intervals crossed one in that cohort but argued the magnitude of reduction could still have longer-term clinical significance, citing historical results from the RENAAL trial of losartan in diabetic nephropathy.

Ojo said the larger Phase III AMPLITUDE study is fully enrolled, with 522 total participants, including 66 patients carried forward from a Phase IIb study and 456 newly enrolled Phase III participants. Vertex expects to share interim-analysis results early next year.

He said AMKD patients typically experience eGFR declines of roughly 5 to 8 mL/min per year, making a one-year kidney-function endpoint meaningful in this population. Kewalramani clarified that Vertex’s agreement with the FDA for potential accelerated approval of inaxaplin is based on one-year eGFR results, rather than proteinuria alone.

Commercial and Access Plans

Chief Commercial Officer Duncan McKechnie said Vertex has been engaging with commercial payers and pharmacy benefit managers regarding povetacicept since July 2025. He said about 70% of IgA nephropathy patients are commercially insured and that the company expects to provide more specific coverage updates during the first half of 2027.

McKechnie said Vertex expects some patients to receive treatment on a case-by-case basis before formal coverage arrangements are established and plans to offer a bridge program. He also said the company is not expecting payers to require step therapy through other APRIL/BAFF products.

Kewalramani said Vertex plans to discuss the future development path for inaxaplin in diabetic kidney disease with the FDA after AMPLITUDE results are available.

About Vertex Pharmaceuticals (NASDAQ:VRTX)

Vertex Pharmaceuticals Incorporated is a global biotechnology company focused on developing and commercializing medicines for serious diseases. Founded in 1989 and headquartered in Boston, Massachusetts, the company applies expertise in the science of human disease to discover therapies that address significant unmet medical needs.

Vertex is best known for its cystic fibrosis portfolio, which includes Kalydeco, Orkambi, Symdeko/Symkevi, and Trikafta/Kaftrio. These medicines target the underlying cause of cystic fibrosis for patients with specific mutations in the CFTR gene.

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