FDA Approves Rusfertide, the First-in-Class Hepcidin Mimetic for Polycythemia Vera
Polycythemia vera is a chronic myeloproliferative neoplasm characterized by abnormal overproduction of red blood cells, resulting in erythrocytosis (1,2). This excess red blood cell production increases hematocrit, the proportion of red blood cells relative to total blood volume, thereby increasing blood viscosity. In the United States, PV affects an estimated 90,000 individuals (2).
Elevated blood viscosity associated with uncontrolled hematocrit increases the risk of serious vascular complications, including stroke, deep vein thrombosis, and pulmonary embolism. Clinical data indicate that patients with PV and uncontrolled hematocrit levels have a four-fold higher risk of major cardiovascular events or cardiovascular death than those whose hematocrit is maintained within target limits. Beyond cardiovascular complications, PV is associated with a substantial symptom burden, including severe fatigue, pruritus (itching), night sweats, and impaired concentration (2).
Unmet needs in the management of Polycythemia Vera
A key objective in managing PV is maintaining hematocrit levels consistently below 45% to reduce thrombotic risk. Current standard-of-care approaches rely on therapeutic phlebotomy to reduce excess red blood cell mass, often in combination with cytoreductive therapies such as hydroxyurea, interferon, or ruxolitinib (1,2).
Despite available interventions, an estimated 78% of patients with PV continue to have uncontrolled hematocrit levels or remain dependent on frequent phlebotomy. Frequent phlebotomy can impose physical, logistical, and emotional burdens on patients while not directly addressing the underlying physiological drivers of erythrocytosis. Consequently, an unmet need remains for treatments that directly target iron regulation and red blood cell production (1,2).
FDA Approval of Rusfertide and Clinical Evidence
On August 28, 2026, the U.S. Food and Drug Administration (FDA) approved Rusfertide (Mimrylo), a first-in-class hepcidin mimetic, for the treatment of erythrocytosis in adults with polycythemia vera (PV) (1,2).
Rusfertide (Mimrylo) is a first-in-class, subcutaneously administered therapy discovered by Protagonist Therapeutics and developed through a global partnership with Takeda Pharmaceuticals. As a hepcidin mimetic, rusfertide regulates systemic iron distribution, restricting the availability of iron for erythropoiesis and thereby reducing excess red blood cell production. Rusfertide is administered once weekly by subcutaneous self-injection, starting at 19 mg and titrated individually to maintain hematocrit levels below 45% (1,2).
Following Priority Review designation, the FDA approved rusfertide for the treatment of erythrocytosis in adults with PV; the approval was granted to Takeda Pharmaceuticals America, Inc. Approval was based on data from the global, randomized, double-blind, placebo-controlled Phase 3 VERIFY trial (NCT05210790), which enrolled 293 adults with PV who remained dependent on phlebotomy despite ongoing standard-of-care treatment (1-3). Patients were randomized 1:1 to receive weekly subcutaneous rusfertide or placebo alongside standard-of-care therapy for 32 weeks (1). The primary efficacy endpoint was the proportion of patients who did not meet criteria for phlebotomy between Weeks 20 and 32 (1,2).
In this study, rusfertide demonstrated clear advantages over placebo. Significantly more patients achieved a clinical response (76.9% vs 32.9%, p<0.0001), with markedly fewer phlebotomy requirements (0.5 vs 1.8, p<0.0001) and better hematocrit control (62.6% vs 14.4%, p<0.0001). Patient reported outcomes also improved, showing reduced fatigue and symptom burden, while safety remained favorable with fewer serious adverse events and a lower incidence of new malignancies compared to placebo (4).
Clinical Benefits and Indication
Clinical results demonstrated that rusfertide maintained hematocrit control below 45% while reducing or eliminating the need for phlebotomy (1,2). Patients treated with rusfertide also demonstrated statistically significant improvements in fatigue, as measured by the PROMIS Fatigue Short Form 8a, along with reductions in total symptom burden assessed using the Myelofibrosis Symptom Assessment Form (MFSAF) Version 4.0 (2). Rusfertide is indicated for the treatment of erythrocytosis in adults with polycythemia vera (2).
Safety & Precautions
Rusfertide was generally well tolerated through 52 weeks of evaluation in clinical trials (2). The most common adverse reactions, reported in more than 15% of patients, were injection-site reactions (56%) and anaemia (16%) (2).
Rusfertide may increase platelet counts in patients with PV, with platelet elevations typically reaching a plateau by Week 8. Complete blood counts (CBCs) should be monitored every 2 to 4 weeks after treatment initiation and during dose modifications. Platelet elevations may require initiation or modification of cytoreductive therapy or adjustment or discontinuation of rusfertide (2).
Injection-Site Reactions: Localized reactions, including erythema, pruritus, pain, and swelling, can be managed with ice, topical corticosteroids, antihistamines, or analgesics (2).
Embryo-Fetal Toxicity: Animal reproduction studies indicate a potential risk of fetal harm. Pregnancy testing is recommended before treatment initiation in females of reproductive potential. Effective contraception is recommended during treatment and for at least 30 days after the final dose, and treatment should be discontinued if pregnancy occurs (2).
Lactation: Breastfeeding is not recommended during treatment and for 30 days after the final dose because of the potential for adverse effects in nursing infants, including impaired iron absorption (2).
Clinical Perspective
The FDA approval of rusfertide introduces a hepcidin-targeted approach for the management of erythrocytosis in adults with PV (1,2). By mimicking hepcidin and regulating iron homeostasis, rusfertide limits iron availability for erythropoiesis, supporting hematocrit control and reducing dependence on phlebotomy (1,2).
Healthcare providers should consult the full prescribing information for guidance on CBC monitoring, dose titration, and patient counselling (2).
About the Author
Dr. Manisha Dadlani is a Dental Surgeon and Medical Writer with 5+ years of clinical experience and formal training in medical writing. She combines clinical expertise with analytical thinking to develop evidence-based, insight-driven content that supports effective scientific communication across the healthcare and life sciences landscape.
References:
U.S. Food and Drug Administration (FDA). FDA approves first drug of its kind for polycythemia vera, a rare blood disorder. Available at: https://www.fda.gov/news-events/press-announcements/fda-approves-first-drug-its-kind-polycythemia-vera-rare-blood-disorder Accessed on 20 September, 2026.
Takeda Pharmaceutical Company Limited. FDA approves MIMRYLO (rusfertide) for polycythemia vera. Available at: https://www.takeda.com/newsroom/newsreleases/2026/fda-approval-mimrylo/ Accessed on 20 September, 2026.
ICH GCP. Rusfertide in Polycythemia Vera. Clinical Trials Registry: NCT05210790. Available at:https://ichgcp.net/clinical-trials-registry/NCT05210790 Accessed on 20 September, 2026.
Kuykendall A, Robinson K, et al. Rusfertide shows durable responses in Phase III VERIFY study of polycythemia vera. Presented at the 67th American Society of Hematology Annual Meeting and Exposition; January 2026. Published in ASH Clinical News. American Society of Hematology.
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