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

摘要 剪接因子SF3B1(SF3B1MT)突变，发生在20%的骨髓增生异常患者中 综合征(MDS)是MDS-RS的特征，MDS-RS是MDS的一种亚型，其特征是 骨髓中的环状铁粒母细胞(RS)。SF3B1MT存在于不同类型的造血细胞中，但 优先解除对红系祖细胞的管制。尽管MDS-RS的白血病倾向较低 转化，大多数MDS-RS患者贫血严重，依赖定期输血 尽管铁超载和其他不利后果的风险增加。 唯一被批准用于治疗不符合条件的输血依赖MDS-RS患者的药物 对红细胞生成刺激剂有效或无效的药物是luspatercept，一种转化生长因子β信号的抑制剂。 然而，luspatercept的应答率不到40%，这突显了替代方案的必要性 可以减轻这些患者红系分化受损的治疗方案。 在我们之前的研究中，我们发现EIF2AK1对血红素缺乏的反应是一个潜在的驱动因素 SF3B1MT诱导的红系分化停滞。因此，我们假设药物抑制作用 EIF2AK1激活克服了SF3B1突变MDS-RS患者的无效红细胞生成。为了测试这一点 假设，我们将追求开发一种EIF2AK1活性的小分子抑制剂的特定目标 SF3B1突变MDS样本的概念验证研究。这一目标的发现将提供一条直接的路线 展望未来适合临床开发的化合物。 我们已经与MD Anderson癌症中心的应用癌症科学研究所合作开发 MDS-RS中靶向EIF2AK1通路的小分子。我们的多学科团队已经确定 几种EIF2AK1抑制剂，具有低纳摩尔效力，高渗透性和无外排，并具有 相对于EIF2AK蛋白激酶家族的其他成员，具有良好的选择性。在拟议的工作中，我们 将使用细胞分析从功能上验证这些候选细胞(使用原代细胞、诱导多能性 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， 这项研究将使EIF2AK1活性的第一个抑制剂的开发成为可能。 这项拟议的工作对开发治疗方法以实现持久的血液学具有重要意义 依赖输血的MDS-RS患者的反应。鉴于EIF2AK1抑制是最大的 到目前为止，镰状细胞性贫血的治疗方法很有希望，我们的工作结果可能会有广泛的 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.