The inhibition of the programmed cell death-1 (PD-1)/programmed cell death-ligand 1 (PD-L1) pathway with small molecules is a promising approach for cancer immunotherapy. Herein, novel small molecules compounds bearing various scaffolds including thiophene, thiazole, tetrahydroquinoline, benzimidazole and indazole were designed, synthesized and evaluated for their inhibitory activity against the PD-1/PD-L1 interaction. Among them, compound exhibited the most potent activity with IC of 189.6 nM in the homogeneous time-resolved fluorescence (HTRF) binding assay. Surface plasmon resonance (SPR) assay demonstrated that bound to PD-L1 with high affinity (K values of 231 nM and 311 nM for hPD-L1 and mPD-L1, respectively). In the HepG2/Jurkat T co-culture cell model, decreased the viability rate of HepG2 cells in a concentration-dependent manner. In addition, showed significant antitumor efficacy (TGI = 52.6 % at 40 mg/kg) without obvious toxicity in the B16-F10 melanoma model. Furthermore, flow cytometry analysis demonstrated that inhibited tumor growth by activating the tumor immune microenvironment. These findings indicate that is a promising PD-1/PD-L1 inhibitor deserving further investigation.

中文翻译：

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发现 4-苯基-1H-吲唑衍生物作为针对 PD-1/PD-L1 相互作用的新型小分子抑制剂

用小分子抑制程序性细胞死亡-1 (PD-1)/程序性细胞死亡-配体 1 (PD-L1) 通路是一种有前景的癌症免疫治疗方法。在此，设计、合成了带有各种支架（包括噻吩、噻唑、四氢喹啉、苯并咪唑和吲唑）的新型小分子化合物，并评估了它们对 PD-1/PD-L1 相互作用的抑制活性。其中，化合物在均相时间分辨荧光 (HTRF) 结合测定中表现出最有效的活性，IC 为 189.6 nM。表面等离子共振 (SPR) 测定表明，它以高亲和力与 PD-L1 结合（hPD-L1 和 mPD-L1 的 K 值分别为 231 nM 和 311 nM）。在 HepG2/Jurkat T 共培养细胞模型中，HepG2 细胞的存活率以浓度依赖性方式降低。此外，在 B16-F10 黑色素瘤模型中显示出显着的抗肿瘤功效（40 mg/kg 时 TGI = 52.6%），且无明显毒性。此外，流式细胞术分析表明，它通过激活肿瘤免疫微环境来抑制肿瘤生长。这些发现表明这是一种有前途的 PD-1/PD-L1 抑制剂，值得进一步研究。