We report on the identification of 2-({6-[(3R)-3-amino-3-methylpiperidine-1-yl]-1, 3-dimethyl- 2, 4-dioxo-1, 2, 3, 4-tetrahydro-5H-pyrrolo [3, 2-d] pyrimidine-5-yl} methyl)-4- fluorobenzonitrile (DSR-12727)(7a) as a potent and orally active DPP-4 inhibitor without mechanism-based inactivation of CYP3A. Compound 7a showed good DPP-4 inhibitory activity (IC50= 1.1 nM), excellent selectivity against related peptidases and other off- ...