Design,synthesis, and effects of novel phenylpyrimidines as glucagon receptor antagonists

The hormone glucagon increases blood glucose levels through increasing hepatic glucose output. In diabetic patients, dysregulation of glucagon secretion contributes to hyperglycemia. Thus, the inhibition of glucagon receptor is one target for the treatment of hyperglycemia in type 2 diabetes. Here we designed and synthesized a series of small molecules based on phenylpyrimidine. Of these, the compound (R)-7a most significantly decreased the glucagon-induced cAMP production and glucagon-induced glucose production during in vitro and in vivo assays. In addition, (R)-7a showed good efficacy in glucagon challenge tests and lowered blood glucose levels in diabetic db/db mice. Our results suggest that the compound (R)-7a could be a potential glucose-lowering agent for treating type 2 diabetes.     

Design,synthesis, structure–activity relationships,and docking studies of pyrazole-containing derivatives as a novel series of potent glucagon receptor antagonists

Glucagon receptor antagonists possess a great potential for treatment of type 2 diabetes mellitus. A series of pyrazole-containing derivatives were designed, synthesized and evaluated by biological assays as glucagon receptor antagonists. Most of the compounds exhibited good in vitro efficacy. Two of them, compounds 17f and 17k, displayed relatively potent antagonist effects on glucagon receptors with IC₅₀ values of 3.9 and 3.6 μM, respectively. The possible binding modes of 17f and 17k with the cognate receptor were explored by molecular docking simulation.     

Identification of a novel conformationally constrained glucagon receptor antagonist

Identification of orally active, small molecule antagonists of the glucagon receptor represents a novel treatment paradigm for the management of type 2 diabetes mellitus. The present work discloses novel glucagon receptor antagonists, identified via conformational constraint of current existing literature antagonists. Optimization of lipophilic ligand efficiency (LLE or LipE) culminated in enantiomers (+)-trans-26 and (−)-trans-27 which exhibit good physicochemical and in vitro drug metabolism profiles. In vivo, significant pharmacokinetic differences were noted with the two enantiomers, which were primarily driven through differences in clearance rates. Enantioselective oxidation by cytochrome P450 was ruled out as a causative factor for pharmacokinetic differences.     

Discovery of novel, potent, selective, and orally active human glucagon receptor antagonists containing a pyrazole core

A novel class of 1,3,5-pyrazoles has been discovered as potent human glucagon receptor antagonists. Notably, compound 26 is orally bioavailable in several preclinical species and shows selectivity towards cardiac ion channels, other family B receptors such hGIP and hGLP1, and a large panel of enzymes and additional receptors. When dosed orally, compound 26 is efficacious in suppressing glucagon induced plasma glucose excursion in rhesus monkey and transgenic murine pharmacodynamic models at 1 and 10 mpk, respectively.     

Discovery of potent and orally bioavailable indazole-based glucagon receptor antagonists for the treatment of type 2 diabetes

Type 2 diabetes mellitus (T2DM) is characterized by chronically elevated plasma glucose levels. The inhibition of glucagon-induced hepatic glucose output via antagonism of the glucagon receptor (GCGR) using a small-molecule antagonist is a promising mechanism for improving glycemic control in the diabetic state. The present work discloses the discovery of indazole-based β-alanine derivatives as potent GCGR antagonists through an efficient enantioselective synthesis and structure-activity relationship (SAR) exploration and optimization. Compounds within this class exhibited excellent pharmacokinetic properties in multiple preclinical species. In an acute dog glucagon challenge test, compound 13K significantly inhibited glucagon-mediated blood glucose increase when dosed orally at 10 mg/kg.     

SAR-based optimization of 2-(1H-pyrazol-1-yl)-thiazole derivatives as highly potent EP1 receptor antagonists

We describe a medicinal chemistry approach for generating a series of 2-(1H-pyrazol-1-yl)thiazoles as EP₁ receptor antagonists. To improve the physicochemical properties of compound 1, we investigated its structure–activity relationships (SAR). Optimization of this lead compound provided small compound 25 which exhibited the best EP₁ receptor antagonist activity and a good SAR profile.     

Discovery of 1,2,3,4-tetrahydropyrimido[1,2-a]benzimidazoles as novel class of corticotropin releasing factor 1 receptor antagonists

A new class of corticotropin releasing factor 1 (CRF₁) receptor antagonists characterized by a tricyclic core ring was designed and synthesized. Novel tricyclic derivatives 2a–e were designed as CRF₁ receptor antagonists based on conformation analysis of our original 2-anilinobenzimidazole CRF₁ receptor antagonist. The synthesized tricyclic derivatives 2a–e showed CRF₁ receptor binding activity with IC₅₀ values of less than 400?nM, and the 1,2,3,4-tetrahydropyrimido-[1,2-a]benzimidazole derivative 2e was selected as a lead compound with potent in vitro CRF₁ receptor binding activity (IC₅₀?=?7.1?nM). To optimize the pharmacokinetic profiles of lead compound 2e, we explored suitable substituents on the 1-position and 6-position, leading to the identification of compound 42c-R, which exhibited potent CRF₁ receptor binding activity (IC₅₀?=?58?nM) with good oral bioavailability (F?=?68% in rats). Compound 42c-R exhibited dose-dependent inhibition of [¹²⁵I]-CRF binding in the frontal cortex (5 and 10?mg/kg, p.o.) as well as suppression of locomotor activation induced by intracerebroventricular administration of CRF in rats (10?mg/kg, p.o.). These results suggest that compound 42c-R successfully binds CRF₁ receptors in the brain and exhibits the potential to be further examined for clinical studies.     

A novel series of 4-methyl substituted pyrazole derivatives as potent glucagon receptor antagonists: Design,synthesis and evaluation of biological activities

A novel series of 4-methyl substituted pyrazole derivatives were designed, synthesized and biologically evaluated as potent glucagon receptor (GCGR) antagonists. In this study, compounds 9q, 9r, 19d and 19e showed high GCGR binding (IC₅₀?=?0.09?μM, 0.06?μM, 0.07?μM and 0.08?μM, respectively) and cyclic-adenosine monophosphate (cAMP) activities (IC₅₀?=?0.22?μM, 0.26?μM, 0.44?μM and 0.46?μM, respectively) in cell-based assays. Most importantly, the docking experiment demonstrated that compound 9r formed extensive hydrophobic interactions with the receptor binding pocket, making it justifiable to further investigate the potential of becoming a GCGR antagonist.     

N-Glycan Remodeling on Glucagon Receptor Is an Effector of Nutrient Sensing by the Hexosamine Biosynthesis Pathway

Glucose homeostasis in mammals is dependent on the opposing actions of insulin and glucagon. The Golgi N-acetylglucosaminyltransferases encoded by Mgat1, Mgat2, Mgat4a/b/c, and Mgat5 modify the N-glycans on receptors and solute transporter, possibly adapting activities in response to the metabolic environment. Herein we report that Mgat5^−/− mice display diminished glycemic response to exogenous glucagon, together with increased insulin sensitivity. Glucagon receptor signaling and gluconeogenesis in Mgat5^−/− cultured hepatocytes was impaired. In HEK293 cells, signaling by ectopically expressed glucagon receptor was increased by Mgat5 expression and GlcNAc supplementation to UDP-GlcNAc, the donor substrate shared by Mgat branching enzymes. The mobility of glucagon receptor in primary hepatocytes was reduced by galectin-9 binding, and the strength of the interaction was dependent on Mgat5 and UDP-GlcNAc levels. Finally, oral GlcNAc supplementation rescued the glucagon response in Mgat5^−/− hepatocytes and mice, as well as glycolytic metabolites and UDP-GlcNAc levels in liver. Our results reveal that the hexosamine biosynthesis pathway and GlcNAc salvage contribute to glucose homeostasis through N-glycan branching on glucagon receptor.     

Hit-to-lead optimization of 2-(1H-pyrazol-1-yl)-thiazole derivatives as a novel class of EP1 receptor antagonists

We describe a medicinal chemistry approach to generate a series of 2-(1H-pyrazol-1-yl)thiazole compounds that act as selective EP₁ receptor antagonists. The obtained results suggest that compound 12 provides the best EP₁ receptor antagonist activity and demonstrates good oral pharmacokinetics.     

Discovery of N-sulfonyl-7-azaindoline derivatives as potent,orally available and selective M4 muscarinic acetylcholine receptor agonists

We designed and synthesized novel N-sulfonyl-7-azaindoline derivatives as selective M₄ muscarinic acetylcholine receptor agonists. Modification of the N-carbethoxy piperidine moiety of compound 2, an M₄ muscarinic acetylcholine receptor (mAChR)-preferring agonist, led to compound 1, a selective M₄ mAChR agonist. Compound 1 showed a highly selective M₄ mAChR agonistic activity with weak hERG inhibition in vitro. A pharmacokinetic study of compound 1 in vivo revealed good bioavailability and brain penetration in rats. Compound 1 reversed methamphetamine-induced locomotor hyperactivity in rats (1–10 mg/kg, po).     

Synthesis and biological evaluation of novel potent FFA1 agonists containing 2,3-dihydrobenzo[b][1,4]dioxine

FFA1 (free fatty acid receptor 1) has emerged as an attractive antidiabetic target due to its role in mediating the enhancement of glucose-stimulated insulin secretion in pancreatic β cells with a low risk of hypoglycemia. Many reported FFA1 agonists possessed somewhat pharmacokinetic and/or safety issues. Herein, we describe the identification of 2,3-dihydrobenzo[b][1,4]dioxine as a novel scaffold for FFA1 agonists. Comprehensive structure-activity relationship study based on this scaffold led to the discovery of (S)-3-(4-(((S)-7-(4-methoxyphenyl)-2,3-dihydrobenzo [b][1,4]dioxin-2-yl)methoxy) phenyl)hex-4-ynoic acid (26k), which displayed a potent FFA1 agonistic activity and good pharmacokinetic profiles. Subsequent in vivo studies demonstrated that compound 26k significantly improved the glucose tolerance in ICR mice. In summary, compound 26k is a promising drug candidate for further investigation.     

The Role of Glucagon in the Pathophysiology and Management of Diabetes

Objective: There is general recognition that insulin and glucagon are the main hormones involved in the pathophysiology of diabetes, but the role of glucagon in diabetes is complex and in some circumstances controversial. The increasing appreciation of the role of glucagon in currently used hypoglycemic agents and the ongoing development of glucagon-targeted therapies underscores glucagon's important contribution in optimizing diabetes management. The current review provides a background on glucagon physiology and pathophysiology and an update for investigators, endocrinologists, and other healthcare providers on glucagon-modulating therapies.Methods: A literature review was conducted utilizing published literature in PubMed and AccessMedicine including the years 1922–2015 using the following key words: glucagon, bihormonal, diabetes mellitus, glucagon antagonists, glucagon-targeted therapies.Results: Glucagon is a counterregulatory hormone that promotes hepatic glucose production, thus preventing hypoglycemia in normal physiology. In patients with diabetes mellitus, glucagon secretion may be unregulated, which contributes to problems with glucose homeostasis. Several of the most effective therapies for diabetes have been found to suppress glucagon secretion or action, which may contribute to their success. Additionally, glucagon-specific targeted therapies, such as glucagon receptor antagonists, are being studied at a basic and clinical level.Conclusion: Glucagon plays an important role in contributing to hyperglycemia in patients with diabetes. Utilizing hypoglycemic agents that decrease glucagon secretion or inhibit glucagon action can help improve glycemic control, making these agents a valuable resource in diabetes therapy.Abbreviations:cAMP = cyclic adenosine monophosphateDPP-4 = dipeptidyl peptidase 4GLP-1 = glucagon-like peptide 1GR^-/- = glucagon receptor knockoutGR-ASO = antisense oligonucleotides targeted against the glucagon receptorHbA1c = hemoglobin A1cHGP = hepatic glucose productionSGLT-2 = sodium-glucose cotrans-porter 2T1DM = type 1 diabetes mellitusT2DM = type 2 diabetes mellitus     

Design and synthesis of 1-(1-benzothiophen-7-yl)-1H-pyrazole,a novel series of G protein-coupled receptor 52 (GPR52) agonists

G-protein-coupled receptor 52 (GPR52) is classified as an orphan Gs-coupled G-protein-coupled receptor. GPR52 cancels dopamine D2 receptor signaling and activates dopamine D1/N-methyl-d-aspartate receptors via intracellular cAMP accumulation. Therefore, GPR52 agonists are expected to alleviate symptoms of psychotic disorders. A novel series of 1-(benzothiophen-7-yl)-1H-pyrazole as GPR52 agonists was designed and synthesized based on compound 1b. Compound 1b has been reported by our group as the first orally active GPR52 agonist, but high lipophilicity and poor aqueous solubility still remained as issues for candidate selection. To resolve these issues, replacement of the benzene ring at the 7-positon of compound 1b with heterocylic rings, such as pyrazole and pyridine, was greatly expected to reduce lipophilicity to levels for which calculated logD values were lower than that of compound 1b. While evaluating the pyrazole derivatives, introduction of a methyl substituent at the 3-position of the pyrazole ring led to increased GPR52 agonistic activity. Moreover, additional methyl substituent at the 5-position of the pyrazole and further introduction of hydroxy group to lower logD led to significant improvement of solubility while maintaining the activity. As a result, we identified 3-methyl-5-hydroxymethyl-1H-pyrazole derivative 17 (GPR52 EC₅₀?=?21?nM, E_max?=?103%, logD?=?2.21, Solubility at pH 6.8?=?21?μg/mL) with potent GPR52 agonistic activity and good solubility compared to compound 1b. Furthermore, this compound 17 dose-dependently suppressed methamphetamine-induced hyperlocomotion in mice.     

Identification of 2-(2′-fluoro-[1,1′-biphenyl]-2-yl)acetamide as a Sodium Valproate-like broad spectrum anti-epileptic drug candidate

By further optimizing compound A [2′-fluoro-N-methyl-[1,1′-biphenyl]-2-sulfonamide], we identified DSP-0565 [2-(2′-fluoro-[1,1′-biphenyl]-2-yl)acetamide, 17a] as a strong, broad-spectrum anti-epileptic drug (AED) candidate. Our efforts mainly focused on finding an alternative polar group for the sulfonamide in order to improve ADME profile of compound A including good metabolic stability and no reactive metabolic production. This led to the identification of biphenyl acetamide as a new scaffold for development of broad-spectrum AED candidates. DSP-0565 showed anti-convulsant activity in various models (scPTZ, MES, 6?Hz and amygdala kindling) with good safety margin, and was therefore selected as a clinical candidate.     

Synthesis and biological evaluation of C-glucosides with azulene rings as selective SGLT2 inhibitors for the treatment of type 2 diabetes mellitus: Discovery of YM543

Here, a series of C-glucosides with azulene rings in the aglycon moiety was synthesized and the inhibitory activities toward hSGLT1 and hSGLT2 were evaluated. Starting from the azulene derivative 7 which had relatively good SGLT2 inhibitory activity, compound 8a which has a 3-[(azulen-2-yl)methyl]phenyl group was identified as a lead compound for further optimization. Introduction of a phenolic hydroxyl group onto the central benzene ring afforded a potent and selective SGLT2 inhibitor 8e, which reduced blood glucose levels in a dose-dependent manner in rodent diabetic models. A mono choline salt of 8e (YM543) was selected as a clinical candidate for use in treating type 2 diabetes mellitus.     

Discovery of 4-ethoxy-7H-pyrrolo[2,3-d]pyrimidin-2-amines as potent,selective and orally bioavailable LRRK2 inhibitors

Inhibition of LRRK2 kinase activity with small molecules has emerged as a potential novel therapeutic treatment for Parkinson’s disease. Herein we disclose the discovery of a 4-ethoxy-7H-pyrrolo[2,3-d]pyrimidin-2-amine series as potent LRRK2 inhibitors identified through a kinase-focused set screening. Optimization of the physicochemical properties and kinase selectivity led to the discovery of compound 7, which exhibited potent in vitro inhibition of LRRK2 kinase activity, good physicochemical properties and kinase selectivity across the kinome. Moreover, compound 7 was able to penetrate into the CNS, and in vivo pharmacology studies revealed significant inhibition of Ser935 phosphorylation in the brain of both rats (30 and 100?mg/kg) and mice (45?mg/kg) following oral administration.     

Design,synthesis, in vivo,and in silico evaluation of new coumarin-1,2,4-oxadiazole hybrids as anticonvulsant agents

A novel series of coumarin-1,2,4-oxadiazole hybrids were designed, synthesized, and evaluated as anticonvulsant agents. The title compounds were easily synthesized from reaction of appropriate coumarins and 3-aryl-5-(chloromethyl)-1,2,4-oxadiazole derivatives. In vivo anticonvulsant activity of the synthesized compounds were determined using pentylenetetrazole (PTZ)- and maximal electroshock (MES)-induced seizures confirming that they were more effective against MES test than PTZ test. It should be noted that compounds 3b, 3c, and 3e showed the best activity in MES model which possessed drug-like properties with no neurotoxicity. Anticonvulsant activity of the most potent compound 3b was remarkably reduced after treatment with flumazenil which confirmed the participation of a benzodiazepine mechanism in the anticonvulsant activity. Also, docking study of compound 3b in the BZD-binding site of GABA_A receptor confirmed possible binding of 3b to the BZD receptors.     

The synthesis and structure–activity relationship of 4-benzimidazolyl-piperidinylcarbonyl-piperidine analogs as histamine H3 antagonists

A structure–activity relationship study of the lead piperazinylcarbonylpiperidine compound 3 resulted in the identification of 4-benzimidazolyl-piperidinylcarbonyl-piperidine 6h as a histamine-3 (H₃) receptor antagonist. Additional optimization of 6h led to the identification of compounds 11i–k with K_i ? 0.5 nM and good in vivo activity.     

Discovery and optimization of 1,7-disubstituted-2,2-dimethyl-2,3-dihydroquinazolin-4(1H)-ones as potent and selective PKCθ inhibitors

A high-throughput screening campaign helped us to identify an initial lead compound (1) as a protein kinase C-θ (PKCθ) inhibitor. Using the docking model of compound 1 bound to PKCθ as a model, structure-based drug design was employed and two regions were identified that could be explored for further optimization, i.e., (a) a hydrophilic region around Thr442, unique to PKC family, in the inner part of the hinge region, and (b) a lipophilic region at the forefront of the ethyl moiety. Optimization of the hinge binder led us to find 1,3-dihydro-2H-imidazo[4,5-b]pyridin-2-one as a potent and selective hinge binder, which resulted in the discovery of compound 5. Filling the lipophilic region with a suitable lipophilic substituent boosted PKCθ inhibitory activity and led to the identification of compound 10. The co-crystal structure of compound 10 bound to PKCθ confirmed that both the hydrophilic and lipophilic regions were fully utilized. Further optimization of compound 10 led us to compound 14, which demonstrated an improved pharmacokinetic profile and inhibition of IL-2 production in a mouse.