Xenopus-derived glucagon-like peptide-1 and polyethylene-glycosylated glucagon-like peptide-1 receptor agonists: long-acting hypoglycaemic and insulinotropic activities with potential therapeutic utilities

Design of Xenopus GLP-1-Based Long-Acting Dual GLP-1/Y2 Receptor Agonists

GLP-1 receptor (GLP-1R) and neuropeptide Y₂ receptor (Y₂R) dual agonists have shown great potential to treat obesity and type 2 diabetes (T2DM). We developed a multitarget strategy to design monomeric agonists based on Xenopus GLP-1 (xGLP-1) and PYY_3-36 analogues with dual activation activities on GLP-1R and Y₂R. A novel peptide, 6q, was obtained via stepwise structure optimization and in vitro receptor screens. In db/db and diet-induced obesity (DIO) mice, 6q produced greater effects on long-term glycemic control and body weight reduction than GLP-1R and Y₂R monoagonist counterparts. Notably, in high-fat diet-induced nonalcoholic steatohepatitis (NASH) mice, 6q treatment significantly reduced hepatic triglyceride and total cholesterol levels and reversed hepatic steatosis compared with GLP-1R monoagonist (liraglutide) treatment. Collectively, these data support the therapeutic potential of our GLP-1R/Y₂R dual agonist 6q as a novel antidiabetic, antiobesity, and antisteatotic agent.

Discovery of once-weekly, peptide-based selective GLP-1 and cholecystokinin 2 receptors co-agonizts

A group of long-acting, peptide-based, and selective GLP-1R/CCK-2R dual agonizts were identified by rational design. Guided by sequence analysis, structural elements of the CCK-2R agonist moiety were engineered into the GLP-1R agonist Xenopus GLP-1, resulting in hybrid peptides with potent GLP-1R/CCK-2R dual activity. Further modifications with fatty acids resulted in novel metabolically stable peptides, among which 3d and 3 h showed potent GLP-1R and CCK-2R activation potencies and comparable stability to semaglutide. In food intake tests, 3d and 3 h also showed a potent reduction in food intake, superior to that of semaglutide. Moreover, the acute hypoglycemic and insulinotropic activities of 3d and 3 h were better than that of semaglutide and ZP3022. Importantly, the limited pica response following 3d and 3 h administration in SD rats preliminarily indicated that the food intake reduction effects of 3d and 3 h are independent of nausea/vomiting. In a 35-day study in db/db mice, every two days administration of 3d and 3 h increased islet areas and numbers, insulin contents, β-cell area, β-cell proliferation, as well as improved glucose tolerance, and decreased HbA1c, to a greater extent than ZP3022 and semaglutide. In a 21-day study in DIO mice, once-weekly administration of 3d and 3 h significantly induced body weight loss, improved glucose tolerance, and normalized lipid metabolism, to a greater extent than semaglutide. The current study showed the antidiabetic and antiobesity potentials of GLP-1R/CCK-2R dual agonizts that warrant further investigation.

A GLP-1/glucagon/CCK-2 receptors tri-agonist provides new therapy for obesity and diabetes

BACKGROUND AND PURPOSE

Glucagon-like peptide-1 receptor (GLP-1R) and glucagon receptor (GCGR) dual agonists have exerted promising therapeutic effects for the treatment of obesity and diabetes in clinical development. Moreover, GLP-1R and cholecystokinin 2 receptor (CCK-2R) dual agonists have been shown to restore pancreas function and improve glycemic control in many preclinical studies. In the present study, we describe for the first time that the beneficial effects of GLP-1R/GCGR and GLP-1R/CCK-2R dual agonists can be integrated into one peptide, resulting in significant anti-diabetes and anti-obesity effectiveness.

EXPERIMENTAL APPROACH

The in vitro potency of a novel GLP-1R/GCGR/CCK-2R tri-agonist (xGLP/GCG/gastrin) against GLP-1R, GCGR, CCK-1R and CCK-2R was determined on cells expressing the corresponding receptors by cAMP accumulation or ERK1/2 phosphorylation assays. The in vivo anti-diabetes and anti-obesity effects of xGLP/GCG/gastrin were studied in both db/db and diet induced obesity (DIO) mice.

KEY RESULTS

xGLP/GCG/gastrin was a potent and selective GLP-1R, GCGR, and CCK-2R tri-agonist. In DIO mice, the metabolic benefits of xGLP-1/GCG/gastrin such as reduction of body weight and hepatic lipid contents were significantly better than those of ZP3022 (GLP-1R/CCK-2R dual agonist) and liraglutide. In the short term study in db/db mice, xGLP/GCG/gastrin treatment exerted considerable effects on increasing islet numbers, islet areas, and insulin content. In the long-term treatment study in db/db mice, xGLP-1/GCG/gastrin displayed a significantly sustained improvement in glucose tolerance and glucose control compared with those of liraglutide, ZP3022, cotadutide (GLP-1R/GCGR dual agonist), and xGLP/GCG-15.

CONCLUSIONS AND IMPLICATIONS

These results demonstrate the therapeutic promise of xGLP-1/GCG/gastrin for obesity and diabetes.

Recent Advances in Incretin-Based Pharmacotherapies for the Treatment of Obesity and Diabetes

The incretin hormone glucagon-like peptide-1 (GLP-1) has received enormous attention during the past three decades as a therapeutic target for the treatment of obesity and type 2 diabetes. Continuous improvement of the pharmacokinetic profile of GLP-1R agonists, starting from native hormone with a half-life of ~2-3 min to the development of twice daily, daily and even once-weekly drugs highlight the pharmaceutical evolution of GLP-1-based medicines. In contrast to GLP-1, the incretin hormone glucose-dependent insulinotropic polypeptide (GIP) received little attention as a pharmacological target, because of conflicting observations that argue activation or inhibition of the GIP receptor (GIPR) provides beneficial effects on systemic metabolism. Interest in GIPR agonism for the treatment of obesity and diabetes was recently propelled by the clinical success of unimolecular dual-agonists targeting the receptors for GIP and GLP-1, with reported significantly improved body weight and glucose control in patients with obesity and type II diabetes. Here we review the biology and pharmacology of GLP-1 and GIP and discuss recent advances in incretin-based pharmacotherapies.

Stapled, Long-Acting Xenopus GLP-1-Based Dual GLP-1/Glucagon Receptor Agonists with Potent Therapeutic Efficacy for Metabolic Disease

Novel peptidic glucagon receptor (GCGR) and glucagon-like peptide 1 receptor (GLP-1R) dual agonists are reported to have increased efficacy over GLP-1R monoagonists for the treatment of diabetes and obesity. We identified a novel Xenopus GLP-1-based dual GLP-1R/GCGR agonist (xGLP/GCG-13) designed with a proper activity ratio favoring the GLP-1R versus the GCGR. However, the clinical utility of xGLP/GCG-13 is limited by its short in vivo half-life. Starting from xGLP/GCG-13, dual Cys mutation was performed, followed by covalent side-chain stapling and serum albumin binder incorporation, resulting in a stabilized secondary structure, enhanced agonist potency at GLP-1R and GCGR, and improved stability. The lead peptide 2c (stapled xGLP/GCG-13 analogue with a palmitic acid albumin binder) exhibits balanced GLP-1R and GCGR activations and potent, long-lasting effects on in vivo glucose control. 2c was further explored pharmacologically in diet-induced obesity and db/db rodent models. Chronic administration of 2c potently induced body weight loss and hypoglycemic effects, improved glucose tolerance, increased energy expenditure, and normalized lipid metabolism and adiposity in relevant animal models. These results indicated that 2c has potential for development as a novel antidiabetic and/or antiobesity drug. Furthermore, we propose that the incorporation of a proper serum protein-binding motif into a di-Cys staple is an effective method for improving the stabilities and bioactivities of peptides. This approach is likely applicable to other therapeutic peptides, such as glucose-dependent insulin-tropic peptide receptor (GIPR) and GLP-1R dual agonists or GLP-1R/GCGR/GIPR triagonists.

Design of novel Xenopus GLP-1-based dual glucagon-like peptide 1 (GLP-1)/glucagon receptor agonists

Dual activation of the glucagon receptor (GCGR) and glucagon-like peptide 1 receptor (GLP-1R) has the potential to lead to an effective therapy for the treatment of diabetes and obesity. Here, we report the discovery of a series of peptides with dual activity on GLP-1R and GCGR that were discovered by rational design. Structural elements of oxyntomodulin (OXM), glucagon or exendin-4 were engineered into the selective GLP-1R agonist Xenopus GLP-1 (xGLP-1) on the basis of sequence analysis, resulting in hybrid peptides with potent dual activity at GLP-1R and GCGR. Further modifications with fatty acid resulted in a novel metabolically stable peptide (xGLP/GCG-15) with enhanced and balanced GLP-1R and GCGR activations. This lead peptide was further explored pharmacologically in both db/db and diet-induced obesity (DIO) rodent models. Chronic administration of xGLP/GCG-15 significantly induced hypoglycemic effects and body weight loss, improved glucose tolerance, and normalized lipid metabolism, adiposity, and liver steatosis in relevant rodent models. These preclinical studies suggest that xGLP/GCG-15 has potential for development as a novel anti-obesity and/or anti-diabetic candidate. Considering the equal effects of xGLP/GCG-15 and the clinical candidate MEDI0382 on reverse hepatic steatosis, it may also be explored as a new therapy for nonalcoholic steatohepatitis (NASH) in the future.

Stapled and Xenopus Glucagon-Like Peptide 1 (GLP-1)-Based Dual GLP-1/Gastrin Receptor Agonists with Improved Metabolic Benefits in Rodent Models of Obesity and Diabetes

Diabetes is characterized by pancreas dysfunction and is commonly associated with obesity. Hypoglycemic agents capable of improving β-cell function and reducing body weight therefore are gaining increasing interest. Though glucagon-like peptide 1 receptor (GLP-1R)/cholecystokinin 2 receptor (CCK-2R) dual agonist ZP3022 potently increases β-cell mass and improves glycemic control in diabetic db/db mice, the in vivo half-life (t_1/2) is short, and its body weight reducing activity is limited. Here, we report the discovery of a series of novel GLP-1R/CCK-2R dual agonists. Starting from Xenopus GLP-1, dual cysteine mutation was conducted followed by covalent side chain stapling and albumin binder incorporation, resulting in a stabilized secondary structure, increased agonist potency, and improved stability. Further C-terminal conjugation of gastrin-6 generated GLP-1R/CCK-2R dual agonists, among which 6a and 6b showed higher stability and hypoglycemic activity than liraglutide and ZP3022. Desirably, 6a and 6b exhibited prominent metabolic benefits in diet-induced obesity mice without causing nausea responses and exerted considerable effects on β-cell restoration in db/db mice. These preclinical studies suggest the potential role of GLP-1R/CCK-2R dual agonists as effective agents for treating diabetes and related metabolic disorders.

Discovery of lixisenatide analogues as long-acting hypoglycemic agents using novel peptide half-life extension technology based on mycophenolic acid

Noncovalent binding of peptides to human serum albumin protects against renal clearance and enzymatic degradation. Herein, we investigated the effect of mycophenolic acid (MPA) albumin binders for improving the stability of peptides. For proof-of-principle, the short acting glucagon-like peptide-1 (GLP-1) receptor agonist lixisenatide was selected and functionalized with different MPA albumin binders. In vitro, all lixisenatide analogues showed well preserved GLP-1 receptor activation potency. High performance affinity chromatography (HPAC) and ultrafiltration analyses indicated that DiMPA was able to confer high albumin affinity to lixisenatide and revealed that affinity is increased for DiMPA modified lixisenatide analogues containing OEG spacers. In db/db mice, the selected peptide 2c showed comparable efficacies to lixisenatide with respect to glucose-lowering and insulinotropic activities. Furthermore, the duration of action of glucose homeostasis of 2c was comparable to semaglutide in db/db mice. Importantly, DiMPA albumin binder did not bring significant toxicity of lixisenatide, as reflected by the comparable toxicity indexes in 2c and semaglutide groups after 2 weeks dosing in normal Kunming mice. Short-term study (21 days) conducted on db/db mice showed the better therapeutic efficacies of 2c than semaglutide on pancreas islets protection. Importantly, in chronic studies (84 days) on db/db mice, 2c exhibited a sustained improvement in glycaemic control, to a greater extent than that of semaglutide. Thus, we propose DiMPA modification as a novel and general method for development of long-acting GLP-1 receptor agonists for type 2 diabetes treatments, and 2c as a promising antidiabetic candidate.

DiMPA albumin binders were effectively applied to lixisenatide to make 2c as a long-acting antidiabetic agent.

PEGylated leuprolide with improved pharmacokinetic properties

Leuprolide, a gonadotropin-releasing hormone (GnRH) agonist widely used in androgen deprivation therapy for the treatment of advanced prostate cancer, suffers from a short circulating half-life like other peptide therapeutics. As an attempt to improve its pharmacokinetic properties, two PEGylated leuprolides with different molecular weight were synthesized utilizing N-hydroxysuccinimidyl (NHS) conjugation chemistry. The reaction conditions, including reaction temperature, reaction time and feed ratio of the reactants, were optimized to obtain a higher yield. Reverse-phase high performance liquid chromatography (RP-HPLC) characterization indicates a high purity of the resulting conjugates. Matrix-assisted laser desorption mass spectrometry (MALDI-MS) characterization suggests a 1:1 PEGylation. ¹H NMR study reveals that the reaction occurs on the imidazolyl group on the histidine residue and the conjugates are stable in pH7.4 aqueous solutions. The in vitro bioactivity of the conjugates was evaluated using both hormone-sensitive and hormone-insensitive cell lines. It was found that the PEGylated peptides can still counteract the stimulatory action of androgens and the mitogenic action of epidermal growth factor on cell proliferation. The in vivo bioactivity of the conjugates was also tested. Like the unmodified peptide, administration of the conjugates to male rats leads to an initial testosterone surge, followed by a suppression of testosterone secretion. Pharmacokinetics of the drugs after i.v. and s.c. administrations were determined. In both cases, a prolonged circulating half-life, an increased AUC, and a decreased Cl_F were observed for the PEGylated drugs.

Novel GLP-1 Analog Supaglutide Stimulates Insulin Secretion in Mouse and Human Islet Beta-Cells and Improves Glucose Homeostasis in Diabetic Mice

Glucagon-like peptide-1 (GLP-1), an incretin hormone plays an important role in regulating glucose homeostasis. The therapeutic use of native GLP-1 is inadequate due to its short in vivo half-life. We recently developed a novel GLP-1 mimetics supaglutide, and demonstrated that this formulation retained native GLP-1 biological activities and possessed long-lasting GLP-1 actions. In this study, we further examined its abilities in regulating blood glucose in diabetic mice. We found that supaglutide stimulated insulin secretion in both mouse and human islets in a dose-dependent fashion. Oral glucose tolerance test conducted in normal ICR mice showed that supaglutide significantly decreased postprandial glucose excursions in a dose-dependent fashion. In type 2 diabetic db/db mice, a single-dose injection of supaglutide significantly decreased blood glucose levels, and this efficacy was lasted for at least 72 h in a dose-dependent fashion. During a 4-weeks intervention course supaglutide (twice injections per week) dose-dependently and significantly decreased fasting and random blood glucose levels in hyperglycemic db/db mice. Supaglutide, at a dose of 1.2 mg/kg, significantly reduced serum fructosamine levels. This was associated with significant enlargement of beta-cell mass, increased pancreatic insulin content, and increased plasma insulin level. Notably, during the intervention course supaglutide significantly reduced body-weight gain in these obese diabetic mice, associated with reduced fat mass (but not the lean mass), improved lipid profile, i.e., declined serum triglyceride, and free fatty acid levels compared to the placebo control. These finding reveals that supaglutide exerts beneficial effects in regulating blood glucose and lipid homeostasis in diabetic db/db mice.

Novel mono-lipidated dimeric glucagon-like peptide-1 receptor agonist with improved long-acting and hypoglycemic activity

Dimerization is a useful tool to boost ligand–receptor interaction. Both lipidation and dimerization effectively prolong the short half-life (t_1/2) of peptides by facilitating binding with serum albumin and increasing hydrodynamic size. Here, we described two novel GLP-1 conjugates with high glucagon-like peptide-1 (GLP-1) receptor activation potencies, dimerized GLP-1 (Di-GLP-1) and lipidated Di-GLP-1 (Lip-Di-GLP-1). Di-GLP-1 and Lip-Di-GLP-1 were prepared through cysteine–maleimide specific coupling reactions using Gly₈-Cys₃₁-GLP-1, bis-maleimide amine, and activated palmitic acid. The receptor activation potencies of Di-GLP-1 and Lip-Di-GLP-1 were 13.6-fold and 9.5-fold higher than GLP-1, respectively. The in vivo hypoglycemic and insulinotropic activities of Di-GLP-1 and Lip-Di-GLP-1 were also better than GLP-1 in db/db mice. Furthermore, Lip-Di-GLP-1 was found to have greater circulating t_1/2 than synthesized liraglutide by 1.8-fold. Accordingly, the improved pharmacokinetic profiles of Lip-Di-GLP-1 resulted in protracted antidiabetic effects as confirmed by hypoglycemic duration test. Moreover, Lip-Di-GLP-1 administered in mice potently inhibits gastric emptying and reduce food intake. Chronic Lip-Di-GLP-1 treatment in db/db mice resulted in significant improvements in food intake, body weight, pancreatic function and corrected hyperglycemia, which was more effective than synthesized liraglutide. Our research indicated that combined dimerization and lipidation were effectively applied to GLP-1, and the preclinical results suggested the potential usage of Lip-Di-GLP-1 as a long-acting antidiabetic agent.

Dimerization and lipidation were effectively applied to GLP-1 to make Lip-Di-GLP-1 as a long-acting antidiabetic agent.

Xenopus-derived glucagon-like peptide-1 and polyethylene-glycosylated glucagon-like peptide-1 receptor agonists: long-acting hypoglycaemic and insulinotropic activities with potential therapeutic utilities

BACKGROUND AND PURPOSE

Incretin-based therapies based on glucagon-like peptide-1 (GLP-1) receptor agonists are effective treatments of type 2 diabetes. Abundant research has focused on the development of long-acting GLP-1 receptor agonists. However, all GLP-1 receptor agonists in clinical use or development are based on human or Gila GLP-1. We have identified a potent GLP-1 receptor agonist, xGLP-1B, based on Xenopus GLP-1.

EXPERIMENTAL APPROACH

To further modify the structure of xGLP-1B, alanine scanning was performed to study the structure -activity relationship of xGLP-1B. Two strategies were then employed to improve bioactivity. First, the C-terminal tail of lixisenatide was appended to cysteine-altered xGLP-1B analogues. Second, polyethylene glycol (PEG) chains with different molecular weights were conjugated with the peptides, giving a series of PEGylated conjugates. Comprehensive bioactivity studies of these conjugates were performed in vitro and in vivo.

RESULTS

From the in vitro receptor activation potency and in vivo acute hypoglycaemic activities of conjugates 25 -36, 33 was identified as the best candidate for further biological assessments. Conjugate 33 exhibited prominent hypoglycaemic and insulinotropic activities, as well as improved pharmacokinetic profiles in vivo. The prolonged antidiabetic duration of 33 was further confirmed by pre-oral glucose tolerance tests (OGTT) and multiple OGTT. Furthermore, chronic treatment of db/db mice with 33 ameliorated non-fasting blood glucose and insulin levels, reduced HbA1c values and normalized their impaired glucose tolerance. Importantly, no in vivo toxicity was observed in mice treated with 33.

CONCLUSIONS AND IMPLICATIONS

Peptide 33 is a promising long-acting type 2 diabetes therapeutic deserving further investigation.