Discovery of Novel Disruptor of Silencing Telomeric 1‑Like (DOT1L) Inhibitors using a Target-Specific Scoring Function for the (<i>S</i>)‑Adenosyl‑l‑methionine (SAM)-Dependent Methyltransferase Family

The disruptor of telomeric silencing 1-like (DOT1L) protein is a histone H3K79 methyltransferase that plays a key role in transcriptional elongation and cell cycle regulation and is required for the development and maintenance of MLL-rearranged mixed lineage leukemia. Much effort has been dedicated toward discovering novel scaffold DOT1L inhibitors using different strategies. Here, we report the development and application of a target-specific scoring function, the SAM score, for (S)-adenosyl-l-methionine (SAM)-dependent methyltransferases, for the discovery of novel DOT1L inhibitors. On the basis of the SAM score, we successfully identified a novel class of DOT1L inhibitors with a scaffold of [1,2,4]-triazolo-[3,4-b]­[1,3,4]-thiadiazole, in which compound 6 exhibits an IC50 value of 8.3 μM with selectivity versus other tested SAM-dependent methyltransferases. In cellular studies, 6 selectively targets DOT1L, blocks the proliferation of mixed lineage leukemia cell lines, and causes cell cycle arrest and apoptosis. Moreover, we analyzed the putative binding modes of 6 and its analogues obtained by molecular docking, which may assist with the future development of DOT1L inhibitors with improved potency and selectivity profiles.端粒沉默干扰因子1样（DOT1L）蛋白是一种组蛋白H3K79甲基转移酶，在转录延伸与细胞周期调控中发挥关键作用，且是MLL重排型混合谱系白血病发育与维持所必需的蛋白。目前学界已通过多种策略致力于开发新型骨架型DOT1L抑制剂。本研究报道了一种针对(S)-腺苷-L-甲硫氨酸（(S)-adenosyl-L-methionine，SAM）依赖型甲基转移酶的靶点特异性评分函数——SAM评分，并将其用于新型DOT1L抑制剂的发现。基于该SAM评分，我们成功鉴定出一类全新的DOT1L抑制剂，其母核结构为[1,2,4]-三唑并-[3,4-b]­[1,3,4]-噻二唑；其中化合物6对其他受试SAM依赖型甲基转移酶展现出良好选择性，其半数抑制浓度（IC50）为8.3 μM。细胞实验结果表明，化合物6可选择性靶向DOT1L，抑制混合谱系白血病细胞系增殖，并诱导细胞周期阻滞与细胞凋亡。此外，我们通过分子对接分析了化合物6及其类似物的推定结合模式，该结果可为后续开发活性与选择性更优的DOT1L抑制剂提供参考。