WT and Pahenu2 mice, a widely used mouse model of PKU, displayed dose-dependent aminoaciduria upon treatment with JN-170, including increased urinary excretion of Phe, confirming that pharmacological inhibition of SLC6A19 phenocopies the loss-of-function phenotype observed in Slc6a19-KO mice as well as in humans with Hartnup disorder, which results from mutations in SLC6A19. Here, SLC6A19 is linked to Hartnup disease.