Blockade of the programmed cell death-1 (PD-1)/programmed cell death-ligand 1 (PD-L1) signalling pathway is a promising tumour immunotherapeutic approach, and small molecule drugs have more advantages than monoclonal antibody macromolecules in clinical applications. Therefore, a series of 1-methyl-1H-pyrazolo[4,3-b]pyridine derivatives as PD-1/PD-L1 interaction novel small-molecule inhibitors were designed employing a ring fusion strategy. The inhibitory activity of compounds was evaluated by the HTRF assay, among which D38 was identified as the most potent PD-1/PD-L1 interaction inhibitor with an IC₅₀ value of 9.6 nM. Furthermore, D38 exhibited prominent inhibitory activity against the PD-1/PD-L1 interaction with an EC₅₀ value of 1.61 μM in a coculture model of PD-L1/TCR activator-expressing CHO cells and PD-1-expressing Jurkat cells. In addition, the preliminary structure-activity relationships (SARs) of compounds were elucidated, and the binding mode of D38 with the PD-L1 dimer was analysed by molecular docking. Overall, D38 could be employed as a prospective lead compound of PD-1/PD-L1 interaction inhibitors for further development.

阻断程序性细胞死亡-1（PD-1）/程序性细胞死亡-配体1（PD-L1）信号通路是一种很有前景的肿瘤免疫治疗方法，小分子药物在临床应用中比单克隆抗体大分子更具优势。因此，采用环融合策略设计了一系列1-甲基-1H-吡唑并[ 4,3-b ]吡啶衍生物作为PD-1/PD-L1相互作用的新型小分子抑制剂。通过HTRF测定评估化合物的抑制活性，其中D38被鉴定为最有效的PD-1/PD-L1相互作用抑制剂，IC ₅₀值为9.6 nM。此外，D38对 PD-1/PD-L1 与 EC 相互作用表现出显着的抑制活性。在表达 PD-L1/TCR 激活剂的 CHO 细胞和表达 PD-1 的 Jurkat 细胞的共培养模型中，₅₀值为 1.61 μM。此外，阐明了化合物的初步构效关系（SARs），并通过分子对接分析了D38与PD-L1二聚体的结合模式。总体而言，D38可用作 PD-1/PD-L1 相互作用抑制剂的前瞻性先导化合物，用于进一步开发。