Developing an inhibitor of EIF2AK1 to overcome ineffective erythropoiesis in myelodysplastic syndromes with ringed sideroblasts

摘要 剪接因子SF 3B 1（SF 3B 1 MT）突变，发生在20%的骨髓增生异常患者中 MDS综合征（MDS）是MDS-RS的标志，MDS-RS是一种MDS亚型，其特征在于 骨髓中的环形铁粒幼细胞（RS）。SF 3B 1 MT存在于不同的造血细胞类型中， 优先去调节红系祖细胞。尽管MDS-RS对白血病的倾向性较低， 在转化过程中，大多数MDS-RS患者患有严重贫血，并依赖定期输血 尽管铁超载和其他不良后果的风险增加。 唯一获批用于治疗不符合条件的输血依赖性MDS-RS患者的药物 对红细胞生成刺激剂没有反应的是luspatercept，一种TGFβ信号传导抑制剂。 然而，luspatercept的反应率低于40%，这强调了替代治疗的必要性。 可以减轻这些患者红细胞分化受损的治疗选择。 在我们之前的研究中，我们确定了EIF 2AK 1对血红素缺乏的反应是导致EIF 2AK 1表达增加的潜在驱动因素。 SF 3B 1 MT诱导的红系分化停滞。因此，我们假设， EIF 2AK 1激活克服了SF 3B 1突变型MDS-RS患者的无效红细胞生成。为了验证这一 假设，我们将追求开发EIF 2AK 1活性的小分子抑制剂的具体目标， 在SF 3B 1突变型MDS样本中的概念验证研究。这一目标的发现将提供一条直接的路线， 对未来适合临床开发的化合物的展望。 我们与MD安德森癌症中心的应用癌症科学研究所合作， MDS-RS中靶向EIF 2AK 1通路的小分子。我们的多学科团队已经确定了 几种具有低纳摩尔效力的EIF 2AK 1抑制剂，具有高度渗透性和无外排，并且具有 相对于蛋白激酶的EIF 2AK家族的其他成员具有良好的选择性。在工作中，我们 将使用细胞测定法（采用原代细胞、诱导多能细胞、细胞外基质和细胞外基质）在功能上验证这些候选物。 干细胞和基因工程细胞系），这是我们在过去3年中开发的。如果成功， 本研究将能够开发出第一种EIF 2AK 1活性抑制剂。 这项工作对开发治疗方法以实现持久的血液学治疗具有重要意义。 输血依赖性MDS-RS患者的反应。考虑到EIF 2AK 1抑制是最重要的 有希望的治疗方法镰状细胞贫血的日期，我们的工作结果可能有广泛的 应用范围。

ABSTRACT Mutations in the splicing factor SF3B1 (SF3B1MT), which occur in 20% of patients with myelodysplastic syndromes (MDS), are the hallmarks of MDS-RS, an MDS subtype characterized by the accumulation of ringed sideroblasts (RS) in the bone marrow. SF3B1MT are found in different hematopoietic cell types but preferentially deregulate erythroid progenitors. Although MDS-RS has a low propensity for leukemic transformation, most patients with MDS-RS have severe anemia and depend on regular blood transfusions despite the increased risk of iron overload and other adverse outcomes. The only agent approved for the treatment of transfusion-dependent MDS-RS patients who are ineligible for or have no response to erythropoiesis-stimulating agents is luspatercept, an inhibitor of TGFβ signaling. However, luspatercept has a response rate of less than 40%, which underscores the need for alternative treatment options that can alleviate impaired erythroid differentiation in these patients. In our previous study, we identified the EIF2AK1 response to heme deficiency as a potential driver of the SF3B1MT-induced arrest of erythroid differentiation. We therefore hypothesize that pharmacologically inhibiting EIF2AK1 activation overcomes ineffective erythropoiesis in patients with SF3B1-mutant MDS-RS. To test this hypothesis, we will pursue the specific aim of developing a small-molecule inhibitor of EIF2AK1 activity for proof-of-concept studies in SF3B1-mutant MDS samples. The findings of this aim will provide a direct line of sight to future compounds suitable for clinical development. We have partnered with the Institute of Applied Cancer Science at MD Anderson Cancer Center to develop small molecules targeting the EIF2AK1 pathway in MDS-RS. Our multidisciplinary team has already identified several EIF2AK1 inhibitors that have low nanomolar potency, are highly permeable and free of efflux, and have good selectivity relative to other members of the EIF2AK family of protein kinases. In the proposed work, we will functionally validate these candidates using cellular assays (employing primary cells, induced pluripotent stem cells, and genetically engineered cell lines) that we have developed over the last 3 years. If successful, this study will enable the development of the first inhibitor of EIF2AK1 activity. The proposed work has implications for the development of therapies to achieve long-lasting hematological responses in transfusion-dependent MDS-RS patients. Given that EIF2AK1 inhibition is one of the most promising therapeutic approaches for sickle cell anemia to date, the results of our work may have a broad spectrum of application.