A series of novel benzo[c][1,2,5]oxadiazole derivatives were designed, synthesized, and biologically evaluated as inhibitors of PD-L1. Among them, compound L7 exhibited 1.8 nM IC₅₀ value in a homogeneous time-resolved fluorescence (HTRF) assay, which was 20-fold more potent than the lead compound BMS-1016. In the surface plasmon resonance (SPR) assay, L7 bound to human PD-L1 (hPD-L1) with a K_D value of 3.34 nM, without showing any binding to hPD-1. In the cell-based coculture assay, L7 blocked PD-1/PD-L1 interaction with an EC₅₀ value of 375 nM, while BMS-1016 had an EC₅₀ value of 2075 nM. Moreover, compound L24, an ester prodrug of L7, was orally bioavailable and displayed significant antitumor effects in tumor models of syngeneic and PD-L1 humanized mice. Mechanistically, L24 exhibited significant in vivo antitumor effects probably through promoting antitumor immunity. Together, this series of benzoxadiazole PD-L1 inhibitors holds promise for tumor immunotherapy. Preclinical trials with selected compounds are ongoing in our laboratory.

中文翻译：

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苯并[c][1,2,5]恶二唑衍生物作为具有体内抗肿瘤活性的强效PD-L1抑制剂的合成、生物学评价和机理研究

设计、合成了一系列新型苯并[ c ][1,2,5]恶二唑衍生物，并对其作为 PD-L1 抑制剂进行了生物学评估。其中，化合物L7在均相时间分辨荧光 (HTRF) 测定中表现出 1.8 nMIC ₅₀值，其效力是先导化合物BMS-1016 的20 倍。在表面等离子共振 (SPR) 分析中，L7与人 PD-L1 (hPD-L1) 结合，K _D值为 3.34 nM，但未显示与 hPD-1 的任何结合。在基于细胞的共培养试验中，L7阻断了 PD-1/PD-L1 相互作用，EC ₅₀值为 375 nM，而BMS-1016具有 EC ₅₀值 2075 nM。此外，L7的酯前药化合物L24具有口服生物可利用性，并在同基因和 PD-L1 人源化小鼠的肿瘤模型中显示出显着的抗肿瘤作用。从机制上讲，L24可能通过促进抗肿瘤免疫而表现出显着的体内抗肿瘤作用。总之，这一系列苯并恶二唑 PD-L1 抑制剂有望用于肿瘤免疫治疗。我们的实验室正在进行选定化合物的临床前试验。