Enpp-1-IN-20 (Compound 31) is an ectonucleotide pyrophosphatase/phosphodiesterase 1 ( ENPP1 ) inhibitor, with an IC 50 of 0.09 nM. Enpp-1-IN-20 has strongest inhibitory activity in the cell-based assay, with an IC 50 of 8.8 nM. Enpp-1-IN-20 has significant potency in both ENPP1 inhibition and STING pathway stimulation in vitro. Enpp-1-IN-20 can be used for the research of cancer.