Compounds, compositions and methods are provided for the inhibition of ENPP1. Aspects of the subject methods include contacting a sample with a ENPP1 inhibitor to inhibit cGAMP hydrolysis activity of ENPP1. In some cases, the ENPP1 inhibitor is cell impermeable. Also provided are compositions and methods for treating cancer. Aspects of the methods include administering to a subject a therapeutically effective amount of a ENPP1 inhibitor to treat the subject for cancer. In certain cases, the cancer is a solid tumor cancer. Also provided are methods of administering radiation therapy to a subject either before or after administering an ENPP1 inhibitor. The radiation therapy can be administered at a dosage and/or frequency effective to reduce radiation damage to the subject. In certain cases, the method is performed in combination with a chemotherapeutic agent, or a checkpoint inhibitor, or both.
