Takeda Pharmaceutical Company announced promising interim data from a Phase 1b clinical trial demonstrating that mezagitamab (TAK-079), an experimental immunotherapy, maintains kidney function stability for extended periods even after treatment concludes. The results, reported by Drugs.com, presented at the American Society of Nephrology’s 2025 Kidney Week conference, offer hope for patients with immunoglobulin A (IgA) nephropathy, a rare and progressive kidney disease that currently lacks any curative treatment.
A Debilitating Disease with Limited Options
IgA nephropathy is a lifelong autoimmune kidney disorder typically diagnosed in young adults between ages 10 and 30. The disease causes progressive, irreversible kidney damage through abnormal immune complex deposits that trigger chronic inflammation. Approximately one in five patients progress to complete kidney failure within a decade of diagnosis, requiring dialysis or transplantation—a devastating prospect for patients often in their youth or early adulthood. Despite available treatments, therapeutic options remain limited, and no cure exists.
Revolutionary Mechanism of Action
Mezagitamab operates through a novel mechanism targeting the root cause of IgA nephropathy. The fully human monoclonal antibody depletes cells that express high levels of CD-38, including plasma cells, plasmablasts, and natural killer cells. These cells produce an abnormal protein called Gd-IgA1 that drives the disease process. By eliminating these pathogenic cells, mezagitamab theoretically interrupts immune complex formation, reduces kidney inflammation, and prevents progressive renal damage.
Compelling Clinical Evidence
The Phase 1b trial enrolled 17 patients with biopsy-proven IgA nephropathy who received subcutaneous mezagitamab injections (600 mg weekly for eight weeks, then biweekly for 16 weeks) as an addition to their existing therapies. Thirteen patients continued into extended follow-up observation.
The results proved remarkably encouraging. At Week 96—18 months after the final treatment dose—kidney function remained stable in 12 evaluable patients, with an average glomerular filtration rate (eGFR) change of +2.5 from baseline. Critically, this stability persisted despite completion of treatment, suggesting a disease-modifying rather than merely symptomatic effect.
Patients sustained a substantial 55.2% mean reduction in proteinuria (excess urinary protein), a key marker of kidney damage. Additionally, abnormal Gd-IgA1 levels were reduced by 50.1%, while immunoglobulin G levels completely recovered toward normal values. Most remarkably, 60% of patients achieved complete resolution of hematuria (blood in urine).
Exceptional Safety Profile
Mezagitamab demonstrated outstanding tolerability throughout the study. No serious adverse events occurred, including no serious hypersensitivity reactions, injection-site complications, opportunistic infections, or severe infections. This safety profile is particularly important given the immunosuppressive nature of CD-38 depletion therapy.
Rapid Clinical Development
Recognizing mezagitamab’s therapeutic potential, regulatory agencies have granted significant designations. The European Medicines Agency awarded Orphan Drug Designation in October 2025, while the U.S. FDA granted Breakthrough Therapy Designation in August 2025 for chronic immune thrombocytopenia. The drug is currently advancing through Phase 3 trials for both IgA nephropathy and immune thrombocytopenia, with patient enrollment underway.
Prof. Jonathan Barratt, the trial’s principal investigator, emphasized that sustained kidney function preservation after treatment completion represents a paradigm shift for this devastating disease, offering young patients affected by IgA nephropathy a potential opportunity to preserve their renal function long-term.
