Cancer cells initiate an innate immune response by synthesizing and exporting the small molecule immunotransmitter cGAMP, which activates the anti-cancer Stimulator of Interferon Genes (STING) pathway in the host. An extracellular enzyme, ectonucleotide pyrophosphatase phosphodiesterase 1 (ENPP1), hydrolyzes cGAMP and negatively regulates this anti-cancer immune response. Small molecule ENPP1 inhibitors are much needed as tools to study basic biology of extracellular cGAMP and as investigational cancer immunotherapy drugs. Here, we surveyed structure-activity relationships around a series of cell-impermeable and thus extracellular-targeting phosphonate inhibitors of ENPP1. Additionally, we solved the crystal structure of an exemplary phosphonate inhibitor to elucidate the interactions that drive potency. This study yielded several best-in-class compounds with Ki < 2 nM and excellent physicochemical and pharmacokinetic properties. Finally, we demonstrate that an ENPP1 inhibitor delays tumor growth in a breast cancer mouse model. Together, we have developed ENPP1 inhibitors that are excellent tool compounds and potential therapeutics.

中文翻译：

---

ENPP1小分子抑制剂（免疫递质cGAMP的细胞外磷酸二酯酶）的结构辅助开发

癌细胞通过合成和输出小分子免疫递质cGAMP来启动先天免疫应答，后者激活宿主体内干扰素基因（STING）途径的抗癌刺激物。一种细胞外酶，外核苷酸焦磷酸酶磷酸二酯酶1（ENPP1），水解cGAMP并负面调节这种抗癌免疫反应。小分子ENPP1抑制剂作为研究细胞外cGAMP基础生物学的工具和研究性癌症免疫治疗药物非常需要。在这里，我们调查了一系列的细胞不可渗透，因此针对细胞外靶向的ENPP1膦酸酯抑制剂周围的结构活性关系。另外，我们解决了示例性膦酸酯抑制剂的晶体结构，以阐明驱动效力的相互作用。这项研究产生了Ki <2 nM，具有出色的理化和药代动力学特性的几种同类最佳化合物。最后，我们证明了ENPP1抑制剂可延迟乳腺癌小鼠模型中的肿瘤生长。我们共同开发了ENPP1抑制剂，它们是出色的工具化合物和潜在的治疗方法。