The PK and the tissue distribution profiles of k

The PK and the tissue distribution profiles of 15k, 15j, 14d and 2 (Table 8) in male ICR mice were assessed. 15k, 15j, 14d all exhibited prolonged half-lives and improved plasma exposure. 15k achieved the highest concentration (15.45 μg/mL) in plasma among four compounds. The observation that 15j (S,S-isomers) and 15k (S,R-isomers) differed substantially in peak times and peak plasma concentrations indicated that the stereochemistry of the tail significantly affected absorption. Compared with 2, 15k had 5.4-fold, 4.1-fold and 15.5-fold improvement in plasma exposure, half-life time and AUC (area under the curve), respectively. Tissue distribution assays showed that 14d, 15j and 15k had much lower CNS exposure (B/P = 0.018, 0.006 and 0.011 respectively) than 2. We also examined the distribution of compounds to the liver, based on the report that TAK-875 had 3 times higher distribution to the liver than to plasma [35]. 15j and 15k displayed lower L/P compared with 2. However, 14d was not studied any further because of safety concerns associated with its 15-times higher distribution to the liver than to plasma. 15k, with promising PK and safety profiles, was progressed to in vivo efficacy studies, where it demonstrated a significant decrease (P < 0.001) in blood glucose level following a 2.5 g/kg oral glucose load in the oral glucose tolerated test (OGTT) (Fig. 4).
Conclusion We developed a series of amide derivatives driven by the moderate CNS exposure, high in vitro clearance and limited oral exposure of 2. By inserting a carbonyl at the position prone to N-dealkylation metabolism and opening up the indene, as well as introducing a nitrogen atom to reduce LogP and elevate tPSA, we obtained 13c with improved physicochemical properties and liver microsomal stability. Further SAR research and optimization yielded 15k, which exhibited the best in vitro activity, excellent permeability and markedly improved in vitro stability. Furthermore, studies demonstrated that 15k possessed superior PK properties in vivo, lower distribution to brain and liver than to plasma compared with LY2881835, supporting that 15k is more likely to avoid the undesired effects in the CNS and liver. In conclusion, our results disclosed an orally efficacious compound 15k, which represents a promising lead compound for developing a safe antidiabetic drug that acts via activation of GPR40.
Experimental section
Abbreviations AUC, area under curve; BBB, brain-blood-barrier; (BOC)2O, di-tert-butyl-dicarbonate; B/P, total brain-to-plasma drug distribution ratio; CCl4, carbon tetrachloride; CL, clearance; CNS, central nervous system; Cmax, maximum plasma concentration; DCM, dichloromethane; DIPEA, N-diisopropylethylamine; DMAP, 4-dimethylaminopyridine; DMF, N,N-dimethylformadide; DMSO, dimethylsulfoxide; FFAR1, free fatty ubiquitin conjugating enzyme receptor 1; FFAs, free fatty acids; FLIPR, Fluorometric Imaging Plate Reader; GLP-1, glucagon like peptide 1; GPR40, G-protein coupled receptor 40; HATU, 1-[Bis(dimethylamino)methylene]-1H-1,2,3-triazolo[4,5-b]pyridinium 3-oxid hexafluorophosphate; HPLC, High Performance Liquid Chromatography; ICR mice, Institute of Cancer Research mice; L/P, liver-to-plasma drug distribution ratio; NADPH, Nicotinamide Adenine Dinucleotide Phosphate; NBS, Nbromosuccinimide; PK, pharmacokinetic; SAR, structure-activity relationship; T, half-life time; T2DM, type 2 diabetes mellitus; tPSA, total polar surface area.
Author contribution
Declaration of interest
Acknowledgements This work was supported by National Natural Science Foundation of China (Grants 81473093) and State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica (SIMM1601ZZ-02).
Type 2 diabetes mellitus (T2DM) is a disease characterized by defects in insulin secretion from pancreatic β-cells and/or insulin resistance in target tissues of insulin., , Insulin secretagogues, such as sulfonylureas and glinides are commonly used to stimulate insulin secretion in diabetic patients. However, these drugs promote insulin secretion independent of blood glucose levels, thereby leading to the risk of hypoglycemia., GPR40 (also known as FFAR1) is a novel G protein-coupled receptor (GPCR) that is expressed in pancreatic β-cells and responds to free-fatty acid (FFA) concentrations. Activation of GPR40 potentiates glucose-stimulated insulin secretion and lowers plasma glucose concentrations in multiple animal models of insulin resistance and obesity., , Because GPR40 mediated insulin secretion is glucose-dependent, it is believed that pharmacologic activation of the receptor should not induce hypoglycemia in either fed or fasted states. Consequently, a GPR40 agonist has potential to be a safe and effective alternative to currently available therapies for T2DM., , Therapeutic efficacy has been demonstrated in several clinical trials targeting the GPR40 pathway, for example, LY-2881835 (entered Phase I clinical trial), JTT-851 (entered Phase II clinical trial, structure not disclosed) and TAK-875 (entered Phase III clinical trial).We previously described the development of the GPR40 agonist AMG 837 from a series of beta-substituted propionic acids, which were identified in a high-throughput screen. In multiple animal models, AMG 837 enhances glucose-stimulated insulin secretion and lowers plasma glucose levels. Because GPR40 activity is glucose-dependent, AMG 837 did not induce hypoglycemia in any of the models tested. Encouraged by these results, we initiated a Phase I clinical trial of AMG 837.While the clinical evaluation of AMG 837 was ongoing, we turned our attention to the development of a structurally distinct GPR40 agonist. Although AMG 837 is a carboxylic acid, its physicochemical properties, including low polar surface area (tPSA 47, ), suggest a reasonable possibility of achieving CNS exposure. Additional support comes from a structurally close analog of AMG 837 (with 4′-chloro-2′-ethoxy-(1,1′-biphenyl)-4-yl replacing 4′-(trifluoromethyl)-(1,1′-biphenyl)-3-yl of AMG 837) which showed a brain to plasma ratio of 0.6 3h after an oral dose of 5mg/kg in rats. Given that the efficacy of GPR40 agonists is derived peripherally and that they are likely to be dosed chronically, we sought molecules with minimal brain penetration. In general, increasing the polar surface area (PSA) of a molecule tends to decrease its blood–brain barrier permeability. In keeping with this principle, we focused on increasing the PSA of AMG 837, while maintaining its potency and metabolic stability. The approach taken was to introduce polar groups to the tail group and/or the head group of the AMG 837 class of GPR40 agonists.