Kidney Week

Abstract: FR-PO0808

Safety, Tolerability, and Efficacy of Mezagitamab (TAK-079) as Add-On to Standard-of-Care Therapy in Individuals with Primary IgAN: Week 96 Data from an Open-Label Phase 1b Study

Session Information

• Glomerular Clinical Trials: From Data to Impact
  November 07, 2025 | Location: Exhibit Hall, Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Glomerular Diseases

• 1402 Glomerular Diseases: Clinical, Outcomes, and Therapeutics

Authors

• Barratt, Jonathan, Department of Cardiovascular Sciences, University of Leicester, Leicester, United Kingdom

Jonathan Barratt, MBChB, PhD

• Suzuki, Yusuke, Department of Nephrology, Juntendo University Faculty of Medicine, Tokyo, Japan

Yusuke Suzuki, MD, PhD

• Nguyen, Van Anh, Takeda Development Center Americas, Inc., Cambridge, Massachusetts, United States

Van Anh Nguyen, PhD

• Dobler, Iwona, Takeda Development Center Americas, Inc., Cambridge, Massachusetts, United States

Iwona Dobler, PhD

• Li, Cheryl, Takeda Development Center Americas, Inc., Cambridge, Massachusetts, United States

Cheryl Li, PhD

• Patwari, Parth, Takeda Development Center Americas, Inc., Cambridge, Massachusetts, United States

Parth Patwari, MD, ScD

• Farmer, Mk, Takeda Development Center Americas, Inc., Cambridge, Massachusetts, United States

Mk Farmer, MD

Background

There remains an unmet need for new therapies for immunoglobulin A nephropathy (IgAN) that can safely halt progression to kidney failure. Mezagitamab, a fully human anti-CD38 monoclonal antibody, depletes plasma cells, plasmablasts, and natural killer cells. Mezagitamab may allow stable kidney function over time by depleting cells that produce galactose-deficient IgA1, thus addressing the cause of the disease.

Methods

This open-label, single-arm, phase 1b, multicenter study (NCT05174221) evaluated mezagitamab as add-on to stable background therapy. Eligible participants had biopsy-proven disease and proteinuria with urine protein-to-creatinine ratio (UPCR) ≥1 g/g from a 24-hour urine collection or urine protein excretion ≥1 g/24 hours and estimated glomerular filtration rate (eGFR) ≥45 mL/min/1.73m². Participants received subcutaneous mezagitamab 600 mg once weekly for 8 weeks, then 600 mg every 2 weeks for 16 weeks (16 total doses). The primary endpoint was the percentage of participants with adverse events (AEs). Secondary and exploratory endpoints included serum IgA and IgG levels, percentage change from baseline in UPCR, and change from baseline in eGFR. Results are from a prespecified interim analysis.

Results

Seventeen participants enrolled (mean age 40.8 years, 53% female, 71% Asian). No serious AEs, discontinuations due to AEs, grade ≥3 infections, or opportunistic infections were reported. No new safety concerns were identified. Serum IgA and IgG were reduced with treatment (maximum mean reductions of 70% at Week 24 for IgA and 37% at Week 18 for IgG) and demonstrated varying levels of recovery by Week 96. At Week 96, UPCR was reduced by a model-based mean of 56.3% (95% CI: 30.2, 72.6; n=13). Renal function (eGFR) remained stable through Week 96 (mean change from baseline 2.9; 95% CI: −1.8, 7.6; n=12).

Conclusion

Mezagitamab was generally well-tolerated as an add-on to standard-of-care therapy and led to rapid and sustained reductions in UPCR and stable eGFR through Week 96.

Funding

• Commercial Support – Takeda Development Center Americas, Inc., Cambridge, MA, USA

Digital Object Identifier (DOI)

• doi: 10.1681/ASN.2025tvgzhny7