Discovery and investigation of a novel class of thiophene-derived antagonists of the human glucagon receptor

2-Aminothiophene derivatives as a new class of positive allosteric modulators of glucagon-like peptide 1 receptor

We report the discovery of two new 2-aminothiophene based small molecule positive allosteric modulators (PAMs) of glucagon-like peptide 1 receptor (GLP-1R) for the treatment of type 2 diabetes. One of the chemotypes, (S-1), has a molecular weight of 239 g/mol, the smallest molecule among all reported GLP-1R PAMs. When combined with GLP-1 peptide, S-1 increased the GLP-1R activity in a dose-dependent manner in a cell-based assay. When combined with the peptide agonist of vasoactive intestinal polypeptide receptor 1 (VIPR1), S-1 showed no specific activity on VIPR1, another class B GPCR present in the same HEK293-CREB cell line. Insulin secretion studies found S-1 combined with GLP-1 increased insulin secretion by 1.5-fold at 5 μM. In a mechanistic study, evidence is provided that the synergistic effect of S-1 with GLP-1 may be partly due to the enhanced impact on CREB based phosphorylation. Given the favorable profile of these chemotypes, the work reported herein suggests that 2-aminothiophene derivatives are a new and promising class of GLP-1R PAMs.

Probing Hepatic Glucose Metabolism via 13C NMR Spectroscopy in Perfused Livers-Applications to Drug Development

Despite being first published over 40 years ago, the combination of ¹³C nuclear magnetic resonance spectroscopy (NMR) and the isolated perfused liver preparation remains a unique and relevant approach in investigating the effects of pharmacological interventions on hepatic metabolism. The use of intact, perfused livers maintains many metabolic reactions at their respective rates in vivo, while the use of ¹³C-labelled substrates in combination with ¹³C NMR allows for a detailed study of specific pathways, as well as the design of robust assays which can be used to evaluate novel pharmacological agents. In this review article, we share some of the methods used to probe glucose metabolism, and highlight key findings and successes derived from the application of this specialized technique to the area of drug development for diabetes and related metabolic disorders.

Synthesis, Crystal Structure, Spectroscopic Characterization, DFT Calculations and Cytotoxicity Assays of a New Cu(II) Complex with an Acylhydrazone Ligand Derived from Thiophene

A new Cu(II) complex is synthetized by the reaction of copper nitrate and a N-acylhydrazone ligand obtained from the condensation of o-vanillin and 2-thiophecarbohydrazide (H2L). The solid-state structure of [Cu(HL)(H2O)](NO3)·H2O, or CuHL for simplicity, was determined by X-ray diffraction. In the cationic complex, the copper center is in a nearly squared planar environment with the nitrate interacting as a counterion. CuHL was characterized by spectroscopic techniques, including solid-state FTIR, Raman, electron paramagnetic resonance (EPR) and diffuse reflectance and solution UV-Vis electronic spectroscopy. Calculations based on the density functional theory (DFT) assisted the interpretation and assignment of the spectroscopic data. The complex does not show relevant antioxidant activity evaluated by the radical cation of 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) method, being even less active than the free ligand as a radical quencher. Cytotoxicity assays of CuHL against three human tumor cell lines, namely MG-63, A549 and HT-29, revealed an important enhancement of the effectiveness as compared with both the ligand and the free metal ion. Moreover, its cytotoxic effect was remarkably stronger than that of the reference metallodrug cisplatin in all cancer cell lines tested, a promissory result in the search for new metallodrugs of essential transition metals.

Synthesis of Tetrahydrobenzo[b]thiophene-3-carbohydrazide Derivatives as Potential Anti-cancer Agents and Pim-1 Kinase Inhibitors

BACKGROUND

Tetrahydrobenzo[b]thiophene derivatives are well known to be biologically active compounds and many of them occupy a wide range of anticancer agent drugs.

OBJECTIVE

One of the main aim of this work was to synthesize target molecules not only possessing anti-tumor activities but also kinase inhibitors. To achieve this goal, our strategy was to synthesize a series of 4,5,6,7- tetrahydrobenzo[b]thiophene-3-carbohydrazide derivatives using cyclohexan-1,4-dione and cyanoacetylhydrazine to give the 2-amino-6-oxo-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carbohydrazide (3) as the key starting material for many heterocyclization reactions.

METHODS

Compound 3 was reacted with some aryldiazonium salts and the products were cyclised when reacted with either malononitrile or ethyl cyanoacetate. Thiazole derivatives were also obtained through the reaction of compound 3 with phenylisothiocyanate followed by heterocyclization with α-halocarbonyl derivatives. Pyrazole, triazole and pyran derivatives were also obtained.

RESULTS

The compounds obtained in this work were evaluated for their in-vitro cytotoxic activity against c-Met kinase, and the six typical cancer cell lines (A549, H460, HT-29, MKN-45, U87MG, and SMMC-7721). The results of anti-proliferative evaluations and c-Met kinase, Pim-1 kinse inhibitions revealed that some compounds showed high activities.

CONCLUSION

The most promising compounds 5b, 5c, 7c, 7d, 11b, 14a, 16b, 18b, 19, 21a, 23c, 23d and 23i against c-Met kinase were further investigated against the five tyrosin kinases (c-Kit, Flt-3, VEGFR-2, EGFR, and PDGFR). Compounds 5b, 5c, 7d, 7e, 11b, 11c, 16c, 16d, 18c, 19, 23e, 23k and 23m were selected to examine their Pim-1 kinase inhibitions activity where compounds 7d, 7e, 11b, 11c, 16d, 18c and 23e showed high activities. All of the synthesized compounds have no impaired effect toward the VERO normal cell line.

Effect of hydrophobic and hydrogen bonding interactions on the potency of ß-alanine analogs of G-protein coupled glucagon receptor inhibitors

G-protein coupled glucagon receptors (GCGRs) play an important role in glucose homeostasis and pathophysiology of Type-II Diabetes Mellitus (T2DM). The allosteric pocket located at the trans-membrane domain of GCGR consists of hydrophobic (TM5) and hydrophilic (TM7) units. Hydrophobic interactions with the amino acid residues present at TM5, found to facilitate the favorable orientation of antagonist at GCGR allosteric pocket. A statistically robust and highly predictive 3D-QSAR model was developed using 58 β-alanine based GCGR antagonists with significant variation in structure and potency profile. The correlation coefficient (R² ) and cross-validation coefficient (Q² ) of the developed model were found to be 0.9981 and 0.8253, respectively at the PLS factor of 8. The analysis of the favorable and unfavorable contribution of different structural features on the glucagon receptor antagonists was done by 3D-QSAR contour plots. Hydrophobic and hydrogen bonding interactions are found to be main dominating non-bonding interactions in docking studies. Presence of highest occupied molecular orbital (HOMO) in the polar part and lowest unoccupied molecular orbital (LUMO) in the hydrophobic part of antagonists leads to favorable protein-ligand interactions. Molecular mechanics/generalized born surface area (MM/GBSA) calculations showed that van der Waals and nonpolar solvation energy terms are crucial components for thermodynamically stable binding of the inhibitors. The binding free energy of highly potent compound was found to be -63.475 kcal/mol; whereas the least active compound exhibited binding energy of -41.097 kcal/mol. Further, five 100 ns molecular dynamics simulation (MD) simulations were done to confirm the stability of the inhibitor-receptor complex. Outcomes of the present study can serve as the basis for designing improved GCGR antagonists.

Heterocyclization of 2-Arylidenecyclohexan-1,3-dione: Synthesis of Thiophene, Thiazole, and Isoxazole Derivatives with Potential Antitumor Activities

BACKGROUND

Thiophene, thiazole, and isoxazole derivatives are present in a wide range of natural and synthetic compounds with heterogeneous pharmacological activity. Due to their structural diversity, they are some of the most versatile classes of compounds for anticancer drug design and discovery.

OBJECTIVE

Thiophene, thiazole, and isoxazole derivatives were herein designed with a dual purpose: as antiproliferative agents and kinase inhibitors.

METHODS

The test compounds were synthesized in moderate to high yields through a simple methodology. Tetrahydrobenzo[b]thiophen-5-one derivatives 5a-f were prepared from the reaction of 2-arylidencyclohexan- 1,3-dione 3a-c with elemental sulfur and either of malononitrile (4a) or ethyl cyanoacetate (4b) in 1,4-dioxan in the presence of triethylamine. Compounds 5a,b were used for the synthesis of thiophene, thiazole, and isoxazole derivatives through their reactions with different chemical reagents.

RESULTS

Antiproliferative evaluations, c-Met kinase, and Pim-1 kinase inhibitions were performed where some compounds revealed high activities. In all cases, antiproliferative activity and the kinase inhibitions were performed against six cancer cell lines and five tyrosine kinases, respectively. Where the most cytotoxic compounds were 3c, 5d, and 16c with IC50's 0.29, 0.68, and 0.42μM, respectively, against the A549 cell line.

CONCLUSION

The anti-proliferative activities of the newly synthesized compounds were evaluated against the six cancer cell lines (A549, HT-29, MKN-45, U87MG, SMMC-7721, and H460). The most potent compounds toward the cancer cell lines (3a, 3c, 5d, 7c, 11c, 16a, and 16c) were further investigated towards the five tyrosine kinases (c-kit, FIT-3, VEGFR-2, EGFR, and PDGFR). Compounds 3c, 5d, and 16c were selected for testing of their inhibition for the Pim-1 kinase due to their anti-proliferation activities against the cancer cell lines and their high activities against the tyrosine kinases.

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.

Uses of Cyclohexan-1,4-dione for the Synthesis of 2-Amino-4,5-dihydrobenzo[b]thiophen-6(7H)-one Derivatives with Anti-proliferative and Pim-1 Kinase Activities

The reaction of cyclohexan-1,4-dione with elemental sulfur and any of the 2-cyano-N-arylacetamide derivatives 2a-c gave the 2-amino-4,5-dihydrobenzo[b]thiophen-6(7H)-one derivatives 3a-c to be used in some heterocyclization reactions. The multicomponent reactions of any of compounds 3a-c with aromatic aldehydes 6a-c and either of malononitrile or ethylcyanoacetate gave the 5,9-dihydro-4H-thieno[2,3-f]chromene derivatives 9a-r, respectively. The anti-proliferative evaluation of the newly synthesized compounds against the six cancer cell lines A549, HT-29, MKN-45, U87MG, SMMC-7721 and H460 showed that the nine compounds 3c, 5c, 9e, 9h, 9i, 9j, 9l, 9q, 11e and 13e with highest cytotoxcity. Toxicity of these compounds against shrimp larvae revealed that compounds 3c, 9j, 9q, and 13e showed no toxicity against the tested organisms. The c-Met kinase inhibition of the most potent compounds showed that compounds 9j, 9q, 10e, 12e and 13e have the highest activities. Compounds 9j, 9l, 9q and 11e showed high activity towards tyrosine kinases. Moreover, compounds 9j, 9q and 13e showed the highest inhibitor activity towards Pim-1 kinase.

Landmark studies on the glucagon subfamily of GPCRs: from small molecule modulators to a crystal structure

The glucagon subfamily of class B G protein-coupled receptors (GPCRs) has been proposed to be a crucial drug target for the tretmaent of type 2 diabetes. The challenges associated with determining the crystal structures of class B GPCRs relate to their large amino termini and the lack of available small molecule ligands to stabilize the receptor proteins. Following our discovery of non-peptidic agonists for glucagon-like peptide-1 receptor (GLP-1R) that have therapeutic effects, we initiated collaborative efforts in structural biology and recently solved the three-dimensional (3D) structure of the human glucagon receptor (GCGR) 7-transmembrane domain, providing in-depth information about the underlying signaling mechanisms. In this review, some key milestones in this endeavor are highlighted, including discoveries of small molecule ligands, their roles in receptor crystallization, conformational changes in transmembrane domains (TMDs) upon activation and structure-activity relationship analyses.

Recent Progress in the Use of Glucagon and Glucagon Receptor Antago-nists in the Treatment of Diabetes Mellitus

Glucagon is an important pancreatic hormone, released into blood circulation by alpha cells of the islet of Langerhans. Glucagon induces gluconeogenesis and glycogenolysis in hepatocytes, leading to an increase in hepatic glucose production and subsequently hyperglycemia in susceptible individuals. Hyperglucagonemia is a constant feature in patients with T2DM. A number of bioactive agents that can block glucagon receptor have been identified. These glucagon receptor antagonists can reduce the hyperglycemia associated with exogenous glucagon administration in normal as well as diabetic subjects. Glucagon receptor antagonists include isoserine and beta-alanine derivatives, bicyclic 19-residue peptide BI-32169, Des-His1-[Glu9] glucagon amide and related compounds, 5-hydroxyalkyl-4-phenylpyridines, N-[3-cano-6- (1,1 dimethylpropyl)-4,5,6,7-tetrahydro-1-benzothien-2-yl]-2-ethylbutamide, Skyrin and NNC 250926. The absorption, dosage, catabolism, excretion and medicinal chemistry of these agents are the subject of this review. It emphasizes the role of glucagon in glucose homeostasis and how it could be applied as a novel tool for the management of diabetes mellitus by blocking its receptors with either monoclonal antibodies, peptide and non-peptide antagonists or gene knockout techniques.

Antidiabetic agents: past, present and future

Treatment of diabetes mellitus requires, at a certain stage of its course, drug intervention. This article reviews the properties of available antidiabetic medications and highlights potential targets for developing newer and safer drugs. Antidiabetic agents are grouped in the article as parts I, II and III according to the history of development. Part I groups early developed drugs, during the 20th century, including insulin, sulfonylureas, the metiglinides, insulin sensitizers, biguanides and α-glucosidase inhibitors. Part II groups newer drugs developed during the early part of the 21st century, the past decade, including GLP-1 analogs, DPP-VI inhibitors, amylin analogs and SGLT2 inhibitors. Part III groups potential targets for future design of newer antidiabetic agents with less adverse effects than the currently available antidiabetic drugs.

Anti-diabetic efficacy and impact on amino acid metabolism of GRA1, a novel small-molecule glucagon receptor antagonist

Hyperglucagonemia is implicated in the pathophysiology of hyperglycemia. Antagonism of the glucagon receptor (GCGR) thus represents a potential approach to diabetes treatment. Herein we report the characterization of GRA1, a novel small-molecule GCGR antagonist that blocks glucagon binding to the human GCGR (hGCGR) and antagonizes glucagon-induced intracellular accumulation of cAMP with nanomolar potency. GRA1 inhibited glycogenolysis dose-dependently in primary human hepatocytes and in perfused liver from hGCGR mice, a transgenic line of mouse that expresses the hGCGR instead of the murine GCGR. When administered orally to hGCGR mice and rhesus monkeys, GRA1 blocked hyperglycemic responses to exogenous glucagon. In several murine models of diabetes, acute and chronic dosing with GRA1 significantly reduced blood glucose concentrations and moderately increased plasma glucagon and glucagon-like peptide-1. Combination of GRA1 with a dipeptidyl peptidase-4 inhibitor had an additive antihyperglycemic effect in diabetic mice. Hepatic gene-expression profiling in monkeys treated with GRA1 revealed down-regulation of numerous genes involved in amino acid catabolism, an effect that was paralleled by increased amino acid levels in the circulation. In summary, GRA1 is a potent glucagon receptor antagonist with strong antihyperglycemic efficacy in preclinical models and prominent effects on hepatic gene-expression related to amino acid metabolism.

Discovery of a novel glucagon receptor antagonist N-[(4-{(1S)-1-[3-(3, 5-dichlorophenyl)-5-(6-methoxynaphthalen-2-yl)-1H-pyrazol-1-yl]ethyl}phenyl)carbonyl]-β-alanine (MK-0893) for the treatment of type II diabetes

A potent, selective glucagon receptor antagonist 9m, N-[(4-{(1S)-1-[3-(3,5-dichlorophenyl)-5-(6-methoxynaphthalen-2-yl)-1H-pyrazol-1-yl]ethyl}phenyl)carbonyl]-β-alanine, was discovered by optimization of a previously identified lead. Compound 9m is a reversible and competitive antagonist with high binding affinity (IC(50) of 6.6 nM) and functional cAMP activity (IC(50) of 15.7 nM). It is selective for glucagon receptor relative to other family B GPCRs, showing IC(50) values of 1020 nM for GIPR, 9200 nM for PAC1, and >10000 nM for GLP-1R, VPAC1, and VPAC2. Compound 9m blunted glucagon-induced glucose elevation in hGCGR mice and rhesus monkeys. It also lowered ambient glucose levels in both acute and chronic mouse models: in hGCGR ob/ob mice it reduced glucose (AUC 0-6 h) by 32% and 39% at 3 and 10 mpk single doses, respectively. In hGCGR mice on a high fat diet, compound 9m at 3, and 10 mpk po in feed lowered blood glucose levels by 89% and 94% at day 10, respectively, relative to the difference between the vehicle control and lean hGCGR mice. On the basis of its favorable biological and DMPK properties, compound 9m (MK-0893) was selected for further preclinical and clinical evaluations.

Small molecule drug discovery at the glucagon-like peptide-1 receptor

The therapeutic success of peptide glucagon-like peptide-1 (GLP-1) receptor agonists for the treatment of type 2 diabetes mellitus has inspired discovery efforts aimed at developing orally available small molecule GLP-1 receptor agonists. Although the GLP-1 receptor is a member of the structurally complex class B1 family of GPCRs, in recent years, a diverse array of orthosteric and allosteric nonpeptide ligands has been reported. These compounds include antagonists, agonists, and positive allosteric modulators with intrinsic efficacy. In this paper, a comprehensive review of currently disclosed small molecule GLP-1 receptor ligands is presented. In addition, examples of "ligand bias" and "probe dependency" for the GLP-1 receptor are discussed; these emerging concepts may influence further optimization of known molecules or persuade designs of expanded screening strategies to identify novel chemical starting points for GLP-1 receptor drug discovery.

The Gewald multicomponent reaction

The Gewald reaction of sulfur, cyanoacetic acid derivatives, and oxo-component (G-3CR) yielding highly substituted 2-aminothiophene derivatives has seen diverse applications in combinatorial and medicinal chemistry. Its products are of great use in pharmaceutical industry mainly as small molecular weight inhibitors. We herein review synthetic scope and variations, usage, and structural biology of Gewald products.

Discovery of potent, orally active benzimidazole glucagon receptor antagonists

The discovery and optimization of potent and selective aminobenzimidazole glucagon receptor antagonists are described. One compound possessing moderate pharmacokinetic properties in multiple preclinical species was orally efficacious at inhibiting glucagon-mediated glucose excursion in transgenic mice expressing the human glucagon receptor, and in rhesus monkeys. The compound also significantly lowered glucose levels in a murine model of diabetes.

New beta-alanine derivatives are orally available glucagon receptor antagonists

A weak human glucagon receptor antagonist with an IC50 of 7 microM was initially found by screening of libraries originally targeted to mimic the binding of the glucagon-like peptide (GLP-1) hormone to its receptor. Optimization of this hit for binding affinity for the glucagon receptor led to ligands with affinity in the nanomolar range. In addition to receptor binding, optimization efforts were made to stabilize the molecules against fast metabolic turnover. A potent antagonist of the human human glucagon receptor was obtained that had 17% oral availability in rats with a plasma half-life of 90 min. The major metabolites of this lead were identified and used to further optimize this series with respect to pharmacokinetic properties. This final optimization led to a potent glucagon antagonist that was orally available in rats and dogs and was efficacious in lowering blood glucose levels in a diabetic animal model.

Cloning and expression of canine glucagon receptor and its use to evaluate glucagon receptor antagonists in vitro and in vivo

Glucose homeostasis is maintained by the combined actions of insulin and glucagon. Hyperglucagonemia and/or elevation of glucagon/insulin ratio have been reported in diabetic patients and in animal models of diabetes. Therefore, antagonizing glucagon receptor function has long been considered a useful approach to lower hyperglycemia. Dogs serve as an excellent model for studying glycemic control and various aspects of glucagon biology in vivo; however, the amino acid sequence of the dog glucagon receptor has not been reported. To better understand the pharmacology of the dog glucagon receptor and to characterize glucagon receptor antagonists, we cloned a cDNA corresponding to the glucagon receptor from dog liver RNA. The dog glucagon receptor shares a significant (>75%) homology at both nucleotide and amino acid levels with the glucagon receptor from human, monkey, mouse, and rat. The protein is highly conserved among all species in areas corresponding to the 7 trans-membrane domains. However, it shows significant divergence at the carboxy terminus such that the receptor from dog has the longest cytoplasmic tail among all species examined. When expressed in chinese hamster ovary cells, the dog glucagon receptor bound [125I]Glucagon with a K(d) of 477+/-106 pM. Glucagon stimulated the rise of intracellular cAMP levels in these cells with an EC(50) of 9.6+/-1.7 nM and such effects could be blocked by known peptidyl and non-peptidyl small molecule antagonists. In addition we show that a small molecule glucagon receptor antagonist with significant activity in cell based assays also blocked the ability of glucagon to induce elevation in blood glucose in beagle dogs. These data demonstrate that the cloned cDNA encodes a functional dog glucagon receptor. The availability of the dog cDNA will facilitate the understanding of glucagon pharmacology and aid in the characterization of novel glucagon antagonists that may serve as anti-hyperglycemic treatment for type 2 diabetes mellitus.

Class B GPCRs: a hidden agonist within?

Class B G protein-coupled receptors (GPCRs) regulate a wide range of endocrine and neuroendocrine functions and are endogenously stimulated by moderately large peptide hormones. Current evidence suggests that the carboxyl termini of cognate peptides bind to the amino terminus of their G protein-coupled receptors (GPCRs) and that the peptides' amino terminal segments then dock to the heptahelical receptor portion to induce signaling. In this issue of Molecular Pharmacology, Dong et al. (p. 206) propose an alternative model of ligand-induced class B GPCR activation. Based primarily on studies with the secretin receptor, a prototype class B family member, they provide evidence that the endogenous peptide hormone does not function as an activator per se. Instead, this hormone (secretin) exposes a hidden, built-in agonist epitope that is present within the amino terminus of its target GPCR. Isolated oligopeptide fragments containing this epitope act as full agonists on the secretin receptor despite their lack of amino acid homology with the secretin hormone. These nonconventional agonists can be minimized to tripeptide molecules and still maintain biological activity. The study to be discussed introduces a novel paradigm of class B GPCR function, and may facilitate the elusive goal of finding small molecule agonist drugs for this therapeutically attractive group of receptors.

Direct observation (NMR) of the efficacy of glucagon receptor antagonists in murine liver expressing the human glucagon receptor

The demonstration of pharmacodynamic efficacy of novel chemical entities represents a formidable challenge in the early exploration of synthetic lead classes. Here, we demonstrate a technique to validate the biological efficacy of novel antagonists of the human glucagon receptor (hGCGR) in the surgically removed perfused liver prior to the optimization of the pharmacokinetic properties of the compounds. The technique involves the direct observation by (13)C NMR of the biosynthesis of [(13)C]glycogen from [(13)C]pyruvate via the gluconeogenic pathway. The rapid breakdown of [(13)C]glycogen (glycogenolysis) following the addition of 50 pM exogenous glucagon is then monitored in real time in the perfused liver by (13)C NMR. The concentration-dependent inhibition of glucagon-mediated glycogenolysis is demonstrated for both the peptidyl glucagon receptor antagonist 1 and structurally diverse synthetic antagonists 2-7. Perfused livers were obtained from a transgenic mouse strain that exclusively expresses the functional human glucagon receptor, conferring human relevance to the activity observed with glucagon receptor antagonists. This technique does not provide adequate quantitative precision for the comparative ranking of active compounds, but does afford physiological evidence of efficacy in the early development of a chemical series of antagonists.

Discovery of novel, potent, and orally active spiro-urea human glucagon receptor antagonists

A novel class of spiro-ureas has been discovered as potent human glucagon receptor antagonists in both binding and functional assays. Preliminary studies have revealed that compound 15 is an orally active human glucagon receptor antagonist in a transgenic murine pharmacodynamic model at 10 and 30 mpk. Compound 15 is orally bioavailable in several preclinical species and shows selectivity toward cardiac ion channels and other family B receptors, such as hGIP1 and hGLP.