– T3Inh-1 is a potent and selective inhibitor of ppGalNAc-T3 (IC50=7 ?M). T3Inh-1 reduces FGF23 hormone levels in both tissue cells and mice, without causing any toxic side effects. T3Inh-1 also prevents breast cancer cells. The enzyme ppGalNAc-T3 is implicated in at least two medically important pathways: cancer metastasis and stabilization of FGF23 (regulates phosphate levels in the bloodstream).