RBx-0597, a potent, selective and slow-binding inhibitor of dipeptidyl peptidase-IV for the treatment of type 2 diabetes

Dipeptidyl peptidase IV (DPP-IV) inhibiton is a well recognized approach to treat Type 2 diabetes. RBx-0597 is a novel DPP-IV inhibitor discovered in our laboratory. The aim of the present study was to characterize the pharmacological profiles of RBx-0597 in vitro and in vivo as an anti-diabetic agent. RBx-0597 inhibited human, mouse and rat plasma DPP-IV activity with IC50 values of 32, 31 and 39 nM respectively. RBx-0597 exhibited significant selectivity over dipeptidyl peptidase8 (DPP-8), dipeptidyl peptidase9 (DPP-9) (150–300 fold) and other proline-specific proteases (> 200–2000 fold). Kinetic analysis revealed that RBx-0597 is a competitive and slow binding DPP-IV inhibitor. In ob/ob mice, RBx-0597 (10 mg/kg) inhibited plasma DPP-IV activity upto 50% 8 h post-dose and showed a dose-dependent glucose excursion. RBx-0597 (10 mg/kg) showed a significant glucose lowering effect (∼ 25% AUC of △ blood glucose) which was sustained till 12 h, significantly increased the active glucagon-like peptide-1(GLP-1) and insulin levels. It showed a favourable pharmacokinetic profile (plasma clearance:174 ml/min/kg; Cmax 292 ng/ml; T1/2 0.28 h; Tmax 0.75 h and Vss 4.13 L/kg) in Wistar rats with the oral bioavailability (Foral) of 65%. In summary, the present studies indicate that RBx-0597 is a novel DPP-IV inhibitor with anti-hyperglycemic effect and a promising candidate for further development as a drug for the treatment of type 2 diabetes.