Search

Objective: Pharmacological strategies that engage multiple mechanisms-of-action have demonstrated synergistic benefits for metabolic disease in preclinical models. One approach, concurrent activation of the glucagon-like peptide-1 (GLP-1), glucose-dependent insulinotropic peptide (GIP), and glucagon (Gcg) receptors (i.e. triagonism), combines the anorectic and insulinotropic activities of GLP-1 and GIP with the energy expenditure effect of glucagon. While the efficacy of triagonism in preclinical models is known, the relative contribution of GcgR activation remains unassessed. This work aims to addresses that central question., Methods: Herein, we detail the design of unimolecular peptide triagonists with an empirically optimized receptor potency ratio. These optimized peptide triagonists employ a protraction strategy permitting once-weekly human dosing. Additionally, we assess the effects of these peptides on weight-reduction, food intake, glucose control, and energy expenditure in an established DIO mouse model compared to clinically relevant GLP-1R agonists (e.g. semaglutide) and dual GLP-1R/GIPR agonists (e.g. tirzepatide)., Results: Optimized triagonists normalize body weight in DIO mice and enhance energy expenditure in a manner superior to that of GLP-1R mono-agonists and GLP-1R/GIPR co-agonists., Conclusions: These pre-clinical data suggest unimolecular poly-pharmacology as an effective means to target multiple mechanisms contributing to obesity and further implicate GcgR activation as the differentiating factor between incretin receptor mono- or dual-agonists and triagonists., (Copyright © 2022 The Author(s). Published by Elsevier GmbH.. All rights reserved.)

Antagonism of glucagon's biological action is a proven strategy for decreasing glucose in diabetic animals and patients. To achieve full, potent, and selective suppression, we chemically optimized N-terminally truncated glucagon fragments for the identification and establishment of the minimum sequence peptide, [Glu9]glucagon(6-29) amide ( 11 ) as a full antagonist in cellular signaling and receptor binding (IC 50 = 36 nM). Substitution of Phe6 with l-3-phenyllactic acid (Pla) produced [Pla6, Glu9]glucagon(6-29) amide ( 21 ), resulting in a 3-fold improvement in receptor binding (IC 50 = 12 nM) and enhanced antagonist potency. Further substitution of Glu9 and Asn28 with aspartic acid yielded [Pla6, Asp28]glucagon amide ( 26 ), which demonstrated a further increase in inhibitory potency (IC 50 = 9 nM), and improved aqueous solubility. Peptide 26 and a palmitoylated analogue, [Pla6, Lys10(γGluγGlu-C16), Asp28]glucagon(6-29) amide ( 31 ), displayed sustained duration in vivo action that successfully reversed glucagon-induced glucose elevation in mice.

The continued global growth in the prevalence of obesity coupled with the limited number of efficacious and safe treatment options elevates the importance of innovative pharmaceutical approaches. Combinatorial strategies that harness the metabolic benefits of multiple hormonal mechanisms have emerged at the preclinical and more recently clinical stages of drug development. A priority has been anti-obesity unimolecular peptides that function as balanced, high potency poly-agonists at two or all the cellular receptors for the endocrine hormones glucagon-like peptide-1 (GLP-1), glucose-dependent insulinotropic polypeptide (GIP), and glucagon. This report reviews recent progress in this area, with emphasis on what the initial clinical results demonstrate and what remains to be addressed., Competing Interests: Declaration of Competing Interests PJK, SAM, BF, and RDD are employees of Novo Nordisk. RDD is a holder of intellectual property with Indiana University relating to some of the technology discussed in this review. DPT maintains a research collaboration with Novo Nordisk., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Peptide-based therapeutics commonly suffer from biophysical properties that compromise pharmacology and medicinal use. Structural optimization of the primary sequence is the usual route to address such challenges while trying to maintain as much native character and avoiding introduction of any foreign element that might evoke an immunological response. Glucagon serves a seminal physiological role in buffering against hypoglycemia, but its low aqueous solubility, chemical instability, and propensity to self-aggregate severely complicate its medicinal use. Selective amide bond replacement with metastable ester bonds is a preferred approach to the preparation of peptides with biophysical properties that otherwise inhibit synthesis. We have recruited such chemistry in the design and development of unique glucagon prodrugs that have physical properties suitable for medicinal use and yet rapidly convert to native hormone upon exposure to slightly alkaline pH. These prodrugs demonstrate in vitro and in vivo pharmacology when formulated in physiological buffers that are nearly identical to native hormone when solubilized in conventional dilute hydrochloric acid. This approach provides the best of both worlds, where the pro-drug delivers chemical properties supportive of aqueous formulation and the native biological properties.

Glucagon and thyroid hormone (T 3 ) exhibit therapeutic potential for metabolic disease but also exhibit undesired effects. We achieved synergistic effects of these two hormones and mitigation of their adverse effects by engineering chemical conjugates enabling delivery of both activities within one precisely targeted molecule. Coordinated glucagon and T 3 actions synergize to correct hyperlipidemia, steatohepatitis, atherosclerosis, glucose intolerance, and obesity in metabolically compromised mice. We demonstrate that each hormonal constituent mutually enriches cellular processes in hepatocytes and adipocytes via enhanced hepatic cholesterol metabolism and white fat browning. Synchronized signaling driven by glucagon and T 3 reciprocally minimizes the inherent harmful effects of each hormone. Liver-directed T 3 action offsets the diabetogenic liability of glucagon, and glucagon-mediated delivery spares the cardiovascular system from adverse T 3 action. Our findings support the therapeutic utility of integrating these hormones into a single molecular entity that offers unique potential for treatment of obesity, type 2 diabetes, and cardiovascular disease., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Glucagon (Gcg) 1 serves a seminal physiological role in buffering against hypoglycemia, but its poor biophysical properties severely complicate its medicinal use. We report a series of novel glucagon analogues of enhanced aqueous solubility and stability at neutral pH, anchored by Gcg[Aib16]. Incorporation of 3- and 4-pyridyl-alanine (3-Pal and 4-Pal) enhanced aqueous solubility of glucagon while maintaining biological properties. Relative to native hormone, analogue 9 (Gcg[3-Pal6,10,13, Aib16]) demonstrated superior biophysical character, better suitability for medicinal purposes, and comparable pharmacology against insulin-induced hypoglycemia in rats and pigs. Our data indicate that Pal is a versatile surrogate to natural aromatic amino acids and can be employed as an alternative or supplement with isoelectric adjustment to refine the biophysical character of peptide drug candidates.

Glucagon, an essential regulator of glucose homeostasis, also modulates lipid metabolism and promotes weight loss, as reflected by the wasting observed in glucagonoma patients. Recently, coagonist peptides that include glucagon agonism have emerged as promising therapeutic candidates for the treatment of obesity and diabetes. We developed a novel stable and soluble glucagon receptor (GcgR) agonist, which allowed for in vivo dissection of glucagon action. As expected, chronic GcgR agonism in mice resulted in hyperglycemia and lower body fat and plasma cholesterol. Notably, GcgR activation also raised hepatic expression and circulating levels of fibroblast growth factor 21 (FGF21). This effect was retained in isolated primary hepatocytes from wild-type (WT) mice, but not GcgR knockout mice. We confirmed this link in healthy human volunteers, where injection of natural glucagon increased plasma FGF21 within hours. Functional relevance was evidenced in mice with genetic deletion of FGF21, where GcgR activation failed to induce the body weight loss and lipid metabolism changes observed in WT mice. Taken together, these data reveal for the first time that glucagon controls glucose, energy, and lipid metabolism at least in part via FGF21-dependent pathways.

Glucagon has long been known as a counter-regulatory hormone to insulin of fundamental importance to glucose homeostasis. Its prominent ability to stimulate glycogenolysis and gluconeogenesis, has historically cast this peptide as one hormone where the metabolic consequences of increasing blood glucose levels, especially in obesity, are viewed largely as being deleterious. This perspective may be changing in light of emerging data and reconsideration of historic studies, which suggest that glucagon has beneficial effects on body fat mass, food intake, and energy expenditure. In this review, we discuss the mechanisms of glucagon-mediated body weight regulation as well as possible novel therapeutic approaches in the treatment of obesity and glucose intolerance that may arise from these findings. The paper represents an invited review by a symposium, award winner or keynote speaker at the Society for the Study of Ingestive Behavior [SSIB] Annual Meeting in Portland, July 2009., (Published by Elsevier Inc.)