OSAKA, JAPAN & CAMBRIDGE, MASS. -- Takeda (TSE:4502/NYSE:TAK) announced new interim data from the Phase 1b, open-label, proof-of-concept study of subcutaneous mezagitamab (TAK-079), an anti-CD38 monoclonal antibody with disease-modifying potential, in primary immunoglobulin A (IgA) nephropathy. Data from the study showed that kidney function (eGFR) remained stable in patients with IgA nephropathy through Week 96 - up to 18 months after the last mezagitamab dose.[1] The results were presented at the American Society of Nephrology (ASN) Kidney Week 2025 in Houston.

IgA nephropathy is a lifelong progressive autoimmune disease often diagnosed in young people aged 10-30 years old that causes irreversible damage to the kidney function.[2] It has no cure, and despite available treatments, approximately one in five patients experience renal failure within 10 years of diagnosis.[3] By depleting cells that produce an abnormal protein called Gd-IgA1 implicated in the pathogenesis, mezagitamab targets early steps in the process leading to disease in IgA nephropathy.

“Mezagitamab targeted the underlying immune mechanisms of IgA nephropathy, with data showing that kidney function remained stable in patients after the last dose of treatment,” said Prof. Jonathan Barratt, M.D., Ph.D., principal investigator for the Phase 1b study and the presenting author. “This is especially critical given the progressive and often silent nature of the disease, with many patients already experiencing some degree of kidney damage by the time they’re diagnosed. Without effective intervention, the risk of renal failure - and the need for dialysis or transplant - remains alarmingly high.”

In the study, 17 patients with IgA nephropathy were treated with mezagitamab as an add-on to stable background therapy, and 13 patients continued into the long-term follow-up period. At Week 96 - 18 months after the last dose - kidney function remained stable (mean change in eGFR from baseline +2.5; 95% CI: −1.8, +7.6; n=12) and patients sustained a 55.2% (95% CI: 30.2, 72.6; n=13) mean reduction in proteinuria (protein in the urine) measured using a urine protein-creatinine ratio (UPCR).[1] Sustained reductions of 50.1% in Gd-IgA1 and complete recovery toward baseline in IgG were observed by Week 96.1 Hematuria (blood in the urine) was resolved in 60% of patients by Week 96.[1]

In this study, mezagitamab was generally well tolerated with no new safety concerns identified. No serious adverse events (AEs), including no serious hypersensitivity or injection-related reactions, discontinuations due to AEs, opportunistic infections or grade ≥3 infections were reported.[1]

“These promising data reinforce our belief in the potential of mezagitamab to redefine how autoimmune diseases like IgA nephropathy are treated - by targeting their root cause,” said Obi Umeh, M.D., M.Sc., Vice President, Franchise Global Program Leader at Takeda. “With patient enrollment ongoing in our Phase 3 trials investigating mezagitamab in IgA nephropathy and immune thrombocytopenia, we are excited to advance these promising programs and remain committed to bringing innovative solutions to patients with high unmet need.”

Mezagitamab is currently in Phase 3 clinical development for the treatment of both primary IgA nephropathy (NCT06963827) and chronic immune thrombocytopenia (NCT06722235) with the first patients now enrolled. In October 2025, mezagitamab was granted Orphan Drug Designation by the European Medicines Agency for the treatment of primary IgA nephropathy. In August 2025, mezagitamab was granted Breakthrough Therapy Designation by the U.S. Food and Drug Administration for the treatment of adult patients with chronic immune thrombocytopenia who have had an insufficient response to previous treatment. Takeda is assessing additional indications for mezagitamab.