Hepcidin Peptidomimetics - Oral Efficacy in Pre-Clinical Disease Model of Iron Overload

Hepcidin peptidomimetics that are orally stable and systemically active will mark a paradigm change in management of blood disorders that exhibit aberrant iron homeostasis (e.g. hereditary hemochromatosis) and in conditions that can be influenced by modulating stressed iron homeostasis (e.g. polycythemia vera). Hepcidin modulates the iron exporter membrane protein ferroportin and is the master regulator of iron homeostasis in the body. Orally bioavailable "Minihepcidins" have been previously shown to be efficacious in lowering serum iron in mice when dosed peroral (PO) (Preza GC et. al., Journal of Clinical Investigation 2011). Here we describe hepcidin mimetic peptides that are metabolically stable in the gastrointestinal tract, systemically absorbed when delivered orally, and pharmacodynamically active in reducing serum iron parameters in pre-clinical models. Further, we also demonstrate improvement in disease parameters in a mouse model for hereditary hemochromatosis. The oral peptides, PN20076 and PN20089, have EC50 of 16.5 nM and 1.39 nM respectively in cell based ferroportin internalization assay (Table 1). In comparison EC50 was 67.8 nM for Hepcidin and 6.12 nM for PTG-300. (PTG-300 is an injectable hepcidin mimetic currently in Phase 2 clinical studies for polycythemia vera and hereditary hemochromatosis.) Oral stability of the peptides was evaluated in a panel of assays, including in vitro matrices simulating the gastric and intestinal conditions, and ex vivo matrices of serum/plasma from different species. Table 1 shows data for peptides PN20018, PN20076 and PN20089. PN20076 demonstrated extended stability in gastric and intestinal conditions, and degradation half-life of >24 hr in mouse plasma and 14.8 hr in rat serum. Based on their stability and potency data from the above battery of screening assays, the peptides were selected for in vivo evaluation in healthy mice to characterize their pharmacodynamic (PD) and pharmacokinetic (PK) properties. PN20076 and PN20089 showed equivalent PD response of reduction in serum iron concentration in wild type mice. After two successive PO doses of PN20076 or PN20089 approximately 24 hr apart, serum iron concentration was reduced from ~30 µM to ~10 µM (group averages), i.e. ~66% reduction, at 4.5 hr post-second dose for both peptides (Fig. 1). At 4.5 hr post-dose, the serum concentration of PN20076 was ~262 nM. PN20076 was further evaluated for its effect in lowering iron overload in a mouse model for hemochromatosis (HFE2-/- with homozygous deletion of hemojuvelin, a positive regulator of hepcidin expression). This mouse model is marked by hyper-absorption of dietary iron, higher transferrin saturation and deposition of excessive iron in liver, all manifestations of aberrant iron homeostasis caused by the genetic disruptions of the hepcidin-iron pathway. Liver iron accumulation was significantly prevented in groups treated with PN20076 once daily (QD) by PO administration for over two weeks, as compared to vehicle treated controls (Fig. 2). The reduction in non-heme iron concentration in liver homogenates (measured using a colorimetric iron assay) was statistically significant in the female group treated with PN20076. We have described orally stable and systemically active hepcidin mimetic peptides and demonstrated oral activity in preventing liver iron overload in hemochromatosis mice. The effective reduction of iron absorption from the diet and the steady state lowering of transferrin-saturation can potentially prevent tissue iron toxicity in hereditary hemochromatosis. Similarly, the sustained reduction of systemic iron levels with an oral hepcidin mimetic to control stressed iron homeostasis should reduce excessive erythrocytosis, a hallmark of polycythemia vera and other congenital and acquired erythropoietic disorders. Disclosures Bourne: Protagonist Therapeutics: Current Employment, Other: shareholder. Zhang:Protagonist Therapeutics: Current Employment, Other: shareholder. Frederick:Protagonist Therapeutics: Current Employment, Other: shareholder. Tran:Protagonist Therapeutics: Current Employment, Other: shareholder. Vengalam:Protagonist Therapeutics: Current Employment, Current equity holder in private company. McMahon:Protagonist Therapeutics: Current Employment, Other: shareholder. Huie:Protagonist Therapeutics: Current Employment, Other: shareholder. Ledet:Protagonist Therapeutics: Current Employment, Other: shareholder. Zhao:Protagonist Therapeutics: Current Employment, Other: shareholder. Tovera:Protagonist Therapeutics: Current Employment, Current equity holder in private company. Lee:Protagonist Therapeutics: Current Employment, Current equity holder in private company. Yang:Protagonist Therapeutics: Current Employment, Other: shareholder. Dion:Protagonist Therapeutics: Current Employment, Current equity holder in private company. Yuan:Protagonist Therapeutics: Current Employment, Other: shareholder. Zemede:Protagonist Therapeutics: Current Employment, Current equity holder in private company. Nguyen:Protagonist Therapeutics: Current Employment, Current equity holder in private company. Masjedizadeh:Protagonist Therapeutics: Current Employment, Current equity holder in private company. Cheng:Protagonist Therapeutics: Current Employment, Current equity holder in private company. Mattheakis:Protagonist Therapeutics: Current Employment, Current equity holder in private company. Liu:Protagonist Therapeutics: Current Employment, Current equity holder in private company. Smythe:Protagonist Therapeutics: Current Employment, Other: shareholder.

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Target TMPRSS6 Using Antisense Technology for the Treatment of Hereditary Hemochromatosis and β-Thalassemia

Blood ◽

10.1182/blood.v120.21.481.481 ◽

2012 ◽

Vol 120 (21) ◽

pp. 481-481 ◽

Cited By ~ 1

Author(s):

Shuling Guo ◽

Carla Casu ◽

Sara Gardenghi ◽

Sheri Booten ◽

Andy Watt ◽

...

Keyword(s):

Treatment Group ◽

Iron Overload ◽

Hereditary Hemochromatosis ◽

Iron Concentration ◽

Transferrin Saturation ◽

Control Group ◽

Mrna Levels ◽

Liver Iron ◽

Hepcidin Expression ◽

Antisense Technology

Abstract Abstract 481 Hepcidin, the master regulator of iron homeostasis, is a peptide that is mainly expressed and secreted by the liver. Low levels of hepcidin are associated with increased iron absorption. In conditions in which hepcidin is chronically repressed, such as hereditary hemochromatosis and b-thalassemia, patients suffer from iron overload and very severe pathophysiological sequelae associated with this condition. Hepcidin expression is regulated predominantly at the transcriptional level by multiple factors. TMPRSS6, a transmembrane serine protease mutated in iron-refractory, iron-deficient anemia, is a major suppressor of hepcidin expression. It has been demonstrated that hepcidin expression is significantly elevated in Tmprss6−/− mice and reduction of Tmprss6 expression in hereditary hemochromatosis (Hfe−/−) mice ameliorates the iron overload phenotype (Finberg et al. Nature Genetics, 2008; Du et al. Science 2008; Folgueras et al. Blood 2008; Finberg et al., Blood, 2011). It has also been demonstrated that hepcidin up-regulation using either a hepcidin transgene or Tmprss6−/− significantly improves iron overload and anemia in a mouse model of β-thalassemia intermedia (th3/+ mice) (Gardenghi et al. JCI, 120:4466, 2010; Nai et al. Blood, 119: 5021, 2012). In this report, we have examined whether reduction of Tmprss6 expression using antisense technology is an effective approach for the treatment of hereditary hemochromatosis and β-thalassemia. Second generation antisense oligonucleotides (ASOs) targeting mouse Tmprss6 were identified. When normal male C57BL/6 mice were treated with 25, 50 and 100mg/kg/week ASO for four weeks, we achieved up to >90% reduction of liver Tmprss6 mRNA levels and up to 5-fold induction of hepcidin mRNA levels in a dose-dependent manner. Dose-dependent reductions of serum iron and transferrin saturation were also observed. ASOs were well tolerated in these animals. In Hfe−/− mice (both males and females), ASOs were administrated at 100 mg/kg for six weeks. This treatment normalized transferrin saturation (from 92% in control animals to 26% in treatment group) and significantly reduced serum iron (from >300ug/dl in control group to <150ug/dl in treatment group), as well as liver iron accumulation. Histopathological evaluation and Prussian's Perl Blue staining indicated that iron was sequestered by macrophages, which led to an increase in spleen iron concentration. The mouse model of thalassemia intermedia that we utilized mimics a condition defined as non-transfusion dependent thalassemia (NTDT) in humans. These patients exhibit increased iron absorption and iron overload due to ineffective erythropoiesis and suppression of hepcidin; iron overload is the most frequent cause of morbidity and mortality. Th3/+ animals exhibit ineffective erythropoiesis, characterized by increased proliferation and decreased differentiation of the erythroid progenitors, apoptosis of erythroblasts due to the presence of toxic hemichromes, reticulocytosis and shorter lifespan of red cells in circulation, leading to splenomegaly, extramedullary hematopoiesis and anemia (∼ 8 g/dL; Libani et al, Blood 112(3):875–85, 2008). Five month old th3/+ mice (both males and females) were treated with Tmprss6 ASO for six weeks. In th3/+ mice, ∼85% Tmprss6 reduction led to dramatic reductions of serum transferrin saturation (from 55–63% in control group down to 20–26% in treatment group). Liver iron concentration (LIC) was also greatly reduced (40–50%). Moreover, anemia endpoints were significantly improved with ASO treatment, including increases in red blood cells (∼30–40%), hemoglobin (∼2 g/dl), and hematocrit (∼20%); reduction of splenomegaly (∼50%); decrease of serum erythropoietin levels (∼50%); improved erythroid maturation as indicated by a strong reduction in reticulocyte number (50–70%) and in a normalized proportion between the pool of erythroblasts and enucleated erythroid cells. Hemichrome analysis showed a significant decrease in the formation of toxic alpha-globin/heme aggregates associated with the red cell membrane. This was consistent with a remarkable improvement of the red cell distribution width (RDW) as well as morphology of the erythrocytes. In conclusion, these data demonstrate that targeting TMPRSS6 using antisense technology is a promising novel therapy for the treatment of hereditary hemochromatosis and β-thalassemia. Disclosures: Guo: Isis Pharmaceuticals: Employment. Booten:Isis Pharmaceuticals: Employment. Watt:Isis Pharmaceuticals: Employment. Freier:Isis Pharmaceuticals: Employment. Rivella:Novartis Pharmaceuticals: Consultancy; Biomarin: Consultancy; Merganser Biotech: Consultancy, Equity Ownership, Research Funding; Isis Pharma: Consultancy, Research Funding. Monia:Isis Pharmaceuticals: Employment.

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Liver Iron Concentration Measurements Using MRI R2 in MDS Patients in a Deferasirox (Exjade®, ICL670) Phase II Study.

Blood ◽

10.1182/blood.v108.11.4846.4846 ◽

2006 ◽

Vol 108 (11) ◽

pp. 4846-4846 ◽

Cited By ~ 1

Author(s):

Peter L. Greenberg ◽

Charles A. Schiffer ◽

Charles Asa Koller ◽

Barinder Kang ◽

Jodie Decker ◽

...

Keyword(s):

Iron Overload ◽

Serum Ferritin ◽

Serum Iron ◽

Iron Concentration ◽

Transferrin Saturation ◽

Ongoing Study ◽

Liver Iron Concentration ◽

Liver Iron ◽

Calculated Creatinine Clearance ◽

L 14

Abstract Introduction: Approximately 60% of patients with myelodysplastic syndromes (MDS) require ongoing red blood cell transfusions, which can lead to significant iron overload and associated morbidities. Historically, many of these patients have not received iron chelation therapy due to burdensome administration of deferoxamine. Deferasirox (Exjade®, ICL670) is a once-daily, oral iron chelator recently approved for the treatment of chronic iron overload due to blood transfusions. This ongoing study is designed to evaluate the efficacy and safety of deferasirox in Low/Int-1-risk MDS patients. In addition, this is the first prospective, multicenter trial to evaluate liver iron concentration (LIC) using the MRI R2 parameter in this population. Methods: This ongoing study will enroll 30 patients at three US centers. Deferasirox will be administered at 20–30 mg/kg/day for 12 months. Iron burden is being monitored by monthly serum ferritin evaluations, and LIC by MRI R2 at baseline, 6 and 12 months. Serum iron, transferrin, transferrin saturation, labile plasma iron (LPI), and urinary hepcidin are being assessed throughout the study. In addition, serum creatinine, calculated creatinine clearance, echocardiograms and hematological status are being monitored. In this report, we are presenting the baseline data for the currently enrolled patients. Results: As of May 2006, 14 patients (9 male, 5 female; aged 55–81 years) were enrolled. All patients were Caucasian with equal distribution of Low- and Int-1-risk MDS. The mean interval from MDS diagnosis to screening was 4 years, ranging from <1 to 12 years. The table summarizes baseline iron parameters in these patients: Parameter n Mean ± SD Median Range Normal range n/a, not applicable LIC, mg Fe/g dw 14 21.8 ± 11.0 23.5 3.8–40.5 <1.3 Serum ferritin,μg/L 14 4645 ± 3804 3534.5 1433–15380 20–360 Serum iron, μg/dL 14 205.9 ± 26.5 200 165.9–252.0 50–160 Transferrin, mg/dL 14 143 ± 19 142.5 106–172 200–400 Transferrin saturation, % 14 113.8 ± 8.5 114 95–124 15–50 LPI, μmol/L 14 0.7 ± 0.7 0.6 0–1.9 0 Num. of lifetime transfusions 14 106.3 ± 115.5 47.5 30–352 n/a Renal function: Calculated creatinine clearance at baseline was normal (>80 mL/min) in 46% of patients, mildly impaired (50–80 mL/min) in 46% and moderately impaired (30–50 mL/min) in 8% of patients. Hematological parameters: neutropenia (<1800/μL): 1 patient; thrombocytopenia (<100,000/μL): 3 patients; neutropenia and thrombocytopenia: 1 patient. Concurrent therapies: Revlimid: 2 patients; and hydroxyurea: 1 patient. Conclusions: Baseline iron burden in these patients demonstrates a high degree of iron overload, as measured by LIC via MRI, as well as serum ferritin, serum iron and transferrin saturation. Based on NCCN guidelines for the management of iron overload, the degree of iron overload observed meets criteria for treatment. This ongoing study is assessing the safety and efficacy of deferasirox in this population.

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A High Through-Put Screen Identifies MCP-1 (CCL2) As a Novel Regulator of Iron Homeostasis and a Modifier of Hereditary Hemochromatosis Disease Severity

Blood ◽

10.1182/blood.v118.21.685.685 ◽

2011 ◽

Vol 118 (21) ◽

pp. 685-685

Author(s):

Martina U. Muckenthaler ◽

Maja Vujic Spasic ◽

Katarzyna Mleczko-Sanecka ◽

Mingang Zhu ◽

Rainer Pepperkok ◽

...

Keyword(s):

Iron Overload ◽

Mrna Expression ◽

Disease Severity ◽

Iron Homeostasis ◽

Expression Profiles ◽

Hereditary Hemochromatosis ◽

Transferrin Saturation ◽

Human Cells ◽

Liver Iron ◽

Deficient Mice

Abstract Abstract 685 To identify genes that modify the severity of human iron disorders we pre-selected 74 genes from gene expression profiles of cells and tissues with altered iron levels and assessed whether siRNA-mediated knock-down of these genes affects uptake of transferrin, a key cellular process to acquire iron. This screen identifies the monocyte chemoattractant protein-1 (MCP-1), also known as CCL2, as a critical suppressor of transferrin receptor mRNA expression in human cells. We next analyzed CCL2-deficient mice and demonstrate profound alterations of parameters of systemic iron homeostasis. Specifically, CCL2 knock-out mice show decreased serum iron levels and transferrin saturation, strong iron-overload in the spleen and duodenum as well as mild iron accumulation in the liver. Iron imbalance in CCL2−/− mice is unlikely explained by an impairment of the major control system of systemic iron homeostasis, the hepcidin/ferroportin regulatory system: hepcidin mRNA expression is unaltered and splenic ferroportin protein expression is strongly increased in CCL2−/− mice, as would be expected as a consequence of splenic iron overload. We speculate that increased iron absorption from the plasma, possibly mediated by inappropriately high levels of TfR1 in the spleen, duodenum and liver, may be responsible for tissue iron overload. It is of note that CCL2 levels are strongly decreased in Hfe-deficient mice and patients with Hfe-associated Hereditary Hemochromatosis (HH). We therefore asked whether CCL2 levels could modify disease severity of HH. Analysis of 51 HH patients, all homozygous for the C282Y HFE mutation, confirms significantly lower MCP-1 levels in the serum compared to a group of 23 sex- and age-matched normal controls. Importantly, CCL2 levels in HH patients show a significant negative correlation with liver iron overload at the time point of diagnosis. Furthermore, low CCL2 concentrations are significantly associated with the HLA-A3 genotype and the CD8+ T lymphocyte phenotype, both traits previously shown to correlate with iron overload in HH patients. These patient data and the data from CCL2-deficient mice suggest that appropriate CCL2 expression is required to prevent iron overload. Taken together our data demonstrate the power of siRNA screens to identify novel regulators of iron metabolism in human cells that are critically involved in maintaining systemic iron homeostasis in the mouse and that play a role in modifying hepatic iron overload in the frequent iron overload disorder Hereditary Hemochromatosis. Disclosures: No relevant conflicts of interest to declare.

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The Effect of the Flavonol Rutin on Serum and Liver Iron Content in a Genetic Mouse Model of Iron Overload

Bioscience Reports ◽

10.1042/bsr20210720 ◽

2021 ◽

Author(s):

Zachary Hawula ◽

Eriza Secondes ◽

Daniel Wallace ◽

Gautam Rishi ◽

V. Nathan Subramaniam

Keyword(s):

Mouse Model ◽

Iron Overload ◽

Transferrin Receptor ◽

Iron Homeostasis ◽

Binding Capacity ◽

Hereditary Hemochromatosis ◽

Transferrin Saturation ◽

Iron Loading ◽

Genetic Mouse Model ◽

Transferrin Receptor 2

The flavonol rutin has been shown to possess antioxidant and iron chelating properties in vitro and in vivo. These dual properties are beneficial as therapeutic options to reduce iron accumulation and the generation of reactive oxygen species resultant from excess free iron. The effect of rutin on iron metabolism has been limited to studies performed in wild type mice either injected or fed high iron diets. The effect of rutin on iron overload caused by genetic dysregulation of iron homeostasis has not yet been investigated. In this study we examined the effect of rutin treatment on tissue iron loading in a genetic mouse model of iron overload, which mirrors the iron loading associated with Type 3 hereditary hemochromatosis patients who have a defect in Transferrin Receptor 2. Male Transferrin Receptor 2 knockout mice were administered rutin via oral gavage for 21 continuous days. Following treatment, iron levels in serum, liver, duodenum, and spleen were assessed. In addition, hepatic ferritin protein levels were determined by western blotting, and expression of iron homeostasis genes by quantitative real-time PCR. Rutin treatment resulted in a significant reduction in hepatic ferritin protein expression and serum transferrin saturation. In addition, trends towards decreased iron levels in the liver and serum, and increased serum unsaturated iron binding capacity were observed. This is the first study to explore the utility of rutin as a potential iron chelator and therapeutic in an animal model of genetic iron overload.

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Rusfertide (PTG-300), a Hepcidin Mimetic, Maintains Liver Iron Concentration in the Absence of Phlebotomies in Patients with Hereditary Hemochromatosis

Blood ◽

10.1182/blood-2021-149197 ◽

2021 ◽

Vol 138 (Supplement 1) ◽

pp. 943-943

Author(s):

Kris V Kowdley ◽

Nishit B Modi ◽

Frank Valone ◽

Victor M. Priego ◽

Christopher Ferris ◽

...

Keyword(s):

Adverse Events ◽

Serum Iron ◽

Clinical Laboratory ◽

Hematological Parameters ◽

Hereditary Hemochromatosis ◽

Iron Concentration ◽

Transferrin Saturation ◽

Liver Iron Concentration ◽

Open Label ◽

Liver Iron

Abstract Introduction: Patients with hereditary hemochromatosis (HH) require continued phlebotomies to limit end-organ damage. Approximately 25% of patients in maintenance felt receiving phlebotomies was "inconvenient" or "very inconvenient" (Brisott et al, 2011). Patient compliance with phlebotomies generally declines with time (Hicken et al, 2003), and therapeutic phlebotomies may not be medically suitable for some HH patients. Rusfertide, a peptide mimetic of hepcidin, is an effective regulator of iron distribution and utilization that has demonstrated control of iron in an animal model of HH. Methods: We conducted an open-label, dose-finding efficacy study that investigated subcutaneous rusfertide in HH patients on a stable phlebotomy regimen of 0.25 to 1 phlebotomy per month for at least 6 months. Patients with clinical laboratory abnormalities and those receiving iron chelation therapy or erythrocytapheresis were excluded. Subjects received individually titrated rusfertide doses once or twice a week to maintain transferrin saturation (TSAT) below 45% and were followed for 6 months. Study measures included TSAT, serum iron, transferrin and ferritin, liver iron concentration (LIC) measured by MRI, and adverse events (AEs). Results: Sixteen subjects (10 male/6 female) were enrolled. Mean age and weight were 62.5 years and 88.1 kg, respectively. LIC values were maintained at pre-study levels, with minimal use of phlebotomies during the duration of the study (Figure 1A). Average pre-study phlebotomy rate was 0.27 phlebotomies/month compared to 0.03 phlebotomies/month during the study (p<0.0001; Figure 1B). There was a dose- and concentration-dependent decrease in serum iron and TSAT (Figure 2A and 2B). Transferrin levels were relatively constant over the course of the study. There were no notable changes in hematological parameters such as hematocrit, erythrocytes, leucocytes, or platelets. Rusfertide was generally well tolerated. Adverse events reported in 2 or more subjects included diarrhea, fatigue, injection site reactions (erythema, induration, pain, pruritis), dizziness, and headache. Conclusions: Rusfertide demonstrated a pharmacodynamic effect in reducing TSAT and serum iron, with corresponding significant reduction in the number of phlebotomies, and with LIC maintained at pre-study levels with minimal use of phlebotomies. These data indicate rusfertide was well tolerated in patients with HH and controls LIC, supporting development of rusfertide as a potential treatment for HH. Figure 1 Figure 1. Disclosures Kowdley: PTG: Consultancy, Research Funding. Modi: Protagonist Therapeutics: Current Employment. Valone: Protagonist Therapeutics: Current Employment, Current equity holder in publicly-traded company. Gupta: Protagonist Therapeutics: Current Employment.

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The Oral Ferroportin Inhibitor VIT-2763 Improves Erythropoiesis without Interfering with Iron Chelation Therapy in a Mouse Model of β-Thalassemia

International Journal of Molecular Sciences ◽

10.3390/ijms22020873 ◽

2021 ◽

Vol 22 (2) ◽

pp. 873

Author(s):

Naja Nyffenegger ◽

Anna Flace ◽

Cédric Doucerain ◽

Franz Dürrenberger ◽

Vania Manolova

Keyword(s):

Mouse Model ◽

Iron Overload ◽

Chelation Therapy ◽

Iron Concentration ◽

Transferrin Saturation ◽

Iron Chelation ◽

Iron Chelator ◽

Liver Iron Concentration ◽

Ineffective Erythropoiesis ◽

Liver Iron

In β-thalassemia, ineffective erythropoiesis leads to anemia and systemic iron overload. The management of iron overload by chelation therapy is a standard of care. However, iron chelation does not improve the ineffective erythropoiesis. We recently showed that the oral ferroportin inhibitor VIT-2763 ameliorates anemia and erythropoiesis in the Hbbth3/+ mouse model of β-thalassemia. In this study, we investigated whether concurrent use of the iron chelator deferasirox (DFX) and the ferroportin inhibitor VIT-2763 causes any pharmacodynamic interactions in the Hbbth3/+ mouse model of β-thalassemia. Mice were treated with VIT-2763 or DFX alone or with the combination of both drugs once daily for three weeks. VIT-2763 alone or in combination with DFX improved anemia and erythropoiesis. VIT-2763 alone decreased serum iron and transferrin saturation (TSAT) but was not able to reduce the liver iron concentration. While DFX alone had no effect on TSAT and erythropoiesis, it significantly reduced the liver iron concentration alone and in the presence of VIT-2763. Our results clearly show that VIT-2763 does not interfere with the iron chelation efficacy of DFX. Furthermore, VIT-2763 retains its beneficial effects on improving ineffective erythropoiesis when combined with DFX in the Hbbth3/+ mouse model. In conclusion, co-administration of the oral ferroportin inhibitor VIT-2763 and the iron chelator DFX is feasible and might offer an opportunity to improve both ineffective erythropoiesis and iron overload in β-thalassemia.

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Comparison of 3 Tfr2-deficient murine models suggests distinct functions for Tfr2-α and Tfr2-β isoforms in different tissues

Blood ◽

10.1182/blood-2009-09-240960 ◽

2010 ◽

Vol 115 (16) ◽

pp. 3382-3389 ◽

Cited By ~ 43

Author(s):

Antonella Roetto ◽

Ferdinando Di Cunto ◽

Rosa Maria Pellegrino ◽

Emilio Hirsch ◽

Ornella Azzolino ◽

...

Keyword(s):

Iron Overload ◽

Transcriptional Control ◽

Iron Homeostasis ◽

Transmembrane Protein ◽

Iron Concentration ◽

Transferrin Saturation ◽

Liver Iron ◽

Liver Iron Overload ◽

Diferric Transferrin ◽

Main Regulator

Abstract Transferrin receptor 2 (TFR2) is a transmembrane protein that is mutated in hemochromatosis type 3. The TFR2 gene is transcribed in 2 main isoforms: the full-length (α) and a shorter form (β). α-Tfr2 is the sensor of diferric transferrin, implicated in the modulation of hepcidin, the main regulator of iron homeostasis. The function of the putative β-Tfr2 protein is unknown. We have developed a new mouse model (KI) lacking β-Tfr2 compared with Tfr2 knockout mice (KO). Adult Tfr2 KO mice show liver iron overload and inadequate hepcidin levels relative to body iron stores, even though they increase Bmp6 production. KI mice have normal transferrin saturation, liver iron concentration, hepcidin and Bmp6 levels but show a transient anemia at young age and severe spleen iron accumulation in adult animals. Fpn1 is strikingly decreased in the spleen of these animals. These findings and the expression of β-Tfr2 in wild-type mice spleen suggest a role for β-Tfr2 in Fpn1 transcriptional control. Selective inactivation of liver α-Tfr2 in KI mice (LCKO-KI) returned the phenotype to liver iron overload. Our results strengthen the function of hepatic α-Tfr2 in hepcidin activation, suggest a role for extrahepatic Tfr2 and indicate that β-Tfr2 may specifically control spleen iron efflux.

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Comparing the Value of Serum Ferritin, Transfusion History and Magnetic Resonance Imaging for the Prediction of Iron Overload In MDS and AML Patients Undergoing Allogeneic Stem Cell Transplantation.

Blood ◽

10.1182/blood.v116.21.3493.3493 ◽

2010 ◽

Vol 116 (21) ◽

pp. 3493-3493

Author(s):

Martin Wermke ◽

Jan Moritz Middeke ◽

Nona Shayegi ◽

Verena Plodeck ◽

Michael Laniado ◽

...

Keyword(s):

Iron Overload ◽

Serum Ferritin ◽

Iron Content ◽

Iron Concentration ◽

Transferrin Saturation ◽

Resonance Imaging ◽

Liver Iron Concentration ◽

Liver Iron ◽

Liver Iron Content ◽

Transfusion History

Abstract Abstract 3493 An increased risk for GvHD, infections and liver toxicity after transplant has been attributed to iron overload (defined by serum ferritin) of MDS and AML patients prior to allogeneic hematopoietic stem cell transplantation (allo-HSCT). Nevertheless, the reason for this observation is not very well defined. Consequently, there is a debate whether to use iron chelators in these patients prior to allo-HSCT. In fact, serum ferritin levels and transfusion history are commonly used to guide iron depletion strategies. Both parameters may inadequately reflect body iron stores in MDS and AML patients prior to allo-HSCT. Recently, quantitative magnetic resonance imaging (MRI) was introduced as a tool for direct measurement of liver iron. We therefore aimed at evaluating the accurateness of different strategies for determining iron overload in MDS and AML patients prior to allo-HSCT. Serologic parameters of iron overload (ferritin, iron, transferrin, transferrin saturation, soluble transferrin receptor) and transfusion history were obtained prospectively in MDS or AML patients prior to allo-SCT. In parallel, liver iron content was measured by MRI according to the method described by Gandon (Lancet 2004) and Rose (Eur J Haematol 2006), respectively. A total of 20 AML and 9 MDS patients (median age 59 years, range: 23–74 years) undergoing allo-HSCT have been evaluated so far. The median ferritin concentration was 2237 μg/l (range 572–6594 μg/l) and patients had received a median of 20 transfusions (range 6–127) before transplantation. Serum ferritin was not significantly correlated with transfusion burden (t = 0.207, p = 0.119) but as expected with the concentration of C-reactive protein (t = 0.385, p = 0.003). Median liver iron concentration measured by MRI was 150 μmol/g (range 40–300 μmol/g, normal: < 36 μmol/g). A weak but significant correlation was found between liver iron concentration and ferritin (t = 0.354; p = 0.008). The strength of the correlation was diminished by the influence of 5 outliers with high ferritin concentrations but rather low liver iron content (Figure 1). The same applied to transfusion history which was also only weakly associated with liver iron content (t = 0.365; p = 0.007). Levels of transferrin, transferrin saturation, total iron and soluble transferrin receptor did not predict for liver iron concentration. Our data suggest that serum ferritin or transfusion history cannot be regarded as robust surrogates for the actual iron overload in MDS or AML patients. Therefore we advocate caution when using one of these parameters as the only trigger for chelation therapy or as a risk-factor to predict outcome after allo-HSCT. Figure 1. Correlation of Liver iron content with Ferritin. Figure 1. Correlation of Liver iron content with Ferritin. Disclosures: No relevant conflicts of interest to declare.

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RNAi-Mediated Inhibition of Tmprss6 Elevates Hamp1 Expression and Reduces Serum Iron Levels in Mice

Blood ◽

10.1182/blood.v118.21.1045.1045 ◽

2011 ◽

Vol 118 (21) ◽

pp. 1045-1045 ◽

Cited By ~ 1

Author(s):

Ivanka Toudjarska ◽

Zuhua Cai ◽

Tim Racie ◽

Stuart Milstein ◽

Brian R Bettencourt ◽

...

Keyword(s):

Iron Overload ◽

Serum Iron ◽

Iron Concentration ◽

Transferrin Saturation ◽

Elevated Serum ◽

High Serum ◽

Therapeutic Modality ◽

Deficiency Anemia ◽

Loss Of Function ◽

Hepcidin Expression

Abstract Abstract 1045 The liver hormone Hepcidin (encoded by Hamp1) regulates serum iron levels by controlling the efflux of iron from intestinal enterocytes and macrophages. Maintaining sufficient iron levels to support erythropoiesis while preventing iron overload requires tight control of Hepcidin expression. Transcription of Hamp1 in hepatocytes is stimulated by high serum iron levels, via Transferrin Receptor signaling, as well as by activation of the BMP/SMAD pathway. The membrane serine protease Matriptase-2 (encoded by Tmprss6) inhibits BMP induced Hamp1 induction through the regulation of the BMP co-receptor, Hemojuvelin. In humans, loss of function mutations in TMPRSS6 lead to elevated Hepcidin levels resulting in iron-resistant iron-deficiency anemia (IRIDA). In diseases associated with iron overload, such as Thalassemia intermedia (TI) and Familial Hemochromatosis (FH), Hepcidin levels are low despite elevated serum iron concentrations. Studies in murine models of TI and FH have shown that elevating Hepcidin levels by genetic inactivation of Tmprss6 can prevent iron overload and correct aspects of the disease phenotype. Therefore, therapeutic strategies aimed at specifically inhibiting Tmprss6 expression could prove efficacious in these, and other, iron overloading diseases. Here we show that systemic administration of a potent lipid nanoparticle (LNP) formulated siRNA directed against Tmprss6 leads to durable inhibition of Tmprss6 mRNA in the mouse liver, with concomitant elevation of Hamp1 expression. This leads to significant decreases in serum iron concentration and Transferrin saturation, along with changes in hematologic parameters consistent with iron restriction. Further testing in mouse genetic models of TI and FH will support the rationale for developing LNP formulated Tmprss6 siRNA as a novel therapeutic modality. Disclosures: Toudjarska: Alnylam Pharmaceuticals, Inc.: Employment. Cai:Alnylam Pharmaceuticals, Inc.: Employment. Racie:Alnylam Pharmaceuticals, Inc.: Employment. Milstein:Alnylam Pharmaceuticals, Inc.: Employment. Bettencourt:Alnylam Pharmaceuticals, Inc.: Employment. Hettinger:Alnylam Pharmaceuticals, Inc.: Employment. Sah:Alnylam Pharmaceuticals, Inc.: Employment. Vaishnaw:Alnylam Pharmaceuticals, Inc.: Employment. Bumcrot:Alnylam Pharmaceuticals, Inc.: Employment.

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Targeting TMPRSS6 Using Antisense Technology for the Treatment of Beta-Thalassemia

Blood ◽

10.1182/blood.v126.23.753.753 ◽

2015 ◽

Vol 126 (23) ◽

pp. 753-753 ◽

Cited By ~ 2

Author(s):

Shuling Guo ◽

Mariam Aghajan ◽

Carla Casu ◽

Sara Gardenghi ◽

Sheri Booten ◽

...

Keyword(s):

Mouse Model ◽

Targeted Delivery ◽

Serum Iron ◽

Iron Concentration ◽

Transferrin Saturation ◽

Beta Thalassemia ◽

Control Group ◽

Mrna Levels ◽

Antisense Technology ◽

Wide Range

Abstract Antisense technology is a powerful drug discovery approach for identifying oligonucleotide analogs that can specifically modify RNA expression through multiple mechanisms including RNase H-mediated degradation of RNA and modulation of RNA splicing. We have successfully applied this technology towards targeting a number of transcripts in a wide-range of therapeutic areas. Beta-thalassemia, one of the most common genetic disorders worldwide, is characterized by reductions in beta-globin and ineffective erythropoiesis. This in turn leads to suppression of hepcidin, a peptide hormone that serves as the master regulator of iron homeostasis. Inappropriately low levels of hepcidin trigger increased dietary iron absorption resulting in iron overload, which is the major cause of morbidity and mortality in beta-thalassemia patients. TMPRSS6 is a transmembrane serine protease mainly produced by hepatocytes that negatively regulates hepcidin expression. Previous mouse and human genetic data from multiple groups suggest that lowering TMPRSS6 expression could up-regulate hepcidin and ameliorate many of the disease symptoms associated with β-thalassemia. We identified potent antisense oligonucleotides (ASOs) against mouse TMPRSS6. Downregulation of TMPRSS6 with ASO treatment resulted in dose-dependent hepcidin upregulation and reduction in serum iron and transferrin saturation in normal mice. In a mouse model of beta-thalassemia (th3/+ mice), which effectively recapitulates beta-thalassemia intermedia in humans, TMPRSS6 reduction resulted in induction of hepcidin and dramatic reductions of serum transferrin saturation (from 55-63% in control group down to 20-26% in treatment group). Liver iron concentration (LIC) was also greatly reduced (40-50%). Moreover, anemia endpoints were significantly improved with ASO treatment, including increases in red blood cells (~30-40%), hemoglobin (~2 g/dl), and hematocrit (~20%); reduction of splenomegaly; decreases in serum erythropoietin levels; improved erythroid maturation as indicated by a strong reduction in reticulocyte number and a normalized proportion between the pool of erythroblasts and enucleated erythroid cells. Encouraged by the strong pharmacology of TMPRSS6 suppression in animal models, we initiated an effort to identify a human TMPRSS6 clinical candidate with a liver-targeted delivery strategy. Over 2000 ASOs were screened in cell lines and the most active compounds were evaluated in rodent tolerability studies. A human TMPRSS6 transgenic mouse model was established enabling evaluation of ASO activity toward human TMPRSS6 transcript in vivo. Furthermore, lead compounds were tested in a 3-month study in normal monkeys. With repeated dosing, TMPRSS6 mRNA levels in monkey liver were reduced by >90%, accompanied by time-dependent reductions of serum iron (from ~100-120ug/dl to <40ug/dl), transferrin saturation (from ~30-35% to <10%), and hemoglobin. These compounds were well tolerated in rodents and in monkeys. Collectively, our data demonstrate that TMPRSS6 ASO could be an effective therapeutic for patients with beta-thalassemia and related disorders. A Phase 1 clinical trial is planned to initiate in 2016. Disclosures Guo: Isis Pharmaceuticals: Employment, Other: Shareholder. Aghajan:Isis Pharmaceuticals: Employment, Other: Shareholder. Booten:Isis Pharmaceuticals: Employment, Other: Shareholder. Monia:Isis Pharmaceuticals: Employment, Other: Shareholder.

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