Eltombopag: Novel Mode of Action on Normal and Aplastic Anemia Hematopoietic Stem Cells

Eltombopag：对正常和再生障碍性贫血造血干细胞的新作用模式

• 批准号: 10676888
• 负责人: Babal K Jha
• 金额: $ 65.88万
• 依托单位: CLEVELAND CLINIC LERNER COM-CWRU
• 依托单位国家: 美国
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-08-15 至 2027-05-31
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10676888
• 关键词: Affect; Aftercare; Agonist; Aplastic Anemia; Ascorbic Acid; Binding; Biochemical; Biological; Biological Models; Blood Cells; Bone marrow failure; CD34 gene; Catalytic Domain; Cell Line; Cell Lineage; Cells; Chemicals; Clinical; Clinical Data; Clinical Research; Coupled; Cryoelectron Microscopy; Crystallography; DNA; DNA methylation profiling; Dependence; Dioxygenases; Elderly; Engraftment; Enhancers; Enzymes; Epigenetic Process; Failure; Gene Expression Profile; Gene Mutation; Genes; Hematology; Hematopoiesis; Hematopoietic; Hematopoietic stem cells; Human; Hypermethylation; Immune; Immune mediated destruction; In Vitro; In complete remission; Individual; Iron; Iron Chelating Agents; Iron Chelation; Kinetics; MPL gene; Mediating; Modeling; Molecular; Mus; Myelogenous; Neoplasms; Pathway interactions; Patients; Peptides; Pharmaceutical Preparations; Platelet Count measurement; Population; Production; Proliferating; Property; Proteins; RNA; Radiation; Recovery; Refractory; Relapse; Residual state; Resolution; Role; Signal Transduction; Somatic Mutation; System; Testing; Therapeutic; Therapeutic immunosuppression; Thrombocytopenic Purpura; alpha ketoglutarate; analog; base; bone marrow failure syndrome; clinically relevant; cofactor; demethylation; design; epigenetic regulation; extracellular; hematopoietic stem cell expansion; high throughput screening; improved; in vivo; in vivo Model; inhibitor; leukemia; loss of function mutation; mRNA Expression; mimetics; mouse model; novel; polypeptide; promoter; receptor-mediated signaling; response; small molecule; stem cells; success; transcriptome sequencing

Summary Idiopathic aplastic anemia (AA) is characterized by immune-mediated hematopoietic stem and progenitor cells (HSPCs) destruction resulting in deficiencies across all hematopoietic lineages and bone marrow failure. Despite of the therapeutic successes of immunosuppressive therapies (IST), approximately one third of patients remain refractory and many of the responses are incomplete. Recently, a synthetic thrombopoietin receptor (TPOR) agonist, Epag has been shown to be effective in AA. In addition to the anticipated effect on platelet counts, Epag also produced remarkable tri-lineage hematopoiesis. These effects expanded the indication spectrum of Epag from immune thrombocytopenic purpura to AA, establishing this drug as an essential hematologic therapeutic. Recent studies demonstrate that Epag’s hematopoietic activity is also observed in murine models despite the lack of binding to murine TpoR. We confirmed similar effects in murine cells where Epag treatment remarkably expanded HSCs without any effect on the TpoR signaling. These observations suggested that a significant part of Epag’s activities are TPOR independent, in contrast to peptide TPO analogs, e.g., romiplostin. These TPOR independent effects of Epag were hypothesized to be due to its iron chelating properties, but the molecular mechanism as to how this iron-binding could drive the HSPCs expansion remains speculative. Epag effects on intracellular iron may affect certain iron-dependent epigenetic pathway/s that promote HSPCs self-replication. For instance, TET-dioxygenases (TET1-3) are Fe2+- and α- ketoglutarate (αKG) dependent DNA-dioxygenases, which mediate CpG demethylation of promoters and enhancers in HSPCs. Consequently, by changing gene expression patterns, TETs control HSPCs expansion and differentiation. TET2 is the most abundant TET-dioxygenase in HSPCs, and somatic loss-of-function (LOF) mutations of this gene frequently occur in myeloid neoplasia and clonal hematopoiesis of indeterminate potential (CHIP), a prodromal condition in otherwise healthy elderly individuals characterized by high progression rate to a frank leukemia. Our proposal is designed to determine the effects of Epag on normal hematopoiesis mediated by its ability to inhibit TET-activity. Based on our analysis of clinical data coupled with biochemical analysis we hypothesize that, Epag-mediated TET- inhibition is responsible for tri-lineage response in AA via HSC expansion and on the biochemical level decreased 5hmC content leading to hypermethylation as a result of direct inhibition of TET2. Our current proposal will provide a proof of concept for the reversible transient TET-inhibition as a basis for HSC expansion that may restore normal hematopoiesis.

概括 特发性性性贫血（AA）的特征是免疫介导的造血茎和 祖细胞（HSPCS）破坏，导致所有造血谱系缺乏 和骨髓衰竭。尽管免疫抑制疗法取得了治疗成功 （IST），大约三分之一的患者仍然是难治性的，许多反应是 不完整。最近，已显示了EPAG的合成血栓蛋白受体（TPOR）激动剂 在AA中有效。除了预期对血小板计数的影响，EPAG还产生了 显着的三轮造血。这些效果扩大了EPAG的指示光谱 从免疫血小板减少紫癜到AA，将这种药物确立为必不可少的血液学 治疗性。最近的研究表明，在 鼠模型尽管缺乏与鼠Tpor结合的结合。我们在鼠中确认了类似的影响 EPAG处理明显扩展的HSC的细胞对TPOR信号传导没有任何影响。 这些观察结果表明，EPAG活动的很大一部分是独立的， 与胡椒TPO类似物（例如romiplostin）相反。 EPAG的这些独立效应 假设是由于其铁螯合特性引起的，但是分子机制 这种铁结合如何驱动HSPCS的扩展仍然是投机性的。 EPAG的影响 细胞内铁可能会影响促进的某些铁依赖性表观遗传途径 HSPC自我复制。例如，TET-dioxygyass（TET1-3）是Fe2+ - 和α- 酮谷酸酯（αkg）依赖性DNA-二氧酶，介导CpG脱甲基化 HSPC中的启动子和增强子。因此，通过改变基因表达 模式，TET控制HSPCS的扩展和分化。 TET2是最丰富的 HSPC中的TET-二氧酶和该基因的躯体丧失功能丧失（LOF）突变 经常发生在不确定潜力的髓样肿瘤和克隆造血 （芯片），其他健康的人的前驱状况，以此为特征 弗兰克白血病的高进展率。我们的建议旨在确定 EPAG对正常造血作用的影响，其抑制TET活性的能力介导。 基于我们对临床数据的分析，加上生化分析，我们假设这一点， EPAG介导的TET-抑制作用是通过HSC扩展在AA中的三维响应的原因 并且在生化水平上提高了5HMC含量，从而导致高甲基化。 直接抑制TET2。我们当前的建议将为可逆的概念证明 瞬态TET抑制作用作为HSC扩张的基础，可能会恢复正常的造血。