{Reference Type}: Journal Article {Title}: [1,2,4]Triazolo[1,5-a]pyrimidine derivatives: Structure-activity relationship study leading to highly selective ENPP1 inhibitors. {Author}: Kawaguchi M;Minami S;Ieda N;Nakagawa H; {Journal}: Bioorg Med Chem Lett {Volume}: 110 {Issue}: 0 {Year}: 2024 Sep 15 {Factor}: 2.94 {DOI}: 10.1016/j.bmcl.2024.129820 {Abstract}: The STING (stimulator of interferon genes) pathway is one of the pathways that regulate innate immunity, and the extracellular hydrolytic enzyme ecto-nucleotide pyrophosphatase/phosphodiesterase 1 (ENPP1) has been identified as its dominant negative regulator. Since activation of the innate immune system is a promising strategy for the treatment of various infectious diseases and cancers, ENPP1 inhibitors have attracted great attention as candidate drugs. We have previously identified small-molecule ENPP1 inhibitors having a [1,2,4]triazolo[1,5-a]pyrimidine scaffold by means of chemical screening using a fluorescence probe, TG-mAMP. In this study, we evaluated the structure-activity relationships of the hit and lead compounds in detail, and succeeded in developing compounds that strongly and selectively inhibit ENPP1 not only in vitro, but also in cellular systems.