TMPRSS6 inhibition and hepcidin-mediated iron restriction in PV
Current understanding
TMPRSS6 (matriptase-2) is a hepatic serine protease that cleaves hemojuvelin (HJV), dampening BMP/SMAD signaling and thereby suppressing HAMP (hepcidin) transcription; antisense knockdown of TMPRSS6 raises hepcidin, sequesters iron in macrophages/enterocytes, and limits iron supply to erythroid precursors. In polycythemia vera, where JAK2V617F-driven erythropoiesis depends on iron availability and phlebotomy is the mainstay of hematocrit control, pharmacologic TMPRSS6 inhibition (sapablursen, an LICA-conjugated ASO) is being tested as a first-in-class strategy to reduce phlebotomy burden by re-imposing iron restriction upstream of erythroid output. This mechanism is mechanistically complementary to ACVR1-axis modulation but acts on the opposite side of the hepcidin-regulatory circuit and on the opposite clinical problem (erythrocytosis in PV rather than anemia in MF).
Evidence log
- 2026-08-31 — FDA Approves First-of-its-Kind Drug for Polycythemia Vera (Rusfertide/Mimrylo): cross-connection with acvr1-hepcidin-axis: Rusfertide’s FDA approval establishes direct hepcidin mimicry as a validated PV therapy, complementing TMPRSS6 inhibition which raises endogenous hepcidin — both converge on hepcidin-mediated iron restriction to control erythrocytosis. (novelty: 4)
- 2026-06-15 — A Study of Rusfertide in Japanese Adults With Polycythemia Vera: cross-connection with acvr1-hepcidin-axis: Rusfertide (direct hepcidin mimetic) and sapablursen (TMPRSS6 ASO) converge on the same goal — raising effective hepcidin tone to restrict iron-driven erythrocytosis in PV — via complementary entry points into the hepcidin regulatory circuit. (novelty: 3)
- 2026-06-01 — A Study to Evaluate Sapablursen (Formerly ISIS 702843, IONIS-TMPRSS6-LRx) in Patients With Polycythemia Vera: cross-connection with acvr1-hepcidin-axis: Both pathways converge on hepatic hepcidin transcription via BMP/SMAD signaling but are exploited in opposite directions: ACVR1 inhibition lowers hepcidin to relieve iron restriction in MF anemia, while TMPRSS6 ASO knockdown raises hepcidin to impose iron restriction in PV erythrocytosis. (novelty: 4)