Discovery and optimization of novel 3-benzyl-N-phenyl-1H-pyrazole-5-carboxamides as bifunctional antidiabetic agents stimulating both insulin secretion and glucose uptake
Graphical abstract
Introduction
Type 2 diabetes mellitus (T2DM), which represents approximately 90% of all cases of diabetes [1], is characterized by persistent hyperglycemia caused by abnormalities in insulin action and β-cell function [2,3]. T2DM affected more than 400 million people worldwide in 2018 and this number is projected to rise to about 500 million by 2030 [4,5]. T2DM causes a series of dysfunctions in multiple organs and tissues and can result in severe chronic complications, such as end-stage renal disease, blindness, arterial disease, slow wound healing, and limb amputation [6]. Numerous therapeutic options for the treatment of T2DM have been developed but only a minority of patients achieve long-term glycaemic control [7,8].
One of the primary factors associated with the development of T2DM is a decrease in glucose-stimulated insulin secretion (GSIS) in pancreatic β-cells [9,10]. Sulfonylureas, which are commonly used oral insulinotropic agents in the clinical management of T2DM [11], increase insulin secretion from β-cells by closing K-ATP channels in the cell membrane. However, drugs in this class often elicit hypoglycemia because they continuously stimulate insulin secretion independently of blood glucose level [11]. In order to compensate for the major drawback of sulfonylureas, glucose-dependent insulin secretagogues, including dipeptidyl peptidase-4 (DPP-4) inhibitors and ligands that target islet G-protein-coupled receptors (GPCRs), have recently been developed [12]. Nonetheless, recent studies have suggested that DPP-4 inhibitors cause severe joint pain and glucagon-like peptide-1 (GLP-1) receptor agonists increase the risk of cholelithiasis [13,14]. Moreover, these agents may be associated with an increased risk of cholangiocarcinoma [15]. Continuous efforts for the development of improved therapies, such as G-protein-coupled receptor (GPR) 40 and GPR119 agonists, are ongoing to address the limitations of current treatments; however, these options are still not clinically available [16,17]. The identification of novel molecules and pathways that have the potential to correct glycaemia via the stimulation of GSIS is, therefore, highly desirable.
In an effort to discover novel antidiabetic agents, an in-house chemical library containing approximately heterocycle-based 500 compounds was screened using INS-1 cells with a GSIS assay. The INS-1 cell line has been widely used for studies of glucose-dependent β-cell function because it secretes insulin in response to concentrations of glucose within the physiological range [18]. From the preliminary screening, we identified hit compound 1 which exhibited a strong insulin secretion activity, equal to that of a representative sulfonylurea gliclazide, at a concentration of 10 μM (Fig. 1A). Interestingly, compound 1 consists of a core 5-carboxamidopyrazole and two para-halo-substituted benzene rings and has relatively good lead-like properties (MW ≤ 460, rings ≤ 4, hydrogen-bond donors ≤ 5, hydrogen-bond acceptors ≤ 9, and −4 ≤ LogP ≤ 4.2) [19]. Herein, we designed and synthesized a new set of 3-benzyl-N-phenyl-1H-pyrazole-5-carboxamides by decorating various substituents on both benzene rings (Fig. 1B). Furthermore, we attempted to optimize our analogues in detail and establish a brief structure-activity relationship (SAR).
Section snippets
Chemistry
Based on the structure of hit 1, we initially decided to introduce various substituents on the para positions of both benzene rings. The synthetic route for the final analogues 1 and 6–22 is illustrated in Scheme 1. The commercially available phenylacetones 2a–c were first condensed with diethyl oxalate in the presence of t-BuOK, followed by a second condensation of the resulting 2,4-dioxopentanoates 3a–c with hydrazine under acidic conditions to afford the desired pyrazoles 4a–c. The key
Conclusions
In summary, a novel series of 3-benzyl-N-phenyl-1H-pyrazole-5-carboxamides was synthesized and evaluated for their glucose-stimulated insulin secretion activity in INS-1 cell line. The newly synthesized 41 analogues were screened for their cytotoxicity against β-cells to ensure pharmaceutical safety. Stepwise SAR-based optimization led to the discovery of compound 26, which potently increased GSIS from β-cells without cytotoxicity. Western blot assay showed that 26 could augment GSIS via the
Chemistry
Unless noted otherwise, all starting materials and reagents were obtained from commercial suppliers and were used without further purification. Reaction flasks were dried at 100 °C. Air- and moisture-sensitive reactions were performed under an argon atmosphere. All solvents used for routine isolation of products and chromatography were reagent-grade. Flash column chromatography was performed using silica gel 60 (230–400 mesh, Merck) with the indicated solvents. Thin-layer chromatography was
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgments
This research was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (NRF-2018R1D1A1B07045101).
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These authors contributed equally to this work.