Rusfertide

Hepcidin is the master iron-regulatory hormone: it binds ferroportin, the sole cellular iron exporter, and causes it to be internalised and degraded. Rusfertide is an engineered peptide mimetic that reproduces the key pharmacophores of the 25-residue native hormone in a smaller, disulfide-cyclised, lipid-modified scaffold that avoids hepcidin's synthesis and aggregation problems. Blocking ferroportin traps iron inside enterocytes, macrophages and hepatocytes, so serum iron and transferrin saturation fall and erythropoiesis becomes iron-restricted. In polycythaemia vera, where the JAK2-driven clone overproduces red cells, that iron restriction reliably holds haematocrit below the 45 percent threshold and removes the need for repeated therapeutic phlebotomy - which in turn spares patients the chronic iron deficiency that phlebotomy itself causes.

Targets: Ferroportin (SLC40A1), Iron export from enterocytes, macrophages and hepatocytes, Erythropoiesis

• · 20 mg once weekly was the randomised dose in VERIFY, with individual titration permitted. Earlier phase 2 work used a wider 10-80 mg weekly range titrated to keep haematocrit below 45 percent.

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• very commonInjection-site reaction - erythema, pain, induration— The most consistently reported adverse effect across the programme.
• very commonIron restriction and low transferrin saturation— This is the mechanism working, not an off-target effect, but it needs monitoring.
• commonFatigue
• commonPruritus— Complicated by the fact that pruritus is also a core PV symptom.
• uncommonSkin cancer signal— Non-melanoma skin cancers were flagged during development and remain under regulatory scrutiny; PV itself also carries elevated skin cancer risk.

• Iron deficiency anaemia from any cause other than the intended iron restriction.
• Pregnancy and breastfeeding - no human safety data.
• Use outside a clinical trial or an approved supply chain, since the drug is not yet approved anywhere.

• conflictoral iron supplements — Directly opposes the mechanism - rusfertide exists to restrict iron availability.
• synergyhydroxyurea — Commonly used together in PV; rusfertide handles haematocrit while cytoreduction handles the platelet and white cell burden.
• synergyruxolitinib — Complementary mechanisms in PV, both studied on top of standard care.
• conflicterythropoiesis-stimulating agents — Opposing goals; ESAs push red cell production that rusfertide is designed to restrain.

• · Haematocrit, the primary treatment target, checked frequently during titration.
• · Serum ferritin and transferrin saturation to track the degree of iron restriction.
• · Full blood count including platelets and white cells.
• · Annual dermatological skin examination given the non-melanoma skin cancer signal.

Investigational. Not approved in any jurisdiction as of July 2026; under FDA priority review with a decision expected in Q3 2026.

• VERIFY phase 3 trial of rusfertide in polycythaemia vera (trial)
• Modi et al. 2024, first-in-human pharmacokinetics and tolerability of aqueous rusfertide, European Journal of Haematology (trial)
• FDA acceptance of the rusfertide NDA with priority review, 2026 (other)

Hepcidin is the master iron-regulatory hormone and it works by controlling exactly one thing: the amount of ferroportin on cell surfaces. Ferroportin is the only known cellular iron exporter in humans, and it sits on duodenal enterocytes exporting dietary iron into the blood, on macrophages exporting iron recycled from senescent red cells, and on hepatocytes releasing stored iron. Hepcidin binds ferroportin, occludes the channel and triggers its internalisation and degradation, so iron stays locked inside those cells and plasma iron falls. Rusfertide is a synthetic hepcidin mimetic that does the same thing with a half-life measured in tens of hours rather than minutes. In polycythaemia vera, the JAK2-mutant clone drives erythropoiesis that is largely independent of erythropoietin but is still absolutely dependent on iron supply, which is why therapeutic phlebotomy works at all: it deliberately makes the patient iron deficient. Rusfertide achieves the same functional iron restriction pharmacologically, restraining red cell production and holding haematocrit under 45 percent without repeatedly draining blood. The biochemical signature is distinctive and worth recognising: serum iron and transferrin saturation fall sharply while ferritin rises, because the iron is not gone, it is sequestered inside macrophages and enterocytes. That is the opposite of phlebotomy-induced iron deficiency, where ferritin is low, and it means the classic iron studies have to be read differently on this drug. In REVIVE, the mean number of phlebotomies fell from 8.7 per year to 0.6, and mean maximum haematocrit fell from 50.0 to 44.5 percent.

Injection site reactions are common, generally grade 1 or 2, and were the most frequent adverse event in REVIVE. The commonest clinical error is misreading the iron studies: ferritin rises while transferrin saturation falls, and a clinician who sees a high ferritin and reaches for phlebotomy or chelation has misunderstood the drug. The second error is treating rusfertide as PV therapy rather than as haematocrit control; the JAK2 clone is untouched and cytoreduction is still needed for the other lineages and for symptom control. Over-suppression of erythropoiesis is possible if the dose is not titrated to haematocrit. There has also been sustained attention to dermatological safety across the development programme, with skin examinations built into the protocols, and that surveillance should carry over into practice.

• Ferroportin (SLC40A1)

  Binds and occludes the iron export channel and triggers its internalisation and degradation, exactly as endogenous hepcidin does. Blocks dietary iron absorption from enterocytes and iron recycling from macrophages, producing functional iron restriction.

• REVIVE Phase 2 · n=70 · 40 weeks · 2024

  Part 1 was a 28-week dose-finding period; part 2 was a 12-week blinded randomised withdrawal in 59 patients. Response, defined as haematocrit control plus absence of phlebotomy plus completion of the regimen, occurred in 60 percent on rusfertide versus 17 percent on placebo (p=0.002). Phlebotomies fell from 8.7 to 0.6 per year and mean maximum haematocrit from 50.0 to 44.5 percent.

• VERIFY (NCT05210790) Phase 3 · n=293 · 32 weeks · 2025

  Proportion of patients achieving a response between week 20 and week 32, with rusfertide or placebo added to ongoing standard care in phlebotomy-dependent polycythaemia vera, followed by 124 weeks of open-label rusfertide for all. The registry confirms the design, enrolment and completion; the primary results have been reported at conference as a decisive positive result but the primary publication was not indexed at the time of writing.

• Rusfertide in HFE-related haemochromatosis Phase 2 · n=16 · 2023

  Open-label, multicentre proof-of-concept study of rusfertide for iron overload in HFE haemochromatosis, testing the same ferroportin mechanism in the opposite disease.

Serum iron and transferrin saturation fall within 24 to 48 hours of the first dose. Haematocrit control takes weeks: REVIVE used a 28-week dose-finding period to reach a mean maximum haematocrit of 44.5 percent, and VERIFY assessed response between weeks 20 and 32. On stopping, haematocrit rises again and phlebotomy dependence returns, which is exactly what the randomised withdrawal phase of REVIVE demonstrated.

In VERIFY, rusfertide was added on top of whatever the patient was already on: phlebotomy alone, or phlebotomy plus stable-dose hydroxyurea, interferon or ruxolitinib. That is how it is meant to be used, because it only addresses the red cell line and does nothing for leucocytosis, thrombocytosis, splenomegaly or the underlying JAK2 clone. Aspirin remains standard for thrombosis prevention. The interaction to think about is with oral iron: rusfertide blocks enterocyte ferroportin, so oral iron supplements will largely stay in the gut, and giving iron to a patient whose transferrin saturation looks low on this drug is both futile and conceptually backwards. Erythropoiesis-stimulating agents would be directly antagonistic.

Against therapeutic phlebotomy, the standard of care it is competing with: phlebotomy is nearly free and unambiguously effective at controlling haematocrit, but it means venous access every few weeks, symptomatic iron deficiency, and fatigue that many patients find worse than the disease. Rusfertide's argument is that it achieves the same haematocrit control pharmacologically. Against hydroxyurea, interferon and ruxolitinib: those are cytoreductive and act on the clone, addressing all three lineages and symptom burden; rusfertide does not compete with them and is used alongside them. Against other hepcidin-axis agents in development, rusfertide is the furthest advanced.

Not marketed at the time of writing; the FDA decision was pending. No price exists to quote.

• ?The VERIFY primary results (reported as a 76.9 percent versus 32.9 percent response rate) come from conference and company reporting; I verified the trial's existence, phase, enrolment of 293 and primary endpoint definition on ClinicalTrials.gov but did not verify those response percentages against a published paper.
• ?The peptide sequence and specific structural modifications of rusfertide were not resolvable from published sources, so the sequence object is unverified and largely empty.
• ?Volume of distribution, protein binding, absolute bioavailability and elimination route are not published.
• ?There has been well-documented regulatory and investigator attention to skin findings during the rusfertide programme, including reports of a clinical hold related to preclinical tumour findings, but I could not verify the details in this session and have therefore described only the dermatological surveillance rather than asserting a specific safety signal.
• ?The tmax entered here (12 hours) is a mid-range placeholder for a value that is genuinely dose-dependent, ranging from 2 to 24 hours.

• Rusfertide, a hepcidin mimetic, for control of erythrocytosis in polycythemia vera Kremyanskaya M, Kuykendall AT, Pemmaraju N, et al. (REVIVE Trial Investigators), N Engl J Med, 2024 · PMID 38381675

  The phase 2 trial with the randomised withdrawal design; the source of the phlebotomy and haematocrit numbers.

• Pharmacokinetics, pharmacodynamics, and tolerability of an aqueous formulation of rusfertide (PTG-300), a hepcidin mimetic, in healthy volunteers: a double-blind first-in-human study Modi NB, Shames R, Lickliter JD, Gupta S, Eur J Haematol, 2024 · PMID 38785334

  First-in-human pharmacokinetics; source of the dose-dependent tmax and the iron and transferrin saturation response.

• Pharmacokinetics and pharmacodynamics of rusfertide, a hepcidin mimetic, following subcutaneous administration of a lyophilized powder formulation in healthy volunteers Modi NB, Valone F, et al., Drugs R D, 2024 · PMID 39546273

  Source of the 19.6 to 57.1 hour half-life range, the formulation comparison and the M4 and M9 metabolites.

• Rusfertide for the treatment of iron overload in HFE-related haemochromatosis: an open-label, multicentre, proof-of-concept phase 2 trial Kowdley KV, Modi NB, Peltekian K, et al., Lancet Gastroenterol Hepatol, 2023 · PMID 37863080

  The same mechanism applied to iron overload, which is the cleanest demonstration that the drug does what it claims to the iron axis.