Mimrylo (rusfertide)
An approved treatment for Polycythemia Vera.
The same compound appears under different names depending on the context. Here is how to identify Rusfertide wherever you encounter it, plus the key facts at a glance.
- Generic name
- Rusfertide
- Brand name
- Mimrylo
- Development code
- PTG-300
- Drug class
- Hepcidin mimetic
- Manufacturer
- Takeda (discovered by Protagonist Therapeutics)
- How it's taken
- Mimrylo is injected under the skin of the abdomen, the front of the thigh or the outer upper arm (upper arm only when a caregiver gives it) once a week, by the patient or a caregiver after training from the care team.
A once-weekly injection under the skin, approved by the FDA on August 28, 2026 to treat erythrocytosis (too many red blood cells) in adults with polycythemia vera. The FDA described it as the first approved polycythemia vera treatment that mimics hepcidin, a hormone that regulates iron. In its main trial, 76.9% of patients no longer qualified for a phlebotomy during weeks 20 to 32, against 32.9% on placebo.
Where Rusfertide fits
The first hepcidin mimetic approved for polycythemia vera, according to the FDA. It lowers red cell production by limiting iron and was studied on top of phlebotomy and drugs such as hydroxyurea, interferon and ruxolitinib, not as a replacement for them.
How Rusfertide works
Making red blood cells takes iron. Hepcidin is a natural hormone that regulates iron in the body. Rusfertide mimics hepcidin and blocks ferroportin, the body's iron transporter, which reduces the iron available for making red blood cells and lowers hematocrit, the share of the blood made up of red cells[1][3]. Because iron stays in storage instead of being used, ferritin (a measure of stored iron) rose on average from 21 to 124 mcg/L by week 32 in the main trial[1]. In that trial it was added to each patient's usual care, which could include phlebotomy, hydroxyurea, interferon or ruxolitinib[1].
Mechanism: Injectable peptide that mimics hepcidin, the body's iron-regulating hormone, blocking the iron exporter ferroportin to limit the iron available for making red blood cells
Side effects and safety
- New or worsening high platelet counts (thrombocytosis). Platelets rose an average of 31% within 4 weeks and leveled off by week 8. Blood counts every 2 to 4 weeks after starting and during dose changes; other treatment may need to be started or adjusted.
- Injection site reactions. In 56% of patients vs 33% on placebo, mostly mild. Ice, steroid creams, antihistamines or pain relievers can help.
- Harm to an unborn baby. Pregnancy test before starting, and effective contraception during treatment and for at least 30 days after the last dose. Stop Mimrylo if pregnancy occurs.
- Complete blood count every 2 to 4 weeks after starting and during dose changes
- Pregnancy test before starting in women who could become pregnant
- No breastfeeding during treatment and for 30 days after the last dose
Mimrylo has no boxed warning and no contraindications. In the 32-week placebo-controlled part of the VERIFY trial, side effects more common than on placebo were injection site reactions (56% vs 33%), anemia (16% vs 4.1%), high platelet counts (8% vs 0.7%) and shortness of breath (8% vs 1.4%). Injection site reactions were mostly mild redness, itching, pain or swelling. Platelet counts rose an average of 31% within 4 weeks of starting, went above 600,000 per microliter in 36% of patients and above 1,000,000 in 6%, and generally leveled off by week 8, so blood counts are checked every 2 to 4 weeks after starting and after dose changes. Anemia led to dose reductions in 10% of patients. Based on animal studies, it may harm an unborn baby[1].
This is not a complete list of side effects. Talk to your doctor or pharmacist about what to expect and when to seek medical attention.
Taking Rusfertide
Mimrylo is injected under the skin of the abdomen, the front of the thigh or the outer upper arm (upper arm only when a caregiver gives it) once a week, by the patient or a caregiver after training from the care team. The starting dose is 19 mg, and it can be raised in steps no sooner than every 2 weeks, up to 108 mg a week, to keep hematocrit below 45%. Weekly doses above 54 mg take 2 injections, and doses above 82 mg are split between day 1 and day 4 or 5. Each vial holds a powder that is mixed with the supplied diluent syringe and used within 4 hours. The dose is lowered for anemia of grade 2 or higher or other serious side effects[1].
Availability and cost
Only available as the brand-name product.
Help paying for Mimrylo
Pick your insurance to see which help fits. Drugmaker copay cards can't be used with Medicare, Medicaid or TRICARE; charity funds are the usual route there.
- Copay help
Takeda Oncology Co-Pay Assistance Program: eligible commercially insured patients 18 and older may pay as little as $0 per prescription. Valid up to 12 months and renewable; no income requirement. Not for Medicare, Medicaid, DoD, VA, TRICARE or state pharmaceutical assistance programs.
For: private insurance · source - Free medicine program
A Patient Assistance Program is listed for patients who are uninsured or whose insurance does not cover Mimrylo. Income limits are not published.
For: no insurance, underinsured · source - Other support
Free nurse-led injection training and welcome kits for enrolled patients.
The official page does not say who qualifies. Ask the program. · source
Good to know: Mimrylo was approved August 28, 2026. No annual copay maximum is stated on the page. The enrollment form lists the phone as 1-844-817-6468, Option 2, Monday to Friday, 8 AM to 8 PM ET. here2assist.com did not load, so mimrylo.com pages were used.
- From a charity · Blood Cancer United (formerly The Leukemia & Lymphoma Society)Clinical Trials Co-Pay Fund (all blood cancers) fundOpen
Pays for: Insurance premiums and treatment-related copays, deductibles and coinsurance, up to $3,500 per year. Requires health insurance (any kind).
- From a charity · Blood Cancer United (formerly The Leukemia & Lymphoma Society)Patient Aid Program fundOpen
Pays for: One-time $100 stipend for non-medical expenses (transportation, food, housing, utilities); no income or insurance requirement, up to $100 per year.
The foundation says: “CURRENT FUND STATUS: Open. Fund is currently Open.” - From a charity · CancerCare Co-Payment Assistance FoundationMyeloproliferative Neoplasms fundOpen
Pays for: Copays, coinsurance and deductibles for treatment, up to $7,000 per year. Requires Medicare, Medicaid or TRICARE.
The foundation says: “Status: Open. Grant Amount: $7,000 (Initial Grant Amount $7,000; Program CAP Amount $10,000)” - From a charity · TotalAssist (formerly PAN Foundation)Myeloproliferative Neoplasms fundOpen
Pays for: Out-of-pocket costs for approved medications, up to $9,500 per year. Requires health insurance (any kind).
- From a charity · The Assistance FundMyeloproliferative Neoplasms (MPN) fundWaitlist
Pays for: Copays, coinsurance, deductibles and other health-related expenses.
The foundation says: “WAITLIST — Accepting Waitlist Patients. TAF is currently accepting requests to join the enrollment waitlist for this program. Waitlists a…”
Access and eligibility
Approved for adults with polycythemia vera to treat erythrocytosis. Safety and effectiveness in children have not been established. The VERIFY trial enrolled people who needed frequent phlebotomies despite standard care. Women who could become pregnant should have a pregnancy test first and use effective contraception during treatment and for at least 30 days after the last dose. Breastfeeding is not advised during treatment and for 30 days after the last dose.
Source: MIMRYLO Patient Support (Takeda Oncology Here2Assist)
Access program details are provided for informational purposes and may vary based on insurance coverage, geographic location, and individual circumstances. Confirm current eligibility directly with the manufacturer or your specialty pharmacy.
Clinical trial results
VERIFY (NCT05210790) randomized 293 adults with polycythemia vera who needed frequent phlebotomies (at least 3 in 28 weeks or 5 in a year) despite standard care to Mimrylo or placebo for 32 weeks, added to their usual treatment. At the start, 44.7% were on phlebotomy alone and the rest also took hydroxyurea, interferon or ruxolitinib. A response, meaning no longer qualifying for a phlebotomy during weeks 20 to 32, occurred in 76.9% on Mimrylo vs 32.9% on placebo. Patients averaged 0.53 phlebotomies vs 1.82 over the 32 weeks, 62.6% vs 14.4% kept hematocrit below 45%, and fatigue scores improved by 1.79 points on Mimrylo while worsening by 0.19 points on placebo[1][8]. An earlier Phase 2 trial, REVIVE, was published in the New England Journal of Medicine in 2024[9].
Development history
Protagonist Therapeutics discovered rusfertide, which carried the code PTG-300[2][4]. Takeda and Protagonist announced a worldwide license and collaboration agreement on January 31, 2024[6]. The FDA received the application on December 29, 2025 and granted it priority review, and rusfertide also held Breakthrough Therapy, Orphan Drug and Fast Track designations[2][5]. Protagonist exercised its rusfertide opt-out right under the collaboration on April 28, 2026[7]. The FDA approved Mimrylo on August 28, 2026, and Takeda holds exclusive global development and commercialization rights[2][3][4]. As a condition of approval, the FDA requires at least 3 years of follow-up on long-term safety, including platelet counts, blood clots and progression to myelofibrosis or leukemia[2].
Explore Polycythemia Vera trials
Common questions about Rusfertide
▸What is Rusfertide (Mimrylo)?
A once-weekly injection under the skin, approved by the FDA on August 28, 2026 to treat erythrocytosis (too many red blood cells) in adults with polycythemia vera. The FDA described it as the first approved polycythemia vera treatment that mimics hepcidin, a hormone that regulates iron. In its main trial, 76.9% of patients no longer qualified for a phlebotomy during weeks 20 to 32, against 32.9% on placebo.
▸How does Rusfertide work?
Making red blood cells takes iron. Hepcidin is a natural hormone that regulates iron in the body. Rusfertide mimics hepcidin and blocks ferroportin, the body's iron transporter, which reduces the iron available for making red blood cells and lowers hematocrit, the share of the blood made up of red cells[1][3]. Because iron stays in storage instead of being used, ferritin (a measure of stored iron) rose on average from 21 to 124 mcg/L by week 32 in the main trial[1]. In that trial it was added to each patient's usual care, which could include phlebotomy, hydroxyurea, interferon or ruxolitinib[1].
▸What are the side effects of Rusfertide?
Mimrylo has no boxed warning and no contraindications. In the 32-week placebo-controlled part of the VERIFY trial, side effects more common than on placebo were injection site reactions (56% vs 33%), anemia (16% vs 4.1%), high platelet counts (8% vs 0.7%) and shortness of breath (8% vs 1.4%). Injection site reactions were mostly mild redness, itching, pain or swelling. Platelet counts rose an average of 31% within 4 weeks of starting, went above 600,000 per microliter in 36% of patients and above 1,000,000 in 6%, and generally leveled off by week 8, so blood counts are checked every 2 to 4 weeks after starting and after dose changes. Anemia led to dose reductions in 10% of patients. Based on animal studies, it may harm an unborn baby[1].
▸How is Rusfertide taken?
Mimrylo is injected under the skin of the abdomen, the front of the thigh or the outer upper arm (upper arm only when a caregiver gives it) once a week, by the patient or a caregiver after training from the care team. The starting dose is 19 mg, and it can be raised in steps no sooner than every 2 weeks, up to 108 mg a week, to keep hematocrit below 45%. Weekly doses above 54 mg take 2 injections, and doses above 82 mg are split between day 1 and day 4 or 5. Each vial holds a powder that is mixed with the supplied diluent syringe and used within 4 hours. The dose is lowered for anemia of grade 2 or higher or other serious side effects[1].
▸Is Rusfertide FDA approved?
Yes, Rusfertide (Mimrylo) is FDA approved (2026) for the treatment of Polycythemia Vera.
▸Does Mimrylo replace phlebotomy for polycythemia vera?
It reduced the need for phlebotomy in its main trial, but it was studied on top of usual care, not instead of it. In the VERIFY trial, patients on Mimrylo averaged 0.53 phlebotomies over 32 weeks vs 1.82 on placebo, and 76.9% no longer qualified for a phlebotomy during weeks 20 to 32. Your hematologist will keep checking your hematocrit and decide whether you still need phlebotomy or other treatment.
▸How do you take Mimrylo?
Mimrylo is a once-weekly injection under the skin that you or a caregiver give after your care team shows you how. Each dose comes as a powder in a vial that you mix with the supplied liquid and inject within 4 hours. The starting dose is 19 mg, and your doctor can raise it no more often than every 2 weeks, up to 108 mg a week, to keep hematocrit below 45%.
▸Does Mimrylo raise platelet counts?
It can. In trials, platelet counts rose an average of 31% within 4 weeks and generally leveled off by week 8; 36% of patients had counts above 600,000 per microliter. The label calls for blood counts every 2 to 4 weeks after starting and after dose changes, and some people may need their other treatment adjusted.
Sources and references
Every factual claim on this page is drawn from the public sources listed below. Click any reference to open the original document.
- U.S. National Library of Medicine, DailyMed. MIMRYLO (rusfertide) for injection, for subcutaneous use: prescribing information. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=101aff01-31ed-4841-a8b6-0a5a8503189b
- U.S. Food and Drug Administration · 2026-08-28. NDA 220605 approval letter. https://www.accessdata.fda.gov/drugsatfda_docs/appletter/2026/220605Orig1s000ltr.pdf
- U.S. Food and Drug Administration · 2026-08-28. FDA Approves First Drug of Its Kind for Polycythemia Vera, a Rare Blood Disorder. https://www.fda.gov/news-events/press-announcements/fda-approves-first-drug-its-kind-polycythemia-vera-rare-blood-disorder
- Takeda · 2026-08-28. Takeda Receives U.S. FDA Approval of MIMRYLO (rusfertide), Marking a Potential Shift in the Treatment Paradigm for Polycythemia Vera. https://www.takeda.com/newsroom/newsreleases/2026/fda-approval-mimrylo/
- Takeda · 2026-03-02. Takeda and Protagonist announce FDA accepts NDA and grants priority review for rusfertide. https://www.takeda.com/newsroom/newsreleases/2026/nda-rusfertide/
- Takeda · 2024-01-31. Takeda and Protagonist Therapeutics enter into worldwide license and collaboration agreement for rusfertide. https://www.takeda.com/newsroom/newsreleases/2024/takeda-and-protagonist-therapeutics-inc-enter-into-worldwide-license-and-collaboration-agreement-for-rusfertide-a-late-stage-rare-hematology-asset/
- Protagonist Therapeutics (SEC filing) · 2026-05-05. Protagonist Therapeutics first quarter 2026 results (Form 8-K exhibit). https://www.sec.gov/Archives/edgar/data/1377121/000110465926055629/tm2613550d1_ex99-1.htm
- ClinicalTrials.gov. A Phase 3 Study of Rusfertide in Patients With Polycythemia Vera (VERIFY). https://clinicaltrials.gov/study/NCT05210790
- New England Journal of Medicine · 2024. Rusfertide, a Hepcidin Mimetic, for Control of Erythrocytosis in Polycythemia Vera. https://www.nejm.org/doi/full/10.1056/NEJMoa2308809
- Takeda. Takeda Oncology Here2Assist for MIMRYLO. https://mimrylo.com/resources/here2assist