Discovery of small molecules targeting the histone acetylation reader ENL

项目总结 混合系白血病(MLL)基因重排约占婴儿急性白血病的80% 淋巴细胞性白血病(ALL)和35-50%的婴儿急性髓系白血病(AML)。患者生育 MLL基因重排与预后不良有关，尤其是对 标准治疗。针对这一亚型致命疾病的最新有效治疗方法仍然缺乏。 在分子上，MLL的染色体间易位导致MLL的N末端与 C末端的各种融合伙伴，这是众所周知的“驱动”病变的疾病。在更多中 超过70个MLL融合伙伴，一小部分融合占大多数白血病病例的原因。总体而言，超过90% MLL重排只涉及四个融合伙伴：AFF1、AF9、ENL和AF10，所有这些都是 超延长复合体(SEC)或组蛋白H3K79甲基转移酶DOT1L的复合体。据信， 这些MLL融合通过“劫持”SEC或DOT1L复合体来促进 MLL融合的靶基因异常激活，导致白血病的发病。 申请人和其他人的研究表明，ENL是SEC和 DOT1L复合体对于MLL融合的致癌功能至关重要。ENL包含一个进化上的 保守的叶芝领域。申请人发现enl的叶芝结构域起到阅读器的作用 组蛋白乙酰化(Cell，2014,159：558-71)。重要的是，叶芝的乙酰化阅读功能 结构域对于MLL重排的白血病细胞的生长和生存是必不可少的(自然，2017,543：265-269)。 这些关键发现提供了概念证据，即以enl的Yeats结构域为目标是一种潜在的 治疗MLL重排白血病的有价值的治疗选择。 在FOA的范围内，这项提议的目标是开发有效的和选择性的ENL抑制剂 叶芝的领域。该建议的具体目标是：(1)对ENL进行高通量筛选 小分子抑制剂；(2)通过正交法验证和评估候选HITS；以及(3)表征 在基于细胞的分析中有命中率。从拟议的研究中获得的抑制剂将作为工具化合物 研究enl促进MLL融合蛋白在基因调控和疾病中的作用及其机制 维修。这些化合物还将为进一步开发小分子药物提供基础 MLL易位白血病的靶向治疗。临床前研究表明BET抑制剂表现出有限的 作为单一药物的有效性。由该项目提供的选择性和有效的enl抑制剂将是一个重要的工具。 为验证ENL和BET抑制剂的协同作用，提供一种创新的治疗策略 MLL重排白血病的治疗。

PROJECT SUMMARY The mixed-lineage leukemia (MLL) gene rearrangements account for approximately 80% of infant acute lymphoblastic leukemia (ALL) and 35-50% of infant acute myeloid leukemia (AML). Patients bearing rearrangements of the MLL gene are associated with dismal prognosis and particularly poor response to standard treatments. Up-to-date, effective therapies for this subtype of fatal disease are still lacking. Molecularly, inter-chromosomal translocations of MLL lead to in frame fusions of the N-terminus of MLL to the C-terminus of various fusion partners, which are known as the “driver” lesions of the diseases. Among more than 70 MLL fusion partners, a small subset of fusions account for most leukemogenic cases. In ALL, over 90% MLL rearrangements involve only four fusion partners: AFF1, AF9, ENL, and AF10, all are components of the super elongation complex (SEC) or the complex of the histone H3K79 methyltransferase DOT1L. It is believed that these MLL fusions share a common pathway by “hijacking” SEC or the DOT1L complex to promote aberrant activation of the target genes of MLL fusions, leading to the pathogenesis of leukemias. Studies from the applicant and others have demonstrated that ENL, a stoichiometric component of SEC and the DOT1L complex, is critical for the oncogenic function of the MLL-fusions. ENL contains an evolutionally conserved YEATS domain. The applicant found that the YEATS domain of ENL functions as a reader of histone acetylation (Cell, 2014, 159:558-71). Importantly, the acetylation reading function of the YEATS domain is essential for growth and survival of the MLL-rearranged leukemic cells (Nature, 2017, 543:265-269). These key findings provide the proof of concept that targeting the YEATS domain of ENL is a potentially valuable therapeutic option in treatment of MLL-rearranged leukemias. The goal of this proposal within the scope of this FOA is to develop potent and selective inhibitors of the ENL YEATS domain. The specific aims of the proposal are to (1) conduct a high-throughput screening for ENL small-molecule inhibitors; (2) validate and evaluate candidate hits by orthogonal assays; and (3) characterize hits in cell-based assays. The inhibitors obtained from the proposed study will serve as tool compounds to study the functions and mechanisms of ENL in promoting MLL-fusion proteins in gene regulation and disease maintenance. These compounds will also provide the basis for further development of small molecules for targeted therapies of MLL-translocated leukemias. Preclinical studies suggest that BET inhibitors exhibit limited efficacy as single agents. Selective and potent ENL inhibitors provided by this project will be an important tool to test the synergistic effect of ENL and BET inhibitions, providing an innovative therapeutic strategy for the treatment of MLL-rearranged leukemias.