KR-66223 is a novel dipeptidyl peptidase-4 (DPP-4) inhibitor that is under development for the treatment of type 2 diabetes. We studied the pharmacokinetic and pharmacodynamic characteristics of KR-66223 in rats, monkeys, and dogs to predict PK/PD profiles in humans. KR-66223 exhibited a moderate volume of distribution (0.3-1.8 L/kg), moderate systemic clearance (1-1.76 L/h/kg), long half-life (>3 h), and low oral bioavailability (below 2.5% in all tested species). The EC(50)s for DPP-4 inhibition as calculated by the E(max) model was below 4.25 ng/mL across all species, confirming KR-66223 as a potent DPP-4 inhibitor. In vitro plasma protein binding suggested that it was available (69-89%), correlating with its volume of distribution in animals. Using allometric scaling and the E(max) model, human systemic clearance, volume of the central compartment, volume of the peripheral compartment, and EC₅₀ for DPP-4 inhibition were predicted to be 0.31 L/h/kg, 0.1 L/kg, 2.4 L/kg, and 3 ng/mL, respectively. These results can serve as a valuable foundation for future clinical trials.