Tyrosyl-DNA phosphodiesterase 2 (TDP2) repairs topoisomerase II (Top2) mediated DNA damages, including double-strand breaks (DSBs) that underpin the anticancer mechanism of clinical Top2 poisons such as etoposide (ETP). Inhibition of TDP2 could sensitize cancer cells toward Top2 poisons by increasing Top2 cleavage complex. We have previously identified isoquinoline-1,3-dione as a selective inhibitor type of TDP2. However, the reported structure-activity relationship (SAR) was limited to simple substitutions on the isoquinoline-1,3-dione core. Herein, we report the extended SAR consisting of the synthesis and testing of a total of 50 analogs featuring N-2 and C-4 modifications. Major SAR observations include the loss of potency upon N-2 substitution, the lack of inhibition with C-4 enamine analogs (subtype 11), or any other C-4 modifications (subtypes 13-15) except for the benzylidene substitution (subtype 12), where eight analogs showed low micromolar potency. The best analog, 12q, inhibited TDP2 with an IC₅₀ of 4.8 μM. Molecular modeling was performed to help understand the observed SAR trends. Overall, these SAR observations which could significantly benefit future work on the design of improved TDP2 inhibitors.

酪氨酰-DNA 磷酸二酯酶 2 (TDP2) 修复拓扑异构酶 II (Top2) 介导的 DNA 损伤，包括支撑临床 Top2 毒物如依托泊苷 (ETP) 的抗癌机制的双链断裂 (DSB)。抑制 TDP2 可以通过增加 Top2 裂解复合物使癌细胞对 Top2 毒物敏感。我们之前已将异喹啉-1,3-二酮确定为 TDP2 的选择性抑制剂类型。然而，报告的结构-活性关系 (SAR) 仅限于异喹啉-1,3-二酮核心上的简单替换。在这里，我们报告了扩展的 SAR，包括对总共 50 种具有 N-2 和 C-4 修饰的类似物的合成和测试。主要的 SAR 观察结果包括 N-2 取代后效力的丧失、C-4 烯胺类似物（亚型11)，或任何其他 C-4 修饰（亚型13-15），但苯亚甲基取代（亚型12 ）除外，其中 8个类似物显示出低微摩尔效力。最好的类似物12q以 4.8 μM的 IC ₅₀抑制 TDP2 。进行分子建模以帮助了解观察到的 SAR 趋势。总体而言，这些 SAR 观察结果可以显着有益于未来设计改进的 TDP2 抑制剂的工作。