Polycythemia vera (PV) is a rare BCR-ABL-negative myeloproliferative neoplasm characterized by uncontrolled red blood cell production driven by mutations in the JAK2 gene (most commonly JAK2 V617F). Elevated hematocrit levels drive increased thrombotic risk, and standard of care has historically relied on therapeutic phlebotomy plus cytoreductive agents (hydroxyurea, ruxolitinib, interferons) that either do not directly regulate iron availability or are dose-limited by tolerability.
The treatment landscape shifted Friday August 28, 2026 with FDA approval of Takeda-Protagonist's Mimrylo (rusfertide), a first-in-class subcutaneous synthetic hepcidin mimetic peptide that mimics the activity of natural hepcidin to limit iron availability for erythropoiesis and constrain red blood cell overproduction. Approval was based on the Phase 3 VERIFY trial in which 76.9% of patients on rusfertide plus standard of care were phlebotomy-free through Week 32 versus 32.9% on placebo plus standard of care. Adverse events were generally low-grade and included injection-site reactions, anemia, and fatigue. Mimrylo is projected by Jefferies at $2 billion peak sales.
Other programs in polycythemia vera coverage: Incyte's ruxolitinib (Jakafi) remains the mainstay JAK1/JAK2 inhibitor; PharmaEssentia's Besremi (ropeginterferon alfa-2b-njft) is an approved pegylated interferon; and multiple next-generation JAK-selective and MDM2 inhibitors are in earlier development. Stories here cover trial readouts, real-world evidence, and the hepcidin mimetic class expansion. See #rusfertide, #protagonist-therapeutics, and #takeda for adjacent threads.
Takeda (NYSE: TAK) and Protagonist Therapeutics (NASDAQ: PTGX) announced Friday August 28, 2026 FDA approval of Mimrylo (rusfertide, a first-in-class subcutaneous synthetic hepcidin mimetic peptide) for the treatment of erythrocytosis in adults with polycythemia vera (PV), a rare BCR-ABL-negative myeloproliferative neoplasm in which uncontrolled red blood cell production drives increased thrombotic risk. Approval was based on the Phase 3 VERIFY trial (n=293) in which 76.9% of patients on rusfertide plus standard of care were phlebotomy-free through Week 32 versus 32.9% on placebo plus standard of care, with statistically significant improvements in hematocrit control and patient-reported fatigue and symptom burden. Adverse events were generally low-grade and included localized injection-site reactions (55.9%), anemia (15.9%), and fatigue (15.2%). Mimrylo will be commercialized by Takeda under the 2024 worldwide license and collaboration agreement with Protagonist and will ship within 48 hours. Jefferies analysts project peak sales potential of $2 billion. The mechanism (mimicking the natural iron-regulator hepcidin to constrain iron availability for erythropoiesis) is the first commercial validation of the hepcidin mimetic peptide class after more than a decade of academic development.
Silence Therapeutics (NASDAQ: SLN) announced the closing of its upsized $201.3 million underwritten public offering of American Depositary Shares. Terms: priced August 11 at $13.50 per ADS for 12,962,963 ADSs. The underwriters (Jefferies, Morgan Stanley, Cantor Fitzgerald, and William Blair as joint book-running managers) fully exercised their 30-day option to purchase an additional 1,944,444 ADSs, bringing the total offering to 14,907,407 ADSs and gross proceeds to approximately $201.3 million. The financing follows the August 10 Phase 2 SANRECO trial win in polycythemia vera with divesiran (first-in-class TMPRSS6-targeting siRNA that increases hepcidin production to restrict iron availability to bone marrow) achieving an 88% response rate versus 19% on placebo (P<0.0001, 69% placebo-adjusted response rate) in 48 phlebotomy-dependent patients over 36 weeks. Use of proceeds: advance divesiran into Phase 3 (planned initiation H1 2027 evaluating Q12W dosing versus placebo) plus broader pipeline progression including hepatic-target GalNAc-conjugated siRNA portfolio across TMPRSS6, complement component 3 (SLN-124/SLN-501), and other liver-targeted RNAi candidates. Divesiran has FDA Fast Track and Orphan Drug designations for polycythemia vera.
Silence Therapeutics (NASDAQ: SLN) closed its upsized $175 million underwritten public offering of American Depositary Shares (ADSs) following the August 10, 2026 Phase 2 SANRECO trial win in polycythemia vera. Trial anchor: divesiran achieved 88% response versus 19% on placebo (P<0.0001, 69% placebo-adjusted response rate) in 48 phlebotomy-dependent patients over 36 weeks. Offering mechanics: priced August 11 at $13.50 per ADS for 12,962,963 ADSs. The underwriters (Jefferies, Morgan Stanley, Cantor Fitzgerald, and William Blair as joint book-running managers) fully exercised their 30-day overallotment option for an additional 1,944,444 ADSs, bringing the total offering to 14,907,407 ADSs and gross proceeds to approximately $175 million. The financing provides the capital to advance divesiran into Phase 3 (planned initiation H1 2027) plus broader pipeline progression including the GalNAc-conjugated hepatic-target siRNA portfolio across TMPRSS6, complement component 3 (SLN-124/SLN-501), and other hepatic and extrahepatic targets. Divesiran has FDA Fast Track and Orphan Drug designations for polycythemia vera; the transferable-voucher secondary market and the recently completed Arrowhead $215 million Priority Review Voucher purchase provide comparable references for the broader siRNA regulatory-instrument landscape.
Silence Therapeutics (NASDAQ: SLN) announced positive topline results from the Phase 2 SANRECO trial of divesiran, a first-in-class TMPRSS6-targeting siRNA product candidate developed from the company's proprietary mRNAi GOLD platform. The trial enrolled 48 phlebotomy-dependent adults with polycythemia vera (PV) and evaluated divesiran 6 mg/kg administered subcutaneously every 6 weeks (Q6W) or every 12 weeks (Q12W) versus placebo over a 36-week randomized double-blind period. Results: 88% of divesiran-treated patients achieved a response versus 19% on placebo (P<0.0001), corresponding to a 69% placebo-adjusted response rate. How divesiran works: it silences TMPRSS6 (transmembrane serine protease 6) expressed almost exclusively in the liver; TMPRSS6 is a negative regulator of hepcidin, the body's master regulator of iron metabolism. By silencing TMPRSS6, divesiran increases hepcidin production and release by liver hepatocytes, which restricts iron availability to bone marrow and reduces the excessive red blood cell production that drives PV symptoms. Divesiran has FDA Fast Track and Orphan Drug designations for PV. Silence Therapeutics anticipates initiating a Phase 3 trial evaluating divesiran Q12W versus placebo in the first half of 2027. Shares rose sharply on the news, touching a 52-week high. The read-through extends the broader siRNA cardiometabolic and rare-disease franchise landscape that also includes Alnylam's Amvuttra and Arrowhead's Redemplo (plozasiran) in adjacent hepatic-target siRNA categories.
Protagonist Therapeutics (Nasdaq: PTGX) and Takeda are presenting four rusfertide abstracts at the 2026 European Hematology Association Congress in Stockholm (June 11-14), including analyses from the Phase 3 VERIFY study and long-term results from the Phase 2 REVIVE and THRIVE open-label extensions. The 32-week VERIFY primary analysis showed 76.9% of patients on rusfertide achieved a clinical response versus 32.9% on placebo; the 52-week dataset met the primary endpoint and all four key secondary endpoints. Rusfertide is a first-in-class subcutaneous hepcidin-mimetic peptide for polycythemia vera. The FDA accepted the rusfertide NDA in early 2026 with priority review and set a Q3 2026 PDUFA target action date.
Takeda/Protagonist Therapeutics' rusfertide, a first-in-class hepcidin mimetic peptide, received NDA acceptance and priority review. The Phase 3 VERIFY study showed it more than doubled clinical response rates.