Identification of 5,7-Dihydro-6H-pyrrolo[2,3-d]pyrimidin-6-one Derivatives as ENPP1 Inhibitors for STING Pathway-Mediated Immunotherapy

A novel small-molecule ENPP1 inhibitor, compound 31 featuring a pyrrolopyrimidinone core, was identified. Compound 31 exhibited potent ENPP1 inhibition with an IC₅₀ of 14.68 nM and effectively activated the STING pathway in cell lines. In addition, 31 promoted cytokine release, thereby enhancing innate immune response. Moreover, 31 demonstrated favorable ADMET properties. Compound 31 displayed significant antitumor efficacy in 4T1 and CT26 syngeneic mouse models without notable toxicity. These findings highlight the potential of 31 as a promising compound for cancer immunotherapy by enhancing STING-mediated immune activation and improving responses to immune checkpoint inhibitors.