Pharmacological activation of stimulator of interferon genes (STING) by agonists has emerged as a new modality of cancer immunotherapy. However, current available STING agonists remain in early developmental stage or failed in clinic trials due to limited efficacy in humans. In this report, we performed a structure−activity relationship study based on the benzothiophene oxobutanoic acid scaffold of MSA-2, a well-documented STING agonist by Merck, leading to a series of N-substituted acyloxyamino derivatives with potent STING activating effect. Among them, compounds 57 and 60 displayed the most potent activity specifically targeting both h- and m-STING. Particularly, 57 displayed more potent and rapid activation of the STING signaling pathway than ADU-S100 in THP1-Dual cells. In vivo anti-tumor efficacy of 57 by intratumoral or oral administration was also demonstrated in several mouse tumor models. Intriguingly, treatment with 57 eradicated all the CT26 tumor without further recurrence in all treated mice, which could also reject the same tumor re-inoculation, indicating an induction of immune memory by 57. Taken together, acyloxyamino derivative 57 represents a new chemotype of STING agonist with well-demonstrated in vivo anti-tumor activity, which is deserved for further investigation.

激动剂对干扰素基因刺激物 (STING) 的药理激活已成为癌症免疫治疗的一种新方式。然而，目前可用的 STING 激动剂仍处于早期发育阶段或由于对人体的疗效有限而在临床试验中失败。在本报告中，我们基于 MSA-2 的苯并噻吩氧代丁酸支架进行了结构-活性关系研究，MSA-2 是 Merck 有充分记录的 STING 激动剂，产生了一系列具有有效 STING 活化作用的N-取代酰氧基氨基衍生物。其中，化合物57和60表现出最有效的活性，专门针对 h-和 m-STING。特别是57在 THP1-Dual 细胞中显示出比 ADU-S100 更有效和更快速地激活 STING 信号通路。57通过瘤内或口服给药的体内抗肿瘤功效也在几种小鼠肿瘤模型中得到证实。有趣的是，用57治疗根除所有 CT26 肿瘤，在所有治疗的小鼠中没有进一步复发，这也可以拒绝相同的肿瘤重新接种，表明57诱导了免疫记忆。总之，酰氧基氨基衍生物57代表了一种新的 STING 激动剂化学型，具有良好的体内抗肿瘤活性，值得进一步研究。