How May GIP Enhance the Therapeutic Efficacy of GLP-1? Samms, Ricardo J.; Coghlan, Matthew P.; Sloop, Kyle W.
Trends in endocrinology and metabolism,
June 2020, 2020-Jun, 2020-06-00, 20200601, Letnik:
31, Številka:
6
Journal Article
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Glucagon-like peptide-1 (GLP-1) receptor agonists improve glucose homeostasis, reduce bodyweight, and over time benefit cardiovascular health in type 2 diabetes mellitus (T2DM). However, dose-related ...gastrointestinal effects limit efficacy, and therefore agents possessing GLP-1 pharmacology that can also target alternative pathways may expand the therapeutic index. One approach is to engineer GLP-1 activity into the sequence of glucose-dependent insulinotropic polypeptide (GIP). Although the therapeutic implications of the lipogenic actions of GIP are debated, its ability to improve lipid and glucose metabolism is especially evident when paired with the anorexigenic mechanism of GLP-1. We review the complexity of GIP in regulating adipose tissue function and energy balance in the context of recent findings in T2DM showing that dual GIP/GLP-1 receptor agonist therapy produces profound weight loss, glycemic control, and lipid lowering.
Novel ligands possessing agonist activity at both GIP and GLP-1 receptors are being investigated for the treatment of T2DM.The GIP component of dual GIP/GLP-1 receptor agonism is hypothesized to act centrally to enhance GLP-1-induced weight loss.The ability of GIP to target white adipose tissue (WAT) and improve its lipid buffering capacity is proposed to protect from ‘spillover’ of dietary lipids.Pairing the anorexigenic effects of GIP/GLP-1 receptor agonism with the peripheral actions of GIP to promote lipid storage in WAT may be advantageous over the mechanisms of current treatments for T2DM.
Glucagon-like peptide-1 receptor (GLP-1R) agonists are efficacious antidiabetic medications that work by enhancing glucose-dependent insulin secretion and improving energy balance. Currently approved ...GLP-1R agonists are peptide based, and it has proven difficult to obtain small-molecule activators possessing optimal pharmaceutical properties. We report the discovery and mechanism of action of LY3502970 (OWL833), a nonpeptide GLP-1R agonist. LY3502970 is a partial agonist, biased toward G protein activation over β-arrestin recruitment at the GLP-1R. The molecule is highly potent and selective against other class B G protein–coupled receptors (GPCRs) with a pharmacokinetic profile favorable for oral administration. A high-resolution structure of LY3502970 in complex with active-state GLP-1R revealed a unique binding pocket in the upper helical bundle where the compound is bound by the extracellular domain (ECD), extracellular loop 2, and transmembrane helices 1, 2, 3, and 7. This mechanism creates a distinct receptor conformation that may explain the partial agonism and biased signaling of the compound. Further, interaction between LY3502970 and the primate-specific Trp33 of the ECD informs species selective activity for the molecule. In efficacy studies, oral administration of LY3502970 resulted in glucose lowering in humanized GLP-1R transgenic mice and insulinotropic and hypophagic effects in nonhuman primates, demonstrating an effect size in both models comparable to injectable exenatide. Together, this work determined the molecular basis for the activity of an oral agent being developed for the treatment of type 2 diabetes mellitus, offering insights into the activation of class B GPCRs by nonpeptide ligands.
Tirzepatide (LY3298176) is a dual GIP and GLP-1 receptor agonist under development for the treatment of type 2 diabetes mellitus (T2DM), obesity, and nonalcoholic steatohepatitis. Early phase trials ...in T2DM indicate that tirzepatide improves clinical outcomes beyond those achieved by a selective GLP-1 receptor agonist. Therefore, we hypothesized that the integrated potency and signaling properties of tirzepatide provide a unique pharmacological profile tailored for improving broad metabolic control. Here, we establish methodology for calculating occupancy of each receptor for clinically efficacious doses of the drug. This analysis reveals a greater degree of engagement of tirzepatide for the GIP receptor than the GLP-1 receptor, corroborating an imbalanced mechanism of action. Pharmacologically, signaling studies demonstrate that tirzepatide mimics the actions of native GIP at the GIP receptor but shows bias at the GLP-1 receptor to favor cAMP generation over β-arrestin recruitment, coincident with a weaker ability to drive GLP-1 receptor internalization compared with GLP-1. Experiments in primary islets reveal β-arrestin1 limits the insulin response to GLP-1, but not GIP or tirzepatide, suggesting that the biased agonism of tirzepatide enhances insulin secretion. Imbalance toward GIP receptor, combined with distinct signaling properties at the GLP-1 receptor, together may account for the promising efficacy of this investigational agent.
Tirzepatide (LY3298176), a dual GIP and GLP-1 receptor agonist, delivered superior glycemic control and weight loss compared to GLP-1 receptor (GLP-1R) agonism in patients with type 2 diabetes. ...However, the mechanism by which tirzepatide improves efficacy and how GIP receptor (GIPR) agonism contributes is not fully understood. Here, we show that tirzepatide is an effective insulin sensitizer, improving insulin sensitivity in obese mice to a greater extent than GLP-1R agonism. To determine if GIPR agonism contributes, we compared the effect of tirzepatide in obese wild-type and Glp-1r null mice. In the absence of GLP-1R-induced weight loss, tirzepatide improved insulin sensitivity by enhancing glucose disposal in white adipose tissue (WAT). In support, a long-acting GIPR agonist (LAGIPRA) was found to enhance insulin sensitivity by augmenting glucose disposal in WAT. Interestingly, the effect of tirzepatide and LAGIPRA on insulin sensitivity was associated with reduced branched-chain amino (BCAAs) and keto-acids in the circulation. Insulin sensitization was associated with upregulation of genes associated with the catabolism of glucose, lipid and BCAAs in brown adipose tissue. Together, our studies show that tirzepatide improved insulin sensitivity in a weight-dependent and -independent manner. These results highlight how GIPR agonism contributes to the therapeutic profile of dual receptor agonism, offering mechanistic insights into the clinical efficacy of tirzepatide.
SignificanceTirzepatide is a dual agonist of the glucose-dependent insulinotropic polypeptide receptor (GIPR) and the glucagon-like peptide-1 receptor (GLP-1R), which are incretin receptors that ...regulate carbohydrate metabolism. This investigational agent has proven superior to selective GLP-1R agonists in clinical trials in subjects with type 2 diabetes mellitus. Intriguingly, although tirzepatide closely resembles native GIP in how it activates the GIPR, it differs markedly from GLP-1 in its activation of the GLP-1R, resulting in less agonist-induced receptor desensitization. We report how cryogenic electron microscopy and molecular dynamics simulations inform the structural basis for the unique pharmacology of tirzepatide. These studies reveal the extent to which fatty acid modification, combined with amino acid sequence, determines the mode of action of a multireceptor agonist.
Combination approaches for the treatment of metabolic diseases such as obesity and diabetes are becoming increasingly relevant. Co-administration of a glucagon-like peptide-1 receptor (GLP-1R) ...agonist with a cholecystokinin receptor-1 (CCKR1) agonist exert synergistic effects on weight loss in obese rodents. Here, we report on the effects of a novel fusion peptide (C2816) comprised of a stabilized GLP-1R agonist, AC3174, and a CCKR1-selective agonist, AC170222. C2816 was constructed such that AC3174 was linked to the N-terminus of AC170222, thus preserving the C-terminal amide of the CCK moiety. In functional in vitro assays C2816 retained full agonism at GLP-1R and CCKR1 at lower potency compared to parent molecules, whereas a previously reported fusion peptide in the opposite orientation, (pGlu-Gln)-CCK-8/exendin-4, exhibited no activity at either receptor. Acutely, in vivo, C2816 increased cFos in key central nuclei relevant to feeding behavior, and reduced food intake in wildtype (WT), but less so in GLP-1R-deficient (GLP-1RKO), mice. In sub-chronic studies in diet-induced obese (DIO) mice, C2816 exerted superior reduction in body weight compared to co-administration of AC3174 and AC170222 albeit at a higher molar dose. These data suggest that the synergistic pharmacological effects of GLP-1 and CCK pathways can be harnessed in a single therapeutic peptide.
There is considerable interest in GIPR agonism to enhance the insulinotropic and extrapancreatic effects of GIP, thereby improving glycemic and weight control in type 2 diabetes (T2D) and obesity. ...Recent genetic epidemiological evidence has implicated higher GIPR-mediated GIP levels in raising coronary artery disease (CAD) risk, a potential safety concern for GIPR agonism. We therefore aimed to quantitatively assess whether the association between higher GIPR-mediated fasting GIP levels and CAD risk is mediated via GIPR or is instead the result of linkage disequilibrium (LD) confounding between variants at the
locus. Using Bayesian multitrait colocalization, we identified a
missense variant, rs1800437 (G allele; E354), as the putatively causal variant shared among fasting GIP levels, glycemic traits, and adiposity-related traits (posterior probability for colocalization PP
> 0.97; PP explained by the candidate variant PP
= 1) that was independent from a cluster of CAD and lipid traits driven by a known missense variant in
(rs7412; distance to E354 ∼770 Kb;
with E354 = 0.004; PP
> 0.99; PP
= 1). Further, conditioning the association between E354 and CAD on the residual LD with rs7412, we observed slight attenuation in association, but it remained significant (odds ratio OR per copy of E354 after adjustment 1.03; 95% CI 1.02, 1.04;
= 0.003). Instead, E354's association with CAD was completely attenuated when conditioning on an additional established CAD signal, rs1964272 (
with E354 = 0.27), an intronic variant in
(OR for E354 after adjustment for rs1964272: 1.01; 95% CI 0.99, 1.03;
= 0.06). We demonstrate that associations with GIP and anthropometric and glycemic traits are driven by genetic signals distinct from those driving CAD and lipid traits in the
region and that higher E354-mediated fasting GIP levels are not associated with CAD risk. These findings provide evidence that the inclusion of GIPR agonism in dual GIPR/GLP1R agonists could potentiate the protective effect of GLP-1 agonists on diabetes without undue CAD risk, an aspect that has yet to be assessed in clinical trials.
GIP receptor (GIPR) agonism enhances the reduction of food intake and weight loss induced by GLP-1 receptor (GLP-1R) agonism. Recently, GLP-1R agonists have been described that exhibit biased agonism ...as determined using cells engineered to facilitate measuring the two canonical signaling pathways engaged upon binding the GLP-1R. Such “biased agonists” retain the ability to activate the G alpha S/cyclic AMP (cAMP) pathway to a similar magnitude as native GLP-1 but exhibit markedly weaker ability to induce receptor recruitment of beta-arrestin. The prototype biased GLP-1R agonist Exendin-Phe1 (Ex-Phe1) is reported to exhibit greater weight and glucose control in diet-induced obese (DIO) mice than its unbiased parent Exendin-4 (Ex4). Herein, we investigated whether the enhanced weight loss of Ex-Phe1 erodes the ability of GIPR agonism to further enhance the efficacy of GLP-1R agonism. The peptides were first characterized in vitro to validate the biased nature of Ex-Ph1. In cells expressing either the human or murine GLP-1R, Ex-Phe1 activated cAMP signaling to a similar magnitude as GLP-1 and Ex4 but with approximately 5-fold lower potency than Ex4. The maximum effect of Ex-Phe1 upon human or mouse GLP-1R recruitment of beta-arrestin was 20% compared with full efficacy for Ex4 relative to GLP-1. In this assay Ex-Phe1 was marginally less potent than Ex4. In a 14-day osmotic minipump DIO mice study, Ex4 and Ex-Phe1 each dose dependently reduced food intake and lowered body weight. Ex-Phe1 was 10-fold more potent than Ex4, and at the maximum dose, delivered superior weight loss. Combination treatment with d-Ala-GIP resulted in similar additional body weight loss to that achieved by either Ex-Phe1 or Ex4 alone by enhancing food intake reduction and increasing energy expenditure. D-Ala-GIP alone had no effect on body weight. These findings indicate that GIPR agonism enhances GLP-1R agonism mediated weight loss irrespective of the pathway bias nature of the latter.
Disclosure
M. P. Coghlan: Employee; Self; Eli Lilly and Company. K. Sloop: Employee; Self; Eli Lilly and Company. T. Coskun: Employee; Self; Eli Lilly and Company, Stock/Shareholder; Self; Eli Lilly and Company. L. O’farrell: None. A. D. Showalter: None. D. B. Wainscott: Employee; Self; Eli Lilly and Company, Employee; Spouse/Partner; Eli Lilly and Company, Stock/Shareholder; Self; Eli Lilly and Company, Stock/Shareholder; Spouse/Partner; Eli Lilly and Company. C. Stutsman: None. G. Cardona: Employee; Self; Eli Lilly and Company, Stock/Shareholder; Self; Eli Lilly and Company. O. Cabrera: None. J. Alsina-fernandez: None. F. S. Willard: Employee; Self; Eli Lilly and Company.
Funding
Eli Lilly and Company
Dual-agonist molecules combining glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) activity represent an exciting therapeutic strategy for diabetes treatment. ...Although challenging due to shared downstream signalling pathways, determining the relative activity of dual agonists at each receptor is essential when developing potential novel therapeutics. The challenge is exacerbated in physiologically relevant cell systems expressing both receptors. To this end, either GIP receptors (GIPR) or GLP-1 receptors (GLP-1R) were ablated via RNA-guided clustered regularly interspaced short palindromic repeat (CRISPR)/Cas9 endonucleases in the INS-1 pancreatic β-cell line. Multiple clonal cell lines harbouring gene disruptions for each receptor were isolated and assayed for receptor activity to identify functional knockouts (KOs). cAMP production in response to GIPR or GLP-1R activation was abolished and GIP- or GLP-1-induced potentiation of glucose-stimulated insulin secretion (GSIS) was attenuated in the cognate KO cell lines. The contributions of individual receptors derived from cAMP and GSIS assays were confirmed in vivo using GLP-1R KO mice in combination with a monoclonal antibody antagonist of GIPR. We have successfully applied CRISPR/Cas9-engineered cell lines to determining selectivity and relative potency contributions of dual-agonist molecules targeting receptors with overlapping native expression profiles and downstream signalling pathways. Specifically, we have characterised molecules as biased towards GIPR or GLP-1R, or with relatively balanced potency in a physiologically relevant β-cell system. This demonstrates the broad utility of CRISPR/Cas9 when applied to native expression systems for the development of drugs that target multiple receptors, particularly where the balance of receptor activity is critical.
Tirzepatide (TZP), a novel dual GIP and GLP-1 receptor agonist, has demonstrated clinically meaningful weight loss in type 2 diabetes mellitus (T2DM) patients. Preclinical data indicate that TZP ...lowers body weight due to a reduction in caloric intake; however, associated effects on feeding behavior have not been studied. To investigate how TZP affects homeostatic feeding, we examined its effect on markers of satiation (meal size), satiety (meal frequency) and hunger (time-interval between meals) in obese mice. Chronic treatment with TZP dose-dependently lowered body weight and food intake in high-fat fed mice. This reduction in total daily caloric intake was underlined by a reduction in meal size and frequency throughout a 14-day treatment period. Indicating that TZP’s effect on total energy intake is associated with reduced hunger and increased satiety. One driver of the current obesity epidemic is the consumption of highly palatable/calorically dense foods. To determine whether the anorexigenic action of TZP is associated with reward-related feeding, we exposed lean and obese mice to two-choice diet paradigms ((low-fat (6% of kcal from fat) vs. high-fat (40% or 60% of kcal from fat) diets). Importantly, we found that while TZP decreased total calories consumed, it also altered macronutrient preference by increasing the intake of a low-fat diet and reducing intake of a high-fat diet. Furthermore, when exposed to a series of two-choice bottle tests, TZP reduced the consumption of nutritive (fructose and sucrose) and non-nutritive (sucralose) tastants, suggesting that TZP’s anorexigenic action may be linked to the taste and caloric content of food. Taken together, these data indicate that TZP’s ability to lower daily energy intake is mediated by both a reduction in homeostatic and reward-driven food intake.
Disclosure
R. Cosgrove: None. M.P. Antonellis: Employee; Spouse/Partner; Eli Lilly and Company. B. Droz: None. W.C. Roell: Employee; Self; Eli Lilly and Company. Stock/Shareholder; Self; Eli Lilly and Company. K. Sloop: None. J. Moyers: Employee; Self; Eli Lilly and Company. Stock/Shareholder; Self; Eli Lilly and Company. M.P. Coghlan: Employee; Self; Eli Lilly and Company. Stock/Shareholder; Self; Eli Lilly and Company. P. Emmerson: None. T. Coskun: Employee; Self; Eli Lilly and Company. R.J. Samms: Employee; Self; Eli Lilly and Company.
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