The activation of stimulator of interferon genes (STING) signaling pathways plays an important role in the innate immune response. Although several STING agonists have been developed recently, the majority of clinical CDN STING agonists are administered by intratumoral (IT) injection. Therefore, there remains a need to develop diverse non-CDN small-molecule STING agonists with systemic administration. Herein, by using a scaffold hopping strategy, we designed a series of thieno [2,3-d]imidazole derivatives as novel STING agonists. Further structure-activity relationship study and optimization led to the discovery of compound 45 as a highly potent human STING agonist with an EC₅₀ value of 1.2 nM. Compound 45 was found to bind to multiple human STING isoforms and accordingly activated the downstream TBK1/IRF3 and NF-κB signaling pathways in the reporter cells bearing with different STING isoforms. The activation on STING signaling pathway was abolished in the STING knock-out cells, indicating that it is a specific STING agonist. Compound 45 significantly inhibited the tumor growth in allograft 4T1 and CT26 tumor models by systemic administration, and more significantly, 45 was able to induce tumor regression in CT26 tumor model without inducing weight loss, suggesting that compound 45 is a highly promising candidate worthy for further development.

干扰素基因刺激物（STING）信号通路的激活在先天免疫反应中起重要作用。尽管最近开发了几种 STING 激动剂，但大多数临床 CDN STING 激动剂是通过瘤内 (IT) 注射给药的。因此，仍然需要开发多种全身给药的非 CDN 小分子 STING 激动剂。在此，通过使用支架跳跃策略，我们设计了一系列噻吩并 [2,3-d] 咪唑衍生物作为新型 STING 激动剂。进一步的构效关系研究和优化导致发现化合物45是一种高效的人类 STING 激动剂，EC ₅₀值为 1.2 nM。化合物45发现与多种人类 STING 同种型结合，并因此激活带有不同 STING 同种型的报告细胞中的下游 TBK1/IRF3 和 NF-κB 信号通路。STING敲除细胞中STING信号通路的激活被消除，表明它是一种特异性的STING激动剂。化合物45通过全身给药显着抑制同种异体移植物 4T1 和 CT26 肿瘤模型中的肿瘤生长，更显着的是，45能够在 CT26 肿瘤模型中诱导肿瘤消退而不引起体重减轻，这表明化合物45是一种非常有前途的候选物，值得进一步研究发展。