Peptide education
Rusfertide
Mimrylo · PTG-300
Rusfertide is a peptide that acts like hepcidin, a hormone involved in iron regulation. The FDA-approved product Mimrylo treats excess red blood cell production in adults with polycythemia vera.
In a phase 3 trial, more participants receiving rusfertide met a defined phlebotomy-eligibility endpoint than those receiving placebo. Blood-count monitoring and the label's safety warnings remain important.
Overview
Quick answer
Approval applies to a specific prescription product and adult indication. It does not establish that a research product is equivalent or that rusfertide treats other causes of high red blood cell counts.
What is it approved to treat?
Mimrylo is FDA-approved for erythrocytosis in adults with polycythemia vera.
What did the phase 3 trial measure?
The label summarizes response as no phlebotomy eligibility during weeks 20 to 32. The trial report also counted specified events, such as certain missed blood-count checks or stopping early, as nonresponse.
What are the main risks?
The label warns about rising platelet counts, injection-site reactions, and potential fetal harm. Anemia was also common in the randomized trial.
Evidence
Evidence snapshot
The trial reported response with rusfertide versus placebo between weeks 20 and 32. Response required no phlebotomy eligibility, and specified events such as early withdrawal counted as nonresponse.
Continued rusfertide had more responses than placebo after an open-label period.
The label describes anemia and new or worsening thrombocytosis, among other risks.
Claims
Common claims vs evidence
| Claim | Human evidence | Mechanistic evidence | Verdict |
|---|---|---|---|
| Rusfertide is approved for any condition with high hematocrit. | VERIFY studied 293 adults with polycythemia vera who had needed frequent phlebotomies. | Rusfertide restricts iron availability by acting on ferroportin. | FDA approval is for erythrocytosis in adults with polycythemia vera; approval and trial evidence should not be generalized to other causes or products. |
| The trial proves it prevents blood clots. | VERIFY assessed response using phlebotomy eligibility and counted specified events as nonresponse. | That endpoint does not by itself prove a reduction in thrombosis. |
Bottom line
Main takeaway
This is a prescription treatment for a specific blood disorder, not a general iron supplement.
Dosing and monitoring belong with the treating clinician and the current prescribing information.
Distinguish the phase 3 randomized endpoint from phase 2 before-and-after observations.
Identity
What it is
Rusfertide is a synthetic cyclic peptide supplied in the approved product as rusfertide acetate.
Use context
Routes, doses, and cycle patterns
The approved label specifies a clinician-adjusted regimen for the indicated adult population.
Human studies and product labels
Mimrylo prescribing information
- Context
- FDA-approved product for erythrocytosis in adults with polycythemia vera
- Route
- Subcutaneous
- Amount
- Starting dose 19 mg; labeled weekly range 9.5 to 108 mg
- Frequency
- Weekly schedule, with higher weekly amounts divided as specified in the label
Dose adjustments depend on effectiveness and safety; the label calls for complete blood count monitoring during initiation and dose changes.
Research
Research evidence
The phase 3 VERIFY trial compared rusfertide with placebo in adults who needed frequent phlebotomy despite ongoing care. The earlier REVIVE study included open-label dose finding followed by randomized withdrawal.
| Study / evidence area | Population | Design | Product context | Main outcome | Limitations | Weight |
|---|---|---|---|---|---|---|
| VERIFY | 293 adults with polycythemia vera and frequent prior phlebotomy | Phase 3, randomized, double-blind, placebo-controlled | Rusfertide or placebo added to ongoing care | Between weeks 20 and 32, 113 of 147 rusfertide recipients and 48 of 146 placebo recipients met the response definition, which required no phlebotomy eligibility and no specified events counted as nonresponse. | This was a hematocrit-based endpoint, not a direct demonstration of fewer blood clots. | Randomized controlled trial |
| REVIVE | 70 adults entered dose finding; 59 entered randomized withdrawal | Phase 2 open-label dose finding, then blinded withdrawal | Rusfertide added to existing care | Phlebotomy frequency was lower during open-label treatment than before treatment, and response favored continued drug during withdrawal. | The before-and-after comparison was not randomized; withdrawal followed treatment exposure. | Mixed open-label and randomized evidence |
Use context
Reported use context
Study and label details describe specific medical contexts, not a personalized prescription.
Study and label context
Participants started at 19 mg once weekly, with subsequent adjustment to control hematocrit during the 32-week randomized period.
The regimen was studied with ongoing standard care and monitoring in adults with polycythemia vera.The study used weekly doses from 10 to 120 mg, adjusted during dose finding, followed by randomized withdrawal.
This was a study protocol and its dose range is not the approved label's dosing range.Cautions
Safety and unknowns
- New or worsening thrombocytosis and anemia require blood-count monitoring.
- Injection-site reactions occurred in the randomized trial.
- The label warns of potential fetal harm based on animal data and advises against breastfeeding during treatment and for a period after the last dose.
- The trial endpoint does not establish the size of any effect on long-term blood-clot outcomes.
Product quality
Product identity and quality
Mimrylo is an FDA-approved sterile prescription formulation; a research-labeled product is not automatically equivalent.
Approved formulation
The trial and label apply to the specified product and clinical setting.
Sterility and identity
A peptide name alone does not establish the quality of an injectable product.
Mechanism
How it is proposed to work
Rusfertide acts like hepcidin and reduces the iron available for making red blood cells.
It binds ferroportin and reduces iron release into the circulation.
Details
Technical details
Sources
References
- 1.
FDA. Mimrylo prescribing information
NCT05210790
Official U.S. label, including indication, dose modifications, warnings, and VERIFY results.
- 2.
FDA. FDA approval of Mimrylo for polycythemia vera
FDA announcement of approval for the specified adult indication.
- 3.
PubMed. VERIFY phase 3 trial of rusfertide in polycythemia vera
doi:10.1200/JCO-26-00992 PMID:42868322 NCT05210790
Randomized trial report describing the response definition and intercurrent events.
- 4.
ClinicalTrials.gov. VERIFY statistical analysis plan
NCT05210790
Filed analysis plan describes the events classified as nonresponse for the primary endpoint.
- 5.
PubMed. Rusfertide for control of erythrocytosis in polycythemia vera
doi:10.1056/NEJMoa2308809 PMID:38381675 NCT04057040
Phase 2 study with an open-label dose-finding period and randomized withdrawal.
- 6.
PubMed. REVIVE study abstract
doi:10.1056/NEJMoa2308809 PMID:38381675 NCT04057040
PubMed record and abstract for the phase 2 study; the full journal article is separately linked.