组蛋白赖氨酸甲基转移酶DOT1L特异性催化组蛋白H3第79位赖氨酸（H3K79）发生甲基化，可作为混合细胞系白血病（MLL）的潜在治疗靶标。DOT1L小分子抑制剂及调控机制的研究，为MLL相关性白血病的治疗提供了新的思路。目前，针对DOT1L的抑制剂设计主要围绕辅酶S-腺苷甲硫氨酸的类似物结构改造开展，已报道的活性化合物结构类型单一，普遍存在选择性差、药代性质不好的缺点。此外，DOT1L的活性位点具有开放性高、柔性大和极性强的结构特点，使用传统的合理药物设计方法发现靶向DOT1L的新化学实体的难度较大。针对这些问题，本项目拟通过发展和应用甲基转移酶专用药物设计方法，针对已发现的具有新颖骨架的DOT1L抑制剂进行结构活性关系分析和ADMET性质优化，开展分子、细胞和动物水平的抗肿瘤活性评价及表观调控作用机制研究，以期获得高效、高特异性、高成药性的新型DOT1L抑制剂药物候选化合物。

Disruptor of telomeric silencing 1-like (DOT1L) is an evolutionarily conserved histone methyltransferase (HMT) that specifically catalyzes the methylation of the histone H3-lysine79 (H3K79) residue in the core domain, which plays an important role in transcriptional regulation, cell cycle regulation, and the DNA damage response, and is proposed to be a catalytic driver of leukemogenesis in mixed lineage leukemia (MLL). Since the discovery of the critical role of DOT1L in MLL leukemia, research has focused on identifying inhibitors of DOT1L. Because almost all methyltransferases use S-adenosyl-L-methionine (SAM) as the methyl donor (enzyme cofactor), a common strategy for designing DOT1L inhibitors is to develop SAM analogs that may compete with SAM. To date, a variety of DOT1L inhibitors have been reported, but most are SAM derivatives with an adenosine group, and their selectivity profile and pharmacokinetic properties are unsatisfactory, e.g., showing low oral bioavailability and high clearance rates. Since the structural diversity of DOT1L inhibitors remains limited, there remains an urgent need to develop new DOT1L inhibitors with novel scaffolds. Meanwhile, there are some peculiarities to the active site of DOT1L, compared to general ligand sites of drug targets, which make traditional structure-based drug design (SBDD) approaches toward DOT1L particularly challenging: extreme flexibility, a large number of polar residues with high charge density, extensive solvent exposure of its binding site. Therefore, widely used docking programs and scoring functions, which account differently for these types of interactions, may not perform as well for DOT1L-ligand complexes. To address these issues, we have developed a customized SBDD approach called SAM score for discovering novel inhibitors of HMTs, and successfully applied this approach in discovering four DOT1L inhibitors with novel scaffolds. In this proposed project, we aim to further employ this approach to guide the lead optimization of our previously identified DOT1L inhibitors, further carry out molecular, cellular, and animal level of antitumor evaluations, investigate their epigenetic regulation mechanisms, and, in the end, obtain new DOT1L inhibitors with high efficiency and specificity, and good drugability properties.