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 特发性再生障碍性贫血（AA）的特点是免疫介导的造血干细胞和 祖细胞 (HSPC) 破坏导致所有造血谱系缺陷 尽管免疫抑制疗法取得了成功，但仍存在骨髓衰竭。 (IST)，大约三分之一的患者仍然难治，并且许多反应是 最近，一种合成的血小板生成素受体（TPOR）激动剂 Epag 已被证明。 除了对血小板计数的预期效果外，Epag 还产生了对 AA 有效的效果。 显着的三系造血作用扩大了 Epag 的适应症范围。 从免疫性血小板减少性紫癜到 AA，使该药物成为一种重要的血液学药物 最近的研究表明，Epag 的造血活性也在 尽管缺乏与小鼠 TpoR 的结合，但我们在小鼠模型中证实了类似的效果。 Epag 处理显着扩增 HSC 的细胞，但对 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于 TPOR 的， 与肽 TPO 类似物（例如 romiplostin）相比，Epag 的这些 TPOR 独立作用。 因其铁螯合特性而受到攻击，但其分子机制 这种铁结合如何驱动 HSPC 的扩张仍然是推测。 细胞内铁可能会影响某些铁依赖性表观遗传途径，从而促进 HSPC 自我复制，例如，TET-双加氧酶 (TET1-3) 是 Fe2+- 和 α-。 酮戊二酸 (αKG) 依赖性 DNA 双加氧酶，介导 CpG 去甲基化 通过改变基因表达来测试 HSPC 中的启动子和增强子。 模式中，TETs 控制 HSPC 的扩增和分化，TET2 最为丰富。 HSPC 中的 TET 双加氧酶以及该基因的体细胞功能丧失 (LOF) 突变 常发生于骨髓瘤和不确定潜力的克隆性造血 （CHIP），一种健康老年人的前驱症状，其特征是 我们的建议旨在确定白血病的高进展率。 Epag 通过其抑制 TET 活性的能力介导对正常造血的影响。 根据我们对临床数据的分析以及生化分析，我们认为， Epag 介导的 TET 抑制通过 HSC 扩增导致 AA 中的三谱系反应 并在生化水平上降低 5hmC 含量，从而导致高甲基化 我们目前的提议将为可逆性提供概念证明。 短暂的 TET 抑制作为 HSC 扩增的基础，可以恢复正常的造血功能。