FDA Approves Takeda's Mimrylo (Rusfertide) as First Hepcidin Mimetic for Polycythemia Vera

FDA Approves Takeda's Mimrylo (Rusfertide) as First Hepcidin Mimetic for Polycythemia Vera

On August 28, 2026, the U.S. Food and Drug Administration (FDA) approved Takeda and Protagonist Therapeutics' Mimrylo (rusfertide) for the treatment of erythrocytosis in adults with polycythemia vera (PV). Mimrylo is a first-in-class hepcidin mimetic peptide that regulates iron distribution and limits red blood cell overproduction, marking a potential paradigm shift in the treatment of this chronic blood cancer.

Maintaining a controlled hematocrit level below 45% is the primary clinical goal in PV to prevent life-threatening thrombotic events such as stroke, deep vein thrombosis, and pulmonary embolism. Historically, patients have relied heavily on therapeutic phlebotomy (bloodletting) to control hematocrit, which is burdensome and can cause systemic iron deficiency.

Phase 3 VERIFY Trial Efficacy and Safety

The FDA approval is supported by data from the global, randomized, double-blind, placebo-controlled Phase 3 VERIFY trial (NCT05210790), which evaluated weekly subcutaneously self-administered Mimrylo in 293 patients with PV who remained phlebotomy-dependent despite standard-of-care therapies (which could include hydroxyurea, interferon, and/or ruxolitinib).

• Primary Endpoint Met: The trial's primary endpoint was clinical response during Weeks 20–32, defined as the absence of eligibility for phlebotomy. A striking 76.9% of patients receiving Mimrylo achieved this clinical response, compared to 32.9% in the placebo group (P = 0.0001).
• Dramatic Reduction in Phlebotomy Burden: Only 27% of patients in the Mimrylo group required a therapeutic phlebotomy during the first 32 weeks of treatment, compared to 78% of patients in the placebo group. The mean number of phlebotomies per patient was reduced to 0.5 for the Mimrylo arm versus 1.8 for the placebo arm.
• Superior Hematocrit Control: A total of 62.6% of Mimrylo-treated patients maintained their hematocrit below 45% without phlebotomy, compared to just 14.4% of patients receiving placebo plus standard of care (P < 0.0001).
• Symptom and Fatigue Improvement: Mimrylo met all four key secondary endpoints, demonstrating a statistically significant improvement in fatigue as measured by the PROMIS Fatigue Short Form 8a.
• Tolerability Profile: Mimrylo was generally well-tolerated through 52 weeks of treatment, with the most common adverse reactions being injection-site reactions and mild anemia. Serious adverse events occurred in 3.4% of the Mimrylo group versus 4.8% of the placebo group, with none deemed treatment-related.

Market and Clinical Impact

Mimrylo was originally discovered and developed through Phase 3 by Protagonist Therapeutics before Takeda in-licensed the asset. By targeting the underlying mechanism of iron dysregulation, Mimrylo provides clinicians and patients with a highly effective, non-invasive alternative to repeated therapeutic phlebotomies¹, significantly reducing patient burden and improving overall quality of life.