Introduction: CD73 and adenosine support growth-promoting neovascularization, metastasis, and survival in cells, and promote anti-PD-1 mAb therapy-induced immune escape. Consequently, developing a CD73 inhibitor as monotherapy and a potential beneficial combination partner with immune-checkpoint inhibitors needs investigation.
Methods: CD73 inhibitors were evaluated in vitro with soluble and membrane-bound CD73 enzymes, as well as its PD biomarker responses in human peripheral blood mononuclear cells (PBMC) by flow cytometry and ELISA. The binding modes of the molecules were analyzed via molecular modeling. The anti-tumor activity and synergistic effect of SHR170008 in combination with anti-PD-1 mAb were evaluated in a syngeneic mouse breast cancer model.
Results: SHR170008 was discovered during the initial structural modifications on the link between the ribose and the α-phosphate of AMPCP, which significantly improved the stability of the compound confirmed by the metabolite identification study. Further modifications on the adenine base of AMPCP improved the potency due to forming stronger interactions with CD73 protein. It exhibited potent inhibitory activities on soluble and endogenous membrane-bound CD73 enzymes, and induced IFNγ production, reversed AMP-suppressed CD25⁺ and CD8⁺/CD25⁺ expression, and enhanced granzyme B production on CD8⁺ T cells in human PBMC. SHR170008 showed dose-dependent anti-tumor efficacy with suppression of adenosine in the tumors in EMT6 mouse breast tumor model. The increase of adenosine in tumor tissue by anti-PD-1 mAb alone was suppressed by SHR170008 in the combination groups. Simultaneous inhibition of CD73 and PD-1 neutralization synergistically enhanced antitumor immunity and biomarkers in response, and exposures of SHR170008 were correlated with the efficacy readouts.
Conclusion: Our findings suggest that CD73 may serve as an immune checkpoint by generating adenosine, which suppresses the antitumor activity of anti-PD-1 mAb, and inhibition of CD73 may be a potential beneficial combination partner with immune-checkpoint inhibitors to improve their therapeutic outcomes in general.

Keywords: small-molecule inhibitor of CD73, adenosine, anti-PD-1 mAb, checkpoint blockade, immunotherapy, combination therapy


中文翻译：

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一种新型 CD73 抑制剂 SHR170008 在乳腺癌小鼠模型中通过 PD-1 阻断抑制肿瘤中的腺苷并增强抗肿瘤活性

简介： CD73 和腺苷支持细胞中促进生长的新血管形成、转移和存活，并促进抗 PD-1 mAb 治疗诱导的免疫逃逸。因此，需要研究开发一种 CD73 抑制剂作为单一疗法以及与免疫检查点抑制剂的潜在有益组合伙伴。
方法：通过流式细胞术和 ELISA 在体外评估 CD73 抑制剂与可溶性和膜结合 CD73 酶，以及其在人外周血单个核细胞 (PBMC) 中的 PD 生物标志物反应。通过分子建模分析分子的结合模式。在同基因小鼠乳腺癌模型中评估了 SHR170008 与抗 PD-1 mAb 联合的抗肿瘤活性和协同作用。
结果：SHR170008是在对AMPCP的核糖和α-磷酸之间的联系进行初步结构修饰期间发现的，这显着提高了代谢物鉴定研究证实的化合物的稳定性。由于与 CD73 蛋白形成更强的相互作用，对 AMPCP 腺嘌呤碱基的进一步修饰提高了效力。它对可溶性和内源性膜结合 CD73 酶表现出强效抑制活性，并诱导 IFNγ 产生，逆转 AMP 抑制的 CD25 ⁺和 CD8 ⁺ /CD25 ⁺表达，并增强 CD8 ^{+上颗粒酶 B 的产生}人 PBMC 中的 T 细胞。SHR170008 在 EMT6 小鼠乳腺肿瘤模型中显示出剂量依赖性抗肿瘤功效，抑制肿瘤中的腺苷。在联合组中，SHR170008 抑制了单独抗 PD-1 mAb 对肿瘤组织中腺苷的增加。同时抑制 CD73 和 PD-1 中和可协同增强抗肿瘤免疫和响应生物标志物，SHR170008 的暴露与疗效读数相关。
结论：我们的研究结果表明，CD73 可能通过产生腺苷作为免疫检查点，从而抑制抗 PD-1 mAb 的抗肿瘤活性，抑制 CD73 可能是与免疫检查点抑制剂的潜在有益组合，以提高其治疗效果。一般的结果。

关键词：CD73小分子抑制剂、腺苷、抗PD-1单克隆抗体、检查点阻断、免疫治疗、联合治疗