Rusfertide (Mimrylo)_Dosage, benefits & legal status
Also known as Mimrylo, PTG-300, rusfertide acetate
A lipid-tagged ring peptide that copies hepcidin and keeps iron in storage, so the bone marrow makes fewer red cells. In the phase 3 VERIFY trial, 76.9% stayed out of the range that calls for blood removal from weeks 20 to 32, against 32.9% on placebo.
Common vial size is what vendors typically sell, not a recommendation. Enter your own vial in the calculator.
What is Rusfertide (Mimrylo)?
Plain language first. The technical label stays, but it never stands alone.Overview
In polycythemia vera the bone marrow makes too many red cells, and many patients need blood drawn off (phlebotomy) again and again to keep their hematocrit below 45%. Rusfertide limits the iron the marrow can use, so it makes fewer red cells: in the 293-patient VERIFY trial, 76.9% stayed out of the phlebotomy range from weeks 20 to 32 against 32.9% on placebo, and phlebotomies over 32 weeks fell to 0.53 per patient against 1.82. It can push platelet counts up and red cells too low, so blood counts are checked every 2 to 4 weeks.
Rusfertide is a 17-residue synthetic hepcidin mimetic: an isovaleryl-capped, C-terminally amidated peptide closed by a Cys6 to Cys16 disulfide, with a palmitoyl chain attached to lysine 8 through a gamma-glutamyl spacer. It blocks ferroportin (SLC40A1), the only known cellular iron exporter, cutting the iron supply to red cell precursors so hematocrit falls without phlebotomy. Protagonist Therapeutics discovered it as PTG-300 and ran development through the phase 3 VERIFY trial and the US filing; Takeda licensed it worldwide in 2024 and markets it as Mimrylo.
What it's used for
A once-weekly injection under the skin for adults with polycythemia vera, to keep hematocrit below 45% and cut the need for phlebotomy. In the trial it was added to patients' usual treatment.
How does Rusfertide (Mimrylo) work?
What it does in the body, and where.Rusfertide copies hepcidin, the hormone that tells the body to hold iron back.
- 01Hepcidin's jobHepcidin binds ferroportin, the only known exporter of iron from cells, on gut lining cells, liver cells and iron-recycling macrophages, and shuts it down so less iron enters the blood.
- 02A stand-in hormoneRusfertide mimics that action and blocks ferroportin. Serum iron falls most 24 to 48 hours after a single dose and, at 41 and 54 mg, stays down to 96 hours.
- 03Fewer red cellsWith less iron reaching the bone marrow, red cell production slows and hematocrit falls, doing the job of phlebotomy. The iron is kept in storage rather than removed, so ferritin rises (21 to 174 mcg/L over 52 weeks in VERIFY), and anemia and high platelets are the effects that limit the dose.
What else is it used for?
Each group carries its own evidence level.Approved means regulators have cleared it for that purpose. Investigational means it is in trials. Early research means it is being studied and is not established.
Phase 3 (VERIFY)
FDA-approved- Human trial293 randomized: 76.9% against 32.9% free of phlebotomy eligibility from week 20 to 32 (risk difference 43.8%); hematocrit kept below 45% throughout in 62.6% against 14.4%.
- No dataThe endpoints were hematocrit control, phlebotomy counts and symptom scores; the label does not report the MFSAF symptom score result, though the 2025 ASCO abstract reports a significant improvement (p<0.03).
One year and crossover
FDA-approved- Human trial84.1% of 113 responders kept responding through week 52, 61.9% of continuously treated patients stayed free of phlebotomy eligibility from baseline to week 52, and 77.9% of 140 placebo patients responded after switching to rusfertide.
Safety in the trial
FDA-approved- Human trialOver 32 weeks, serious adverse events in 3.4% against 4.8% on placebo, none judged related to rusfertide; fatigue 15.2% against 15.8%.
- Human trialNew cancers were reported in 1 rusfertide patient against 7 on placebo; the label carries no cancer warning.
Mouse skin tumors and the 2021 hold
FDA-approved- Animal studyA 26-week rasH2 transgenic mouse study found benign and malignant subcutaneous skin tumors, and the FDA held all trials from September 17 to October 11, 2021.
- RegulatoryThe approved label reports a 6-month transgenic mouse study (up to 25 mg/kg a week) and a 2-year rat study (up to 3 mg/kg a week) as not carcinogenic; it does not discuss the 2021 finding or say how that mouse study relates to the 2021 one.
Phase 2 (REVIVE)
peer-reviewed-human- Human trial70 patients with phlebotomy-requiring polycythemia vera; after open-label dosing, a blinded randomized withdrawal from week 29 to 41 tested whether hematocrit control held without phlebotomy eligibility: 60% (18 of 30) responded on rusfertide against 17% (5 of 29) on placebo (p=0.002).
The 76.9% response rate is often quoted alone; 32.9% of placebo patients also responded, so the difference due to the drug is 43.8 percentage points (95% CI 33.5 to 54.2). The trial is reported as enrolling 293 patients; 293 were randomized (147 and 146), 145 rusfertide patients were dosed in the 32-week safety table, and 285 received rusfertide at some point, including those who crossed over from placebo. Both 56% and 47% appear in the label for injection-site reactions: 56% (against 33% on placebo) is the 32-week comparison and 47% covers all VERIFY exposure. Press figures over 52 weeks (injection-site reactions 47.4%, anemia 25.6%, fatigue 19.6%) differ from the label's 32-week table because the time window and patient counts differ. The phase 3 result is often credited to Takeda, the company that markets the drug; Protagonist Therapeutics discovered it and ran VERIFY and the US filing. It is not a pen or a ready-to-inject syringe: the powder is mixed with the supplied diluent and used within 4 hours, and doses above 82 mg are split within the week. The 2021 skin tumors came from a 26-week rasH2 mouse study that led to a hold of about a month; the label reports a 6-month transgenic mouse study and a 2-year rat study as not carcinogenic, without saying how that mouse study relates to the 2021 one, and has no cancer warning. Claims of a 20 or 21 amino acid peptide are wrong: the label's chemical name gives 17 residues, or 18 if the gamma-glutamyl spacer is counted.
The published record
Papers and trials about Rusfertide (Mimrylo)
23 papers tagged human · 9 not reviews or lab · 6 clinical trial publications
10 registered trials · 1 with posted results
Furthest stage reached: Approved in the US
Counted from Europe PMC indexing, not read by a person; a human tag can land on reviews, commentary or lab papers; clinical trial publications is the narrower count.
At a glance
Four things to know about Rusfertide (Mimrylo)
Evidence
FDA-approved
Category
Healing and recovery
Common vial
Varies
Half-life
About 28.6 hours
How much, and do you cycle it?
The range, and whether you take breaks.19 mg once a week to start, adjusted in steps from 9.5 to 108 mg (label), once a week. Weekly, long term FDA label
Given every week, with the dose stepped to keep hematocrit below 45%. In VERIFY, 84.1% of week-32 responders were still responding at week 52, and the study continues open-label to 156 weeks.
About 28.6 hoursFDA label
Mean 28.6 hours, plus or minus 11.3, in healthy participants after 19 mg under the skin. Levels peak at a median of 24 hours (4 to 48), and about 51% of the dose is absorbed. Steady state comes after about 3 weekly doses, with exposure (AUC) 1.6 times the first dose at 54 mg. Over 99% is bound to plasma proteins, and no intact drug was detected in urine. Exposure rose less than in proportion to dose from 9.5 to 54 mg.
Source: Mimrylo US prescribing information, section 12.3
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How is it given?
Dosing context and source notes.Supplied as a kit with its own diluent, and the label sets the volume, so there is nothing to work out here.
Label range: 9.5 up to 108 mg per week. Mimrylo US prescribing information, sections 2 and 16
Injected under the skin of the abdomen (at least 2 inches from the navel), the front of the thigh or the upper outer arm (arm by a caregiver only), rotating sites. The starting dose is 19 mg once a week. The dose steps are 9.5, 19, 28, 41, 54, 69, 82, 95 and 108 mg; it goes up one step at a time, after at least 2 weeks on the current dose, to bring or keep hematocrit below 45%. Doses above 54 mg take two injections, and doses above 82 mg are split between day 1 and day 4 or 5 of the week. The dose drops one step for grade 2 or worse anemia or a drug-related grade 3 or worse side effect, and treatment stops if this happens at 9.5 mg. Blood counts are checked every 2 to 4 weeks when starting and after changes. A weekly dose 1 to 4 days late is given at once and the schedule resumes; more than 4 days late, it is given at once and the next dose follows 3 days later. No adjustment for kidney impairment or moderate liver impairment; severe liver impairment was not studied. Supplied as single-dose vials of white powder (9.5, 19, 28, 41 or 54 mg), each carton with a prefilled glass syringe of 0.6 mL diluent, an adapter and a needle; it is not a pen. The mixed solution is used within 4 hours, and cartons are kept at 20 to 25°C, not frozen, away from light.
How do you store it?
Before mixing, and after.Follow the storage on the product label.
Rusfertide (Mimrylo) is supplied as a finished product, so its label sets the storage. Pens, prefilled syringes, implants, tablets and ready-made solutions are used as supplied. Kits that include a powder are mixed just before the dose and usually used straight away, not kept for weeks. Many injectable products go in the fridge and must not be frozen, while others are kept at room temperature, so check the pack or ask the pharmacist.
What are the side effects and cautions?
Known cautions and warnings for this compound.Solubility, computed: 47% charged residues, 41% hydrophobic. Water usually sufficient.
A first-pass rule from peptide manufacturers' guidance. It does not account for disulfide bridges, salt form or how the powder was dried, and it predicts what should be easy rather than what will happen in your vial.
Who should avoid it
- None on the US label
- Pregnancy: rat and rabbit studies showed malformations and fetal loss, so a pregnancy test is advised before starting, with contraception during treatment and for at least 30 days after
- Breastfeeding not recommended during treatment and for 30 days after the last dose, as it may impair the infant's iron absorption
- Children: safety and effectiveness not established
- Severe liver impairment (Child-Pugh C) not studied
Stop and get help
- A positive pregnancy test: treatment is stopped because of possible harm to the fetus
- Breathlessness, marked tiredness or dizziness, possible anemia that the label handles by lowering the dose one step
Common effects
- Injection-site reactions 56% against 33% on placebo over weeks 0 to 32; across all VERIFY exposure, redness 27%, itching 17%, pain 15% and swelling 8%, with 0.7% stopping
- Anemia 16% against 4.1%, the main reason for dose reductions (10% of patients)
- Raised platelets 8% against 0.7% as a reported side effect; on blood tests, 36% passed 600 x 10^9/L and 6% passed 1,000 x 10^9/L, usually leveling off by week 8
- Shortness of breath 8% against 1.4%; antibodies to the drug in 34% (97 of 282), all at low titers, with no apparent effect on drug levels, benefit or safety
Where this page says nothing is established, that means nobody has studied it, not that a compound is safe.
Is Rusfertide (Mimrylo) approved?
And where the numbers on this page come from.Yes. Rusfertide (Mimrylo) is FDA approved and available on prescription in the United States.
- Approval statusFDA-approved
- RouteUnder the skin (weekly injection)
- Checked18 October 2026
- DoseFrom the drug label. The manufacturer tested this range and a regulator reviewed it.
- Vial sizeFrom what vendors typically list; not a recommendation.
- SourcesMimrylo US prescribing information (Takeda, 2026)DailyMed, Mimrylo (rusfertide) kitDrugs@FDA, NDA 220605Takeda, FDA approval of Mimrylo (August 28, 2026)FDA GSRS substance record, rusfertide (UNII XM71MYX0IQ)FDA GSRS codes, rusfertideKuykendall AT et al., Journal of Clinical Oncology 2025;43(17_suppl):LBA3 (VERIFY)Kremyanskaya M et al., New England Journal of Medicine 2024;390:723-735 (REVIVE)Protagonist Therapeutics Form 10-Q, quarter ended June 30, 2026Takeda and Protagonist license agreement (January 31, 2024)Protagonist, FDA clinical hold (September 17, 2021)Fierce Biotech, FDA lifts rusfertide hold (October 2021)OncLive, FDA approves rusfertide for polycythemia vera (August 28, 2026)Drugs.com, rusfertide NDA accepted with priority review (March 2, 2026)
What has happened recently
Protagonist Therapeutics discovered rusfertide as PTG-300. On September 17, 2021, the FDA placed all rusfertide trials on clinical hold after a 26-week study in rasH2 transgenic mice found benign and malignant subcutaneous skin tumors; the lifting of the hold was announced on October 11, 2021, after Protagonist supplied patient safety reports and updated investigator brochures and consent forms. Takeda licensed worldwide rights on January 31, 2024, paying $300 million upfront, with Protagonist responsible for development through the phase 3 trial and US approval. Rusfertide held orphan drug and Fast Track designations, and Breakthrough Therapy designation from August 2025. The NDA was submitted in December 2025 (announced January 5, 2026) and accepted with priority review on March 2, 2026. On April 28, 2026, Protagonist opted out of the US profit share in exchange for $200.0 million plus a $200.0 million opt-out fee and worldwide royalties of 14% to 29%. The FDA approved Mimrylo on August 28, 2026 (NDA 220605, a new molecular entity with priority review and orphan status) for erythrocytosis in adults with polycythemia vera; Takeda Pharmaceuticals America markets it. It is not approved outside the US; Takeda says it is working with regulators elsewhere. A separate orphan designation for beta-thalassemia was withdrawn.
You can compare this against the whole library, or read how to check a seller.
What else is like Rusfertide (Mimrylo)?
Others in Healing and recovery, side by side.If you're weighing Rusfertide (Mimrylo), it's worth reading Sincalide (Kinevac), ORJ-001 (NP-201), and BPC-157 in the same class.
A lipid-tagged ring peptide that copies hepcidin and keeps iron in storage, so the bone marrow makes fewer red cells. In the phase 3 VERIFY trial, 76.9% stayed out of the range that calls for blood removal from weeks 20 to 32, against 32.9% on placebo.
- Dose
- 19 mg once a week to start, adjusted in steps from 9.5 to 108 mg (label)
- How often
- Once a week
The last eight amino acids of cholecystokinin, the hormone that empties the gallbladder. FDA-approved as a diagnostic since 1976; it is not an appetite drug, and a pill acting on the same receptor failed to cause weight loss.
- Dose
- 0.02 mcg/kg over 30 to 60 seconds, with a second dose of 0.04 mcg/kg if needed (label)
- How often
- Once per test
A synthetic 19-amino-acid peptide meant to switch on beta-1 integrin and help the lining of the lungs repair itself. Its phase 2 in pulmonary fibrosis screened its first patient in October 2026.
- Dose
- 200 or 400 mg twice weekly (phase 2 trial)
- How often
- Twice weekly (phase 2 trial)
A popular healing peptide for injuries, gut, and joint or tendon pain.
- Dose
- 0.25 up to 0.5 mg per dose (start low, increase slowly)
- How often
- 1-2x daily
Guides for this compound
- How to Reconstitute a Peptide
Mix peptide powder with bacteriostatic water, step by step.
- How to Read an Insulin Syringe
Read the units, convert to millilitres, and draw the exact dose.
- mcg vs mg: The Peptide Dosing Mistake to Avoid
Your vial says mg and your protocol says mcg. Here is the conversion and how to check it.
Sources
- Mimrylo US prescribing information (Takeda, 2026)(2026)Indication; 19 mg start, 9.5 to 108 mg weekly; half-life 28.6 hours; VERIFY 76.9% against 32.9% (common risk difference 43.8%, 95% CI 33.5% to 54.2%); chemical name with the Cys6 to Cys16 ring.
- DailyMed, Mimrylo (rusfertide) kit(2026)NDA220605, Takeda Pharmaceuticals America; marketing start August 28, 2026; adverse reaction table; vial strengths, NDCs and storage.
- Drugs@FDA, NDA 220605(2026)Approved August 28, 2026; type 1 new molecular entity; priority review; orphan.
- Takeda, FDA approval of Mimrylo (August 28, 2026)(2026)First-in-class hepcidin mimetic; Takeda holds worldwide rights and is working with regulators outside the US.
- FDA GSRS substance record, rusfertide (UNII XM71MYX0IQ)(2026)C114H181N27O28S2, MW 2441.9577; the SMILES matches the structure in the label's chemical name.
- FDA GSRS codes, rusfertide(2026)CAS 1628323-80-7; INN 11456; FDA orphan designations for polycythemia vera (designated) and beta-thalassemia (withdrawn).
- Kuykendall AT et al., Journal of Clinical Oncology 2025;43(17_suppl):LBA3 (VERIFY)(2025)293 randomized; 76.9% against 32.9% responded; serious adverse events 3.4% against 4.8%, none judged related; new cancers in 1 against 7 patients.
- Kremyanskaya M et al., New England Journal of Medicine 2024;390:723-735 (REVIVE)(2024)Phase 2 in 70 patients with phlebotomy-requiring polycythemia vera, with a blinded randomized withdrawal from week 29 to 41: 60% (18 of 30) responded on rusfertide against 17% (5 of 29) on placebo (p=0.002).
- Protagonist Therapeutics Form 10-Q, quarter ended June 30, 2026(2026)US profit-share opt-out April 28, 2026; royalties 14% to 29%; Breakthrough Therapy August 2025; milestones still due on first EU and Japan approvals.
- Takeda and Protagonist license agreement (January 31, 2024)(2024)$300 million upfront; Protagonist responsible for development through phase 3 and US approval; Takeda leads global sales.
- Protagonist, FDA clinical hold (September 17, 2021)(2021)Hold on all trials after benign and malignant subcutaneous skin tumors in a 26-week rasH2 transgenic mouse study.
- Fierce Biotech, FDA lifts rusfertide hold (October 2021)(2021)Hold removed after patient safety reports and updated investigator brochures and consent forms.
- OncLive, FDA approves rusfertide for polycythemia vera (August 28, 2026)(2026)84.1% of responders still responding at week 52; 77.9% of placebo patients responded after crossing over.
- Drugs.com, rusfertide NDA accepted with priority review (March 2, 2026)(2026)All four key secondary endpoints met; over 52 weeks, injection-site reactions 47.4%, anemia 25.6%, fatigue 19.6% and serious adverse events 8.1%.
Beyond these, 30 records are indexed. Browse the records