ASP4000, a slow-binding dipeptidyl peptidase 4 inhibitor, has antihyperglycemic activity of long duration in Zucker fatty rats

ASP4000 ((2S)-1-{(1R,3S,4S,6R)-6-hydroxy-2-azabicyclo2.2.1]hept-3-yl]carbonyl}-2-pyrrolidinecarbonitrile hydrochloride) is a novel, potent and selective dipeptidyl peptidase 4 (DPP IV, EC 3.4.14.5) inhibitor (Keiko Tanaka-Amino et al. in Eur J pharmacol 59:444–449, 2008). The aim of the present study was to characterize the kinetic profile of and identify the long duration effect of the antihyperglycemic activity of ASP4000. ASP4000 was found to inhibit human recombinant DPP4 activity with a K _i of 1.05 nM, a k _on value of 22.3 × 10⁵ M⁻¹ s⁻¹, and a k _off of 2.35 × 10⁻³ M⁻¹ s⁻¹, with higher affinity than that of vildagliptin. The kinetic studies indicate that both the formation and dissociation of ASP4000/DPP4 complex were faster than those of vildagliptin, and that ASP4000 slow-bindingly inhibits DPP4 with a different mode of inhibition than vildagliptin. In addition, ASP4000 augmented the insulin response and ameliorated the glucose excursion during the oral glucose tolerance test in Zucker fatty rats at 4 h post dosing. ASP4000 is expected to be a promising, long duration DPP4 inhibitor for type 2 diabetes.