Synthesis and anti-diabetic activity of novel biphenylsulfonamides as glucagon receptor antagonists

Type 2 diabetes is characterized by chronic hyperglycemia. Insulin, a hormone secreted from pancreatic β-cells, decreases blood glucose levels, and glucagon, a hormone secreted from pancreatic α-cells, increases blood glucose levels by counterregulation of insulin through stimulation of hepatic glucose production. In diabetic patients, dysregulation of glucagon secretion contributes to hyperglycemia. Thus, inhibition of the glucagon receptor is one strategy for the treatment of hyperglycemia in type 2 diabetes. In this paper, we report a series of biphenylsulfonamide derivatives that were designed, synthesized, and then evaluated by cAMP and hepatic glucose production assays as glucagon receptor antagonists. Of these, compound 7aB-3 decreased glucagon-induced cAMP production and glucagon-induced glucose production in the in vitro assays. Glucagon challenge tests and glucose tolerance tests showed that compound 7aB-3 significantly inhibited glucagon-induced glucose increases and improved glucose tolerance. These results suggest that compound 7aB-3 has therapeutic potential for the treatment of type 2 diabetes.

Discovery of thiophene-containing biaryl amide derivatives as novel glucagon receptor antagonists

A novel series of thiophene-containing biaryl amide glucagon receptor (GCGR) antagonists were designed and synthesized. Two compounds of this series, 14f and 14h, exhibited good GCGR binding (IC₅₀  = 6.1 and 4.4 μm, respectively) and cAMP functional activities (IC₅₀  = 4.4 and 14.4 μm, respectively). The possible binding modes of compounds 14f and 14h with GCGR were explored by molecular simulation.

Treatment with the glucagon receptor antagonist LY2409021 increases ambulatory blood pressure in patients with type 2 diabetes

AIMS

To assess the effect of LY2409021 on systolic blood pressure (SBP) in patients with type 2 diabetes.

MATERIALS AND METHODS

This 6-week, randomized, crossover study evaluated the effects of once-daily administration of LY2409021 20 mg vs those of placebo on SBP, diastolic BP (DBP), and mean arterial pressure (MAP) using 24-hour ambulatory BP monitoring (ABPM) in 270 subjects treated with diet/exercise ± metformin. Other measures included changes in glycemic control, serum lipids, and hepatic safety markers.

RESULTS

At 6 weeks of LY2409021 treatment, 24-hour mean SBP was increased, with a least squares mean (LSM) difference of 2.26 mm Hg vs placebo (95% CI: 1.11, 3.40; P  < .001). The 24-hour mean DBP and MAP also increased, with LSM differences of 1.37 mm Hg (95% CI: 0.66, 2.08; P  < .001) and 1.67 mm Hg (95% CI: 0.86, 2.47; P  < .001) vs placebo, respectively. At week 6, LY2409021 treatment reduced glycated hemoglobin (HbA1c) levels, with an LSM difference of -0.49% (-5.4 mmol/mol) (95% CI: -0.56%, -0.42% [-6.1, -4.6 mmol/mol]; P  < .001) vs placebo. Mean HbA1c at baseline was 7.3% (56 mmol/mol). Small but significant changes in serum lipid and aminotransferase levels were observed with LY2409021 treatment (all P  < .05 vs placebo).

CONCLUSIONS

Statistically significant increases in BP, MAP and serum lipid levels were observed with LY2409021 treatment at a dose that lowered HbA1c and glucose levels. These effects may limit the clinical utility of LY2409021 as a chronic treatment for type 2 diabetes.

Synthesis of C-14 radiolabeled glucagon receptor antagonist and its use in a human mass balance study

The synthesis of the radiolabeled glucagon receptor antagonist 1-[¹⁴ C] was accomplished based on decarboxylative iodination of acid 2 followed by "reattachment" of ¹⁴ C carboxylic function. The method allowed a significant reduction in the number of steps in preparation of the radiolabeled compound. Iodide 4, obtained by the halodecarboxylation, was converted to cyanide 5-[¹⁴ C], which was hydrolyzed to provide the radiolabeled acid 2-[¹⁴ C]. Coupling with β-alanine fragment and hydrolysis of ester 6-[¹⁴ C] completed the synthesis of the target molecule 1-[¹⁴ C]. The resulting compound was utilized in a mass balance and metabolism study where hepatic oxidation followed by a trace amount of sulfate conjugation and elimination was the main clearance pathway for 1 in humans.

Glucagon receptor antagonist and GIP agonist combination for diet-induced obese mice

Ablation of glucagon receptor signaling represents a potential treatment option for type 2 diabetes (T2DM). Additionally, activation of glucose-dependent insulinotropic polypeptide (GIP) receptor signaling also holds therapeutic promise for T2DM. Therefore, this study examined both independent and combined metabolic actions of desHis(1)Pro(4)Glu(9)(Lys(12)PAL)-glucagon (glucagon receptor antagonist) and d-Ala(2)GIP (GIP receptor agonist) in diet-induced obese mice. Glucagon receptor binding has been linked to alpha-helical structure and desHis(1)Pro(4)Glu(9)(Lys(12)PAL)-glucagon displayed enhanced alpha-helical content compared with native glucagon. In clonal pancreatic BRIN-BD11 beta-cells, desHis(1)Pro(4)Glu(9)(Lys(12)PAL)-glucagon was devoid of any insulinotropic or cAMP-generating actions, and did not impede d-Ala(2)GIP-mediated (P<0.01 to P<0.001) effects on insulin and cAMP production. Twice-daily injection of desHis(1)Pro(4)Glu(9)(Lys(12)PAL)-glucagon or d-Ala(2)GIP alone, and in combination, in high-fat-fed mice failed to affect body weight or energy intake. Circulating blood glucose levels were significantly (P<0.05 to P<0.01) decreased by all treatments regimens, with plasma and pancreatic insulin elevated (P<0.05 to P<0.001) in all mice receiving d-Ala(2)GIP. Interestingly, plasma glucagon concentrations were decreased (P<0.05) by sustained glucagon inhibition (day 28), but increased (P<0.05) by d-Ala(2)GIP therapy, with a combined treatment resulting in glucagon concentration similar to saline controls. All treatments improved (P<0.01) intraperitoneal and oral glucose tolerance, and peripheral insulin sensitivity. d-Ala(2)GIP-treated mice showed increased glucose-induced insulin secretion in response to intraperitoneal and oral glucose. Metabolic rate and ambulatory locomotor activity were increased (P<0.05 to P<0.001) in all desHis(1)Pro(4)Glu(9)(Lys(12)PAL)-glucagon-treated mice. These studies highlight the potential of glucagon receptor inhibition alone, and in combination with GIP receptor activation, for T2DM treatment.

Glucagon receptor antagonism induces increased cholesterol absorption

Glucagon and insulin have opposing action in governing glucose homeostasis. In type 2 diabetes mellitus (T2DM), plasma glucagon is characteristically elevated, contributing to increased gluconeogenesis and hyperglycemia. Therefore, glucagon receptor (GCGR) antagonism has been proposed as a pharmacologic approach to treat T2DM. In support of this concept, a potent small-molecule GCGR antagonist (GRA), MK-0893, demonstrated dose-dependent efficacy to reduce hyperglycemia, with an HbA1c reduction of 1.5% at the 80 mg dose for 12 weeks in T2DM. However, GRA treatment was associated with dose-dependent elevation of plasma LDL-cholesterol (LDL-c). The current studies investigated the cause for increased LDL-c. We report findings that link MK-0893 with increased glucagon-like peptide 2 and cholesterol absorption. There was not, however, a GRA-related modulation of cholesterol synthesis. These findings were replicated using structurally diverse GRAs. To examine potential pharmacologic mitigation, coadministration of ezetimibe (a potent inhibitor of cholesterol absorption) in mice abrogated the GRA-associated increase of LDL-c. Although the molecular mechanism is unknown, our results provide a novel finding by which glucagon and, hence, GCGR antagonism govern cholesterol metabolism.

Two novel glucagon receptor antagonists prove effective therapeutic agents in high-fat-fed and obese diabetic mice

AIMS

To examine the effect of two novel, enzymatically stable, glucagon receptor peptide antagonists, on metabolic control in two mouse models of obesity/diabetes.

METHOD

The effects of twice daily i.p. administration of desHis(1)Pro(4)Glu(9)-glucagon or desHis(1)Pro(4)Glu(9)Lys(12)FA-glucagon for 10 days on metabolic control in high-fat-fed (HFF; 45% fat) and obese diabetic (ob/ob) mice were compared with saline-treated controls.

RESULTS

Neither analogue altered body weight or food intake in either model over 10 days; however, treatment with each peptide restored non-fasting blood glucose towards normal control values in HFF mice. Basal glucose was also reduced (p < 0.01) in desHis(1)Pro(4)Glu(9)Lys(12)FA-glucagon treated ob/ob mice by day 10, coinciding with increases (p < 0.001) in circulating insulin. At the end of the treatment period, both analogues significantly (p < 0.05-0.01) improved oral and i.p. glucose tolerance (p < 0.05) and peripheral insulin sensitivity, increased pancreatic insulin and glucagon content (p < 0.05-0.01) and decreased (p < 0.05) cholesterol levels in HFF mice. Similarly beneficial metabolic effects on oral glucose tolerance (p < 0.01) and pancreatic insulin content (p < 0.05) were observed in ob/ob mice, especially after desHis(1)Pro(4)Glu(9)Lys(12)FA-glucagon treatment. No significant differences in circulating triglycerides or aspects of indirect calorimetry were noted between peptide treatment groups and respective control HFF and ob/ob mice. Finally, glucagon-mediated elevations of glucose and insulin were significantly (p < 0.05-0.01) annulled after 10 days of desHis(1)Pro(4)Glu(9)-glucagon or desHis(1)Pro(4)Glu(9)Lys(12)FA-glucagon treatment in both animal models.

CONCLUSION

These data indicate that peptide-based glucagon receptor antagonists can reverse aspects of genetically and dietary-induced obesity-related diabetes.