Contributions
Abstract: EP758
Type: E-Poster Presentation
Session title: Hematopoiesis, stem cells and microenvironment
Background
Erythropoiesis, the multi-stage differentiation process of hematopoietic stem cells to red blood cells (RBCs), is a tightly regulated process required for adequate blood supply. Ineffective erythropoiesis causing anemia, such as in myelodysplastic syndromes (MDS) or myelofibrosis (MF), can result from defects at any stage in the pathway. However, current treatments target distinct stages of erythropoiesis, resulting in some patients being unresponsive to treatment; targeting multiple stages of erythropoiesis may provide a better treatment option.
The TGF-β superfamily regulates erythropoiesis by maintaining a balance between progenitor quiescence and differentiation. KER-050, a modified ActRIIA ligand trap, is designed to promote erythropoiesis through inhibition of TGF-β ligands that signal though SMAD2/3, including activins and GDFs. In a Phase 1 clinical study, administration of KER-050 to healthy volunteers led to a robust, rapid, and sustained increase in RBCs and hemoglobin (HGB) as well as an increase in platelets, potentially suggesting a broader effect of KER-050 on hematopoiesis.
Aims
Determine the durability of effect and mechanism of action of KER-050 on erythropoiesis.
Methods
C57BL/6 male mice (12-week-old) were treated with a single dose of either vehicle or a research form of KER-050 (RKER-050). Peripheral blood was evaluated for reticulocytes (RET), RBCs, and HGB, and bone marrow (BM) erythroblasts were analyzed by flow cytometry, at multiple time points from 12 hours (hr) through day 51. Erythropoietin (Epo) levels were measured in serum.
Results
Treatment with RKER-050 resulted in rapid and sustained increases in RBCs and HGB, observed from 12hr through day 51. Within 12hr, RBCs (+8%) and HGB (+9%) were significantly increased. This response corresponded to a 20% reduction in BM proerythroblasts and erythroblasts (TER119+ cells) and a concomitant 18% increase (compared to vehicle) in circulating RETs, supporting that the maturation of these late-stage precursors contributed to the rapid RBC effect. Indeed, analysis of specific BM populations showed a general shift in the TER119+ cells from early to late erythroblast populations.
Within 48hr, the number of BM TER119+ cells increased by 37% compared to vehicle, demonstrating that precursor pools reduced at 12hr were quickly restored. In parallel, the initial increase in RETs observed at 12hr were transiently reduced (-15%), implying continued late-stage maturation of RETs to RBCs. This continued movement of earlier stage erythroid precursors into later stages of the pathway continued, with RET levels again replenished and TER119+ cells reduced by 48hr, likely supporting that the robust and sustained response in RBCs was due to administration of KER-050.
In addition to RKER-050 promoting differentiation of erythroid precursors to elicit its effect on RBCs, a RKER-050-mediated upregulation of Epo may also be contributing to the sustained increase in RBCs. Epo does not appear to play a role in the initial rapid RBC increase since Epo upregulation was not observed until day 4; however, Epo was increased from day 4 through day 37 which could indicate a role in sustaining the RKER-050-mediated increase in RET (+4%), RBCs (+8%), and HGB (+3%) to at least day 51.
Conclusion
In these studies, we observed that RKER-050 had a rapid and durable effect on erythropoiesis. The observed effects of RKER-050 on multiple stages of erythroblast maturation (both early- and late-stage) and increase in circulating EPO provide a strong rationale for investigating KER-050 as a treatment for ineffective hematopoiesis in MDS and MF.
Keyword(s): Erythropoieisis, MDS, Myelofibrosis, Transforming growth factor-
Abstract: EP758
Type: E-Poster Presentation
Session title: Hematopoiesis, stem cells and microenvironment
Background
Erythropoiesis, the multi-stage differentiation process of hematopoietic stem cells to red blood cells (RBCs), is a tightly regulated process required for adequate blood supply. Ineffective erythropoiesis causing anemia, such as in myelodysplastic syndromes (MDS) or myelofibrosis (MF), can result from defects at any stage in the pathway. However, current treatments target distinct stages of erythropoiesis, resulting in some patients being unresponsive to treatment; targeting multiple stages of erythropoiesis may provide a better treatment option.
The TGF-β superfamily regulates erythropoiesis by maintaining a balance between progenitor quiescence and differentiation. KER-050, a modified ActRIIA ligand trap, is designed to promote erythropoiesis through inhibition of TGF-β ligands that signal though SMAD2/3, including activins and GDFs. In a Phase 1 clinical study, administration of KER-050 to healthy volunteers led to a robust, rapid, and sustained increase in RBCs and hemoglobin (HGB) as well as an increase in platelets, potentially suggesting a broader effect of KER-050 on hematopoiesis.
Aims
Determine the durability of effect and mechanism of action of KER-050 on erythropoiesis.
Methods
C57BL/6 male mice (12-week-old) were treated with a single dose of either vehicle or a research form of KER-050 (RKER-050). Peripheral blood was evaluated for reticulocytes (RET), RBCs, and HGB, and bone marrow (BM) erythroblasts were analyzed by flow cytometry, at multiple time points from 12 hours (hr) through day 51. Erythropoietin (Epo) levels were measured in serum.
Results
Treatment with RKER-050 resulted in rapid and sustained increases in RBCs and HGB, observed from 12hr through day 51. Within 12hr, RBCs (+8%) and HGB (+9%) were significantly increased. This response corresponded to a 20% reduction in BM proerythroblasts and erythroblasts (TER119+ cells) and a concomitant 18% increase (compared to vehicle) in circulating RETs, supporting that the maturation of these late-stage precursors contributed to the rapid RBC effect. Indeed, analysis of specific BM populations showed a general shift in the TER119+ cells from early to late erythroblast populations.
Within 48hr, the number of BM TER119+ cells increased by 37% compared to vehicle, demonstrating that precursor pools reduced at 12hr were quickly restored. In parallel, the initial increase in RETs observed at 12hr were transiently reduced (-15%), implying continued late-stage maturation of RETs to RBCs. This continued movement of earlier stage erythroid precursors into later stages of the pathway continued, with RET levels again replenished and TER119+ cells reduced by 48hr, likely supporting that the robust and sustained response in RBCs was due to administration of KER-050.
In addition to RKER-050 promoting differentiation of erythroid precursors to elicit its effect on RBCs, a RKER-050-mediated upregulation of Epo may also be contributing to the sustained increase in RBCs. Epo does not appear to play a role in the initial rapid RBC increase since Epo upregulation was not observed until day 4; however, Epo was increased from day 4 through day 37 which could indicate a role in sustaining the RKER-050-mediated increase in RET (+4%), RBCs (+8%), and HGB (+3%) to at least day 51.
Conclusion
In these studies, we observed that RKER-050 had a rapid and durable effect on erythropoiesis. The observed effects of RKER-050 on multiple stages of erythroblast maturation (both early- and late-stage) and increase in circulating EPO provide a strong rationale for investigating KER-050 as a treatment for ineffective hematopoiesis in MDS and MF.
Keyword(s): Erythropoieisis, MDS, Myelofibrosis, Transforming growth factor-