X 射线晶体结构指导发现新型吲哚类似物作为秋水仙碱结合位点微管蛋白抑制剂并具免疫增强及抗黑色素瘤作用

A series of novel indole analogues were discovered as colchicine-binding site inhibitors of tubulin. Among them, 3a exhibited the highest antiproliferative activity (average IC 50 = 4. 5 nM), better than colchicine (IC 50 = 65. 3 nM). The crystal structure of 3a in complex with tubulin was solved by X-ray crystallography, which explained the improved binding affinity of 3a to tubulin and thus its higher anticancer activity (IC 50 = 4.

5 nM) than the lead compound 12b (IC 50 = 32. 5 nM). In vivo , 3a (5 mg/kg) displayed significant antitumor efficacy against B16-F10 melanoma with a TGI of 62. 96% and enhanced the antitumor efficacy of a small-molecule PD-1/PD-L1 inhibitor NP19 (TGI = 77. 85%).

Moreover, 3a potentiated the antitumor immunity of NP19 by activating the tumor immune microenvironment, as demonstrated by the increased tumor-infiltrating lymphocytes (TIL). Collectively, this work shows a successful example of crystal structure-guided discovery of a novel tubulin inhibitor 3a as a potential anticancer and immune-potentiating agent.