Novel Small-Molecule Probes Targeting Oncogenic Fusion MLL in Pediatric Leukemia

急性白血病，包括急性髓系白血病(AML)和淋巴细胞性白血病(ALL)是最常见的(1/3) 儿童和青少年中的癌症。尤其是由染色体易位引起的白血病 混合血统白血病(MLL)基因占婴儿白血病的~75%，占儿童/成人白血病的~10%。 预后很差。与其他儿科ALL相比，MLL重排组的5年生存率约为90% ALL只有40%，对于非常年幼的婴儿，存活率甚至是20%。MLL重排的AML患者有 与其他AML相比，临床结果同样差。目前的治疗方法是传统的化疗药物，这种药物会杀死所有人 快速增殖的细胞，包括骨髓和其他器官中的正常干细胞。这会导致严重的 毒副作用，甚至因诱变而导致的继发性癌症。因此，迫切需要 寻找毒性较低的针对MLL癌基因的药物，这种基因会导致恶性肿瘤。MLL癌基因由MLL融合基因组成 带有另一种基因。AF9(~30%)和AF4(35%)是MLL最常见的融合伙伴。这些蛋白质， 与DOT1L(已知的白血病药物靶点)相互关联，构成SO-1L。 被称为超延长复合体(SEC)，它导致白血病的恶性基因表达。上一首 研究表明AF9和AF4或DOT1L之间的蛋白质-蛋白质相互作用在MLL-白血病中起关键作用，但 在正常细胞中是不必要的。该项目旨在发现和开发第一个小分子抑制剂 阻断AF9-AF4/DOT1L相互作用，有望成为生物研究的新型化学探针 AF9/SEC，或低毒的MLL重排白血病的潜在治疗药物。具体目标1是 使用合理的设计和药物化学来寻找有效的、类似药物的AF9抑制剂。目标2是执行 生化、X-射线和核磁共振结构研究以表征抑制剂与AF9的相互作用。目标3是执行 以细胞为基础的分析，以测试选定的有效抑制剂的生物活性，目标4是执行 药代动力学、毒性和抗肿瘤活性测试以确定有用的化学探针或潜在药物 候选人。

Acute leukemia, including acute myeloid (AML) and lymphoid leukemia (ALL), is the most common (1 out of 3) cancer in children and adolescents. Particularly, leukemia caused by chromosome translocations involving mixed lineage leukemia (MLL) gene accounts for ~75% of leukemia in infants and ~10% in children/adults with a poor prognosis. Compared to other pediatric ALL with a 5-year survival of ~90%, that for MLL-rearranged ALL is only ~40%, and for very young infants, the survival is even <20%. MLL-rearranged AML patients have similarly poor clinical outcomes to other AMLs. Current treatments are conventional chemo-drugs, which kill all rapidly proliferating cells including normal stem cells in bone marrow and other organs. This causes severe toxicities, side effects, and even secondary cancer due to mutagenesis. There is therefore a pressing need to find less toxic drugs targeting MLL-oncogene that drives the malignancy. MLL-oncogene consists of MLL fused with another gene. AF9 (~30%) and AF4 (35%) are the most frequent fusion partners of MLL. These proteins, together with DOT1L (a known drug target for the leukemia), associate with each other and constitute the so- called super elongation complex (SEC), which causes malignant gene expression in leukemia. Previous studies show the protein-protein interactions between AF9 and AF4 or DOT1L is critical to MLL-leukemia, but is dispensable in normal cells. This project aims to find and develop the first small-molecule inhibitors that disrupt the AF9-AF4/DOT1L interaction, which could be novel chemical probes for biological studies of AF9/SEC, or potential therapeutics for MLL-rearranged leukemia with a low toxicity. The Specific Aim 1 is to use rational design and medicinal chemistry to find potent, drug-like inhibitors of AF9. Aim 2 is to perform biochemical, X-ray and NMR structural studies to characterize inhibitor-AF9 interactions. Aim 3 is to perform cell-based assays to test biological activities of selected potent inhibitors, and Aim 4 is to perform pharmacokinetics, toxicity, and antitumor activity testing to identify useful chemical probes or potential drug candidates.