Sitagliptin

Sitagliptin (MK-0431) is an orally active and highly selective DPP4 inhibitor with an IC₅₀ value of 19 nM. Sitagliptin blocks the degradation of glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic peptide (GIP) by competing inhibition mechanism (Kᵢ = 1 nM), thereby increasing the level of active incretin. Sitagliptin can also directly stimulate the secretion of GLP-1 by intestinal L cells by activating the cAMP/PKA and ERK1/2 pathways, and this effect is independent of DPP-4. Sitagliptin shows protective effects on pancreatic islet grafts in 1-type diabetes models. Sitagliptin can be used for the study of 1-type and 2-type diabetes^{[1][2][3][4][5]}. IC50 & Target:IC50: 19 nM (DPP4)^[1] In Vitro:Sitagliptin phosphate exhibits a potent inhibitory effect on DPP-4 with IC₅₀ of 19 nM from Caco-2 cell extracts^[1]. Sitagliptin reduces in vitro migration of isolated splenic CD4 T-cells through a pathway involving cAMP/PKA/Rac1 activation^[2]. Stagliptin exerts a novel, direct action in order to stimulate GLP-1 secretion by the intestinal L cell through a DPP-4-independent, protein kinase A- and MEK-ERK1/2-dependent pathway. It reduces the effect of autoimmunity on graft survival^[3]. In Vivo:In vivo, the ED₅₀ value of sitagliptin phosphate for inhibition of plasma DPP-4 activity is calculated to be 2.3 mg/kg 7 hour postdose and 30 mg/kg 24 hour postdose in freely fed Han-Wistar rats^[1]. The streptozotocin-induced type 1 diabetes mouse model exhibits elevated DPP-4 levels in the plasma that can be substantially inhibited in mice on an Sitagliptin phosphate diet. This is achieved by a positive effect on the regulation of hyperglycemia, potentially through prolongation of islet graft survival^[4]. The plasma clearance and volume of distribution of Sitagliptin phosphate are higher in rats (40-48 mL/min/kg, 7-9 L/kg) than in dogs (9 mL/min/kg, 3 L/kg); and its half-life is shorter in rats,2 hours compared with 4 hours in dogs^[5].