Contributions
Abstract: EP695
Type: E-Poster Presentation
Session title: Enzymopathies, membranopathies and other anemias
Background
Hereditary spherocytosis (HS) is the most common cause of inherited red cell membranopathy, due to mutations in genes encoding membrane or cytoskeletal proteins, including band 3, ankyrin, spectrin or band 4.2. Loss of membrane cohesion results in surface area loss and generation of spherocytic red cells with decreased cellular deformability and reduced red cell survival due to splenic sequestration. A diagnostic test for HS is the incubated osmotic fragility implying a role for red cell ATP content in maintaining normal RBC function including membrane stability. Recently, relative PK deficiency has been observed in HS red cells (Andreas O et al. BJH 187: 386, 2019).
Aims
To understand whether the oral pyruvate kinase activator, mitapivat, by modulating ATP content, might have potential beneficial effects for HS RBCs in band 4.2-/- mice, a well-established model of HS (Peters LL et al JCI 103: 1527, 1999).
Methods
Mitapivat was administrated to band 4.2-/- mice at dosages of 100 mg/kg/day over 6 months. We analysed: hematologic parameters, red cell indices and osmotic fragility, markers of hemolysis, phagocytic index and iron homestasis.
Results
In band 4.2-/- mice, Mitapivat resulted in (i) decreased anemia with reduced reticulocyte count (Hb 11.6±0.035 g/dL, n=17 vs 13.104±0.09 g/dL, n=9; P<0.05; retics: 11.4±0.1%, n=16 vs 7.6±0.2%, n=7 % P<0.05) and decreased hemolytic indices (LDH, total bilirubin) with decreased spleen weight/mouse weight ratio (8.41±0.08 vs 6.53±0.06, n=8 each group; P<0.05); (ii) reduction in the proportion of phosphatidylserine positive RBCs, measured with Annexin V binding (2.4±0.02% vs 1.5±0.06% n=5-6; P<0.05); (iii) reduction of naturally occurring antibody (NAb) bound to band 4.2-/- RBC membrane; (iv) improvement of osmotic fragility. The decreased hemolysis was associated with reduction in serum erythropoietin (EPO: 1001.2±41.7 U/L vs 472 ± 12.5 U/L, n=7, P<0.05). We also documented in vivo reduction of erythrophagocytosis and in vitro decreased phagocytic index, supporting the improvement in HS red cell features by Mitapivat. The improvement of anemia in Mitapivat treated band 4.2-/- mice was associated with decreased liver iron overload.
Conclusion
Our data indicate that Mitapivat ameliorates anemia of band 4.2-/- mice, reduces chronic hemolysis and improves band 4.2-/- mouse RBC features. Thus, Mitapivat might represent a potential therapy to be explored in patients with HS.
Keyword(s): AG-348, Anemia, Mouse model, Red blood cell
Abstract: EP695
Type: E-Poster Presentation
Session title: Enzymopathies, membranopathies and other anemias
Background
Hereditary spherocytosis (HS) is the most common cause of inherited red cell membranopathy, due to mutations in genes encoding membrane or cytoskeletal proteins, including band 3, ankyrin, spectrin or band 4.2. Loss of membrane cohesion results in surface area loss and generation of spherocytic red cells with decreased cellular deformability and reduced red cell survival due to splenic sequestration. A diagnostic test for HS is the incubated osmotic fragility implying a role for red cell ATP content in maintaining normal RBC function including membrane stability. Recently, relative PK deficiency has been observed in HS red cells (Andreas O et al. BJH 187: 386, 2019).
Aims
To understand whether the oral pyruvate kinase activator, mitapivat, by modulating ATP content, might have potential beneficial effects for HS RBCs in band 4.2-/- mice, a well-established model of HS (Peters LL et al JCI 103: 1527, 1999).
Methods
Mitapivat was administrated to band 4.2-/- mice at dosages of 100 mg/kg/day over 6 months. We analysed: hematologic parameters, red cell indices and osmotic fragility, markers of hemolysis, phagocytic index and iron homestasis.
Results
In band 4.2-/- mice, Mitapivat resulted in (i) decreased anemia with reduced reticulocyte count (Hb 11.6±0.035 g/dL, n=17 vs 13.104±0.09 g/dL, n=9; P<0.05; retics: 11.4±0.1%, n=16 vs 7.6±0.2%, n=7 % P<0.05) and decreased hemolytic indices (LDH, total bilirubin) with decreased spleen weight/mouse weight ratio (8.41±0.08 vs 6.53±0.06, n=8 each group; P<0.05); (ii) reduction in the proportion of phosphatidylserine positive RBCs, measured with Annexin V binding (2.4±0.02% vs 1.5±0.06% n=5-6; P<0.05); (iii) reduction of naturally occurring antibody (NAb) bound to band 4.2-/- RBC membrane; (iv) improvement of osmotic fragility. The decreased hemolysis was associated with reduction in serum erythropoietin (EPO: 1001.2±41.7 U/L vs 472 ± 12.5 U/L, n=7, P<0.05). We also documented in vivo reduction of erythrophagocytosis and in vitro decreased phagocytic index, supporting the improvement in HS red cell features by Mitapivat. The improvement of anemia in Mitapivat treated band 4.2-/- mice was associated with decreased liver iron overload.
Conclusion
Our data indicate that Mitapivat ameliorates anemia of band 4.2-/- mice, reduces chronic hemolysis and improves band 4.2-/- mouse RBC features. Thus, Mitapivat might represent a potential therapy to be explored in patients with HS.
Keyword(s): AG-348, Anemia, Mouse model, Red blood cell