Regulation of Iron Homeostasis and Efficacy of Rusfertide Analog Peptide in a Mouse Model for Polycythemia Vera

• Published in: Blood 2021-11, Vol.138 (Supplement 1), p.2006-2006
• Main Authors: Taranath, Roopa, Zhao, Li, Vengalam, Jayanthi, Lee, Lawrence, Tang, Tenny, Dion, Celino, Su, Ahu, Tovera, James, Bhandari, Ashok, Cheng, Xiaoli, Mattheakis, Larry, Liu, David Y
• Format: Article
• Language: English
• ISSN: 0006-4971; 1528-0020
• DOI: 10.1182/blood-2021-154118

Polycythemia Vera (PV) is a rare blood disease where mutations in JAK2 kinase confer constitutive JAK2 activity leading to abnormally elevated erythropoiesis that is independent of erythropoietin. PV patients present with iron deficiency at diagnosis due to increased iron utilization for erythropoiesis (Ginzburg YZ, Leukemia 2018) which worsens after repeated therapeutic phlebotomy (TP) performed to maintain hematocrit below 45%. The resulting suppression of hepcidin, the body's main negative regulator of iron metabolism, fuels expanded erythropoiesis resulting in a continued need for TP and thereby exacerbating patients' iron deficiency. Rusfertide targets iron exporter membrane protein ferroportin to trigger its degradation, preventing iron export from cells responsible for dietary iron absorption and cells that store and recycle iron. The resulting pharmacodynamic effect of lowered serum iron has disease-modifying effects in PV (Ginzburg YZ, Leukemia 2018). Rusfertide essentially eliminated the need for therapeutic phlebotomy in all PV patients (Kremyanskaya M, Blood 2020 136 Suppl 1: 33). Rusfertide also reversed iron deficiency, as indicated by increased serum ferritin, mean corpuscular volume (MCV), and mean corpuscular hemoglobin (MCH) in these patients. We present results from studies in a mouse PV model with JAK2-V617F mutation as in human PV (Mullaly A, Cancer Cell 2010; JAX stock #031658). We show that rusfertide analog Peptide A is efficacious in lowering hematocrit (HCT) while modulating other hematological parameters. Further, we show redistribution of iron away from erythropoiesis and renormalization of iron homeostasis as evidenced by ferrokinetic parameters. PV mice were treated over 6-weeks (thrice per week) with Vehicle or Peptide A at 2.5 or 7.5 mg/kg. At the end of 6 weeks, hematology parameters HCT, hemoglobin, RBC counts, were elevated in the PV-Vehicle group as compared to wild type (WT-Vehicle) mice (Table 1). Hematology parameters in PV-2.5 mg/kg group were lowered to WT-Vehicle values. In PV-7.5 mg/kg group, these parameters were lower than WT-Vehicle values, indicating that excessive iron restriction (EIR) leads to the expected anemic conditions. MCH and mean corpuscular hemoglobin concentration (MCHC) in PV-Vehicle group and PV-2.5 mg/kg treated were comparable to WT-Vehicle, indicating a lack of EIR. For the PV-7.5 mg/kg treated group, MCH and MCHC were significantly lower than WT-Vehicle, suggesting EIR at a high dose impacts