Incretins (GLP-1 receptor agonists and dual/triple agonists) and the liver

Investigational and emerging gastric inhibitory polypeptide (GIP) receptor-based therapies for the treatment of obesity

INTRODUCTION

One billion people live with obesity. The most promising medications for its treatment are incretin-based therapies, based on enteroendocrine peptides released in response to oral nutrients, specifically glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic peptide (GIP). The mechanisms by which GLP-1 receptor agonism cause weight reduction are becoming increasingly understood. However, the mechanisms by which GIP receptor-modulating medications cause weight loss remain to be clarified.

AREAS COVERED

This review describes GLP-1 and GIP physiology and explores the conflicting data regarding GIP and weight management. It details examples of how to reconcile the contradictory findings that both GIP receptor agonism and antagonism cause weight reduction. Specifically, it discusses the concept of 'biased agonism' wherein exogenous peptides cause different post-receptor signaling patterns than native ligands. It discusses how GIP effects in adipose tissue and the central nervous system may cause weight reduction. It describes GIP receptor-modulating compounds and their most current trials regarding weight reduction.

EXPERT OPINION

Effects of GIP receptor-modulating compounds on different tissues have implications for both weight reduction and other cardiometabolic diseases. Further study is needed to understand the implications of GIP agonism on not just weight reduction, but also cardiovascular disease, liver disease, bone health and fat storage.

Pharmacotherapy of Weight-loss and Obesity with a Focus on GLP 1-Receptor Agonists

Obesity is a disease of epidemic proportions in the United States and contributes to morbidity and mortality for a large part of the population. In addition, the financial costs of this disease to society are high. Lifestyle modifications are key to prevention and treatment but adherence and long-term success have been challenging. Bariatric surgery has been available and pharmacologic approaches, first developed in the 1950s, continue to be an option; however, existing formulations have not provided optimal clinical efficacy and have had many concerning adverse effects. Over the last decade, glucagon-like peptide-1 (GLP-1) receptor agonists, a novel group of medications for the treatment of type 2 diabetes, were found to produce significant weight loss. Several formulations, at higher doses, received FDA approval for the treatment of obesity or those overweight with weight-related co-morbidities. More hormone-based therapies were and are being developed, some with dual or triple-receptor agonist activity. Their use, however, is not without questions and concerns as to long-term safety and efficacy, problems with cost and reimbursement, and how their use may intersect with public health efforts to manage the obesity epidemic. This review will focus on the GLP-1 receptor agonists currently used for weight loss and discuss their pharmacology, pertinent research findings establishing their benefits and risks, issues with prescribing these medications, and a perspective from a public health point of view.

Ultrasound Shear Wave Elastography Evaluation of the Liver and Implications for Perioperative Medicine

Ultrasound shear wave elastography (SWE) is a non-invasive, low risk technology allowing the assessment of tissue stiffness. Used clinically for nearly two decades to diagnose and stage liver fibrosis and cirrhosis, it has recently been appreciated for its ability to differentiate between more subtle forms of liver dysfunction. In this review, we will discuss the principle of ultrasound shear wave elastography, its traditional utilization in grading liver cirrhosis, as well as its evolving role in identifying more subtle degrees of liver injury. Finally, we will show how this capacity to distinguish nuanced changes may provide an opportunity for its use in perioperative risk stratification.

Efficacy, tolerability and pharmacokinetics of survodutide, a glucagon/glucagon-like peptide-1 receptor dual agonist, in cirrhosis

BACKGROUND & AIMS

Survodutide is a glucagon/glucagon-like peptide-1 receptor dual agonist in development for the treatment of metabolic dysfunction-associated steatohepatitis (MASH). We investigated the pharmacokinetic and safety profile of survodutide in people with cirrhosis.

METHODS

This multinational, non-randomized, open-label, phase I clinical trial initially evaluated a single subcutaneous dose of survodutide 0.3 mg in people with Child-Pugh class A, B or C cirrhosis and healthy individuals with or without overweight/obesity matched for age, sex, and weight; the primary endpoints were the area under the plasma concentration-time curve from 0 to infinity (AUC0-∞) and maximal plasma concentration (Cmax). Subsequently, people with overweight/obesity with or without cirrhosis (Child-Pugh class A or B) received once-weekly subcutaneous doses escalated from 0.3 mg to 6.0 mg over 24 weeks then maintained for 4 weeks; the primary endpoint was drug-related treatment-emergent adverse events, with MASH/cirrhosis-related endpoints explored.

RESULTS

In the single-dose cohorts (n = 41), mean AUC0-∞ and Cmax were similar in those with cirrhosis compared with healthy individuals (90% CIs for adjusted geometric mean ratios spanned 1). Drug-related adverse events occurred in 25.0% of healthy individuals and ≤25.0% of those with cirrhosis after single doses, and 82.4% and 87.5%, respectively, of the multiple-dose cohorts (n = 41) over 28 weeks. Liver fat content, liver stiffness, liver volume, body weight, and other hepatic and metabolic disease markers were generally reduced after 28 weeks of survodutide treatment.

CONCLUSIONS

Survodutide is generally tolerable in people with compensated or decompensated cirrhosis, does not require pharmacokinetic-related dose adjustment, and may improve liver-related non-invasive tests, supporting its investigation for MASH-related cirrhosis.

IMPACT AND IMPLICATIONS

Survodutide is a glucagon receptor/glucagon-like peptide-1 receptor dual agonist in development for treatment of metabolic dysfunction-associated steatohepatitis (MASH), which causes cirrhosis in ∼20% of cases. This trial delineates the pharmacokinetic and safety profile of survodutide in people with compensated or decompensated cirrhosis, and revealed associated reductions in liver fat content, markers of liver fibrosis and body weight. These findings have potential relevance for people with MASH-including those with decompensated cirrhosis, who are usually excluded from clinical trials of investigational drugs. Based on this study, further investigation of survodutide for MASH-related cirrhosis is warranted.

CLINICALTRIALS

GOV IDENTIFIER

NCT05296733.

EASL-EASD-EASO Clinical Practice Guidelines on the Management of Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD)

Metabolic dysfunction-associated steatotic liver disease (MASLD), previously termed non-alcoholic fatty liver disease (NAFLD), is defined as steatotic liver disease (SLD) in the presence of one or more cardiometabolic risk factor(s) and the absence of harmful alcohol intake. The spectrum of MASLD includes steatosis, metabolic dysfunction-associated steatohepatitis (MASH, previously NASH), fibrosis, cirrhosis and MASH-related hepatocellular carcinoma (HCC). This joint EASL-EASD-EASO guideline provides an update on definitions, prevention, screening, diagnosis and treatment for MASLD. Case-finding strategies for MASLD with liver fibrosis, using non-invasive tests, should be applied in individuals with cardiometabolic risk factors, abnormal liver enzymes, and/or radiological signs of hepatic steatosis, particularly in the presence of type 2 diabetes (T2D) or obesity with additional metabolic risk factor(s). A stepwise approach using blood-based scores (such as FIB-4) and, sequentially, imaging techniques (such as transient elastography) is suitable to rule-out/in advanced fibrosis, which is predictive of liver-related outcomes. In adults with MASLD, lifestyle modification - including weight loss, dietary changes, physical exercise and discouraging alcohol consumption - as well as optimal management of comorbidities - including use of incretin-based therapies (e.g. semaglutide, tirzepatide) for T2D or obesity, if indicated - is advised. Bariatric surgery is also an option in individuals with MASLD and obesity. If locally approved and dependent on the label, adults with non-cirrhotic MASH and significant liver fibrosis (stage ≥2) should be considered for a MASH-targeted treatment with resmetirom, which demonstrated histological effectiveness on steatohepatitis and fibrosis with an acceptable safety and tolerability profile. No MASH-targeted pharmacotherapy can currently be recommended for the cirrhotic stage. Management of MASH-related cirrhosis includes adaptations of metabolic drugs, nutritional counselling, surveillance for portal hypertension and HCC, as well as liver transplantation in decompensated cirrhosis.

EASL-EASD-EASO Clinical Practice Guidelines on the management of metabolic dysfunction-associated steatotic liver disease (MASLD)

Metabolic dysfunction-associated steatotic liver disease (MASLD), previously termed non-alcoholic fatty liver disease (NAFLD), is defined as steatotic liver disease (SLD) in the presence of one or more cardiometabolic risk factor(s) and the absence of harmful alcohol intake. The spectrum of MASLD includes steatosis, metabolic dysfunction-associated steatohepatitis (MASH, previously NASH), fibrosis, cirrhosis and MASH-related hepatocellular carcinoma (HCC). This joint EASL-EASD-EASO guideline provides an update on definitions, prevention, screening, diagnosis and treatment for MASLD. Case-finding strategies for MASLD with liver fibrosis, using non-invasive tests, should be applied in individuals with cardiometabolic risk factors, abnormal liver enzymes, and/or radiological signs of hepatic steatosis, particularly in the presence of type 2 diabetes (T2D) or obesity with additional metabolic risk factor(s). A stepwise approach using blood-based scores (such as FIB-4) and, sequentially, imaging techniques (such as transient elastography) is suitable to rule-out/in advanced fibrosis, which is predictive of liver-related outcomes. In adults with MASLD, lifestyle modification - including weight loss, dietary changes, physical exercise and discouraging alcohol consumption - as well as optimal management of comorbidities - including use of incretin-based therapies (e.g. semaglutide, tirzepatide) for T2D or obesity, if indicated - is advised. Bariatric surgery is also an option in individuals with MASLD and obesity. If locally approved and dependent on the label, adults with non-cirrhotic MASH and significant liver fibrosis (stage ≥2) should be considered for a MASH-targeted treatment with resmetirom, which demonstrated histological effectiveness on steatohepatitis and fibrosis with an acceptable safety and tolerability profile. No MASH-targeted pharmacotherapy can currently be recommended for the cirrhotic stage. Management of MASH-related cirrhosis includes adaptations of metabolic drugs, nutritional counselling, surveillance for portal hypertension and HCC, as well as liver transplantation in decompensated cirrhosis.

Incretin and glucagon receptor polypharmacology in chronic kidney disease

Chronic kidney disease is a debilitating condition associated with significant morbidity and mortality. In recent years, the kidney effects of incretin-based therapies, particularly glucagon-like peptide-1 receptor agonists (GLP-1RAs), have garnered substantial interest in the management of type 2 diabetes and obesity. This review delves into the intricate interactions between the kidney, GLP-1RAs, and glucagon, shedding light on their mechanisms of action and potential kidney benefits. Both GLP-1 and glucagon, known for their opposing roles in regulating glucose homeostasis, improve systemic risk factors affecting the kidney, including adiposity, inflammation, oxidative stress, and endothelial function. Additionally, these hormones and their pharmaceutical mimetics may have a direct impact on the kidney. Clinical studies have provided evidence that incretins, including those incorporating glucagon receptor agonism, are likely to exhibit improved kidney outcomes. Although further research is necessary, receptor polypharmacology holds promise for preserving kidney function through eliciting vasodilatory effects, influencing volume and electrolyte handling, and improving systemic risk factors.

The role of glucagon-like peptide-1 receptor agonists in metabolic dysfunction-associated steatohepatitis

Despite its considerable and growing burden, there are currently no Food and Drug Administration-approved treatments for metabolic dysfunction-associated steatotic liver disease or its progressive form, metabolic dysfunction-associated steatohepatitis (MASH). Several glucagon-like peptide-1 receptor agonists (GLP-1RAs) and other agents are in various phases of clinical development for use in MASH; an ideal therapy should reduce liver fat content, improve chronic liver disease, help mitigate metabolic comorbidities and decrease all-cause mortality. Because of interconnected disease mechanisms, metabolic dysfunction-associated steatotic liver disease/MASH often coexists with type 2 diabetes (T2D), obesity and cardiovascular disease. Various GLP-1RAs are Food and Drug Administration-approved for use in T2D, and two, liraglutide and semaglutide, are approved for overweight and obesity. GLP-1RAs decrease glucose levels and body weight and improve cardiovascular outcomes in people with T2D who are at high risk of cardiovascular disease. In addition, GLP-1RAs have been reported to reduce liver fat content and liver enzymes, reduce oxidative stress and improve hepatic de novo lipogenesis and the histopathology of MASH. Weight loss may contribute to these effects; however, the exact mechanisms are unknown. Adverse events that are commonly associated with GLP-1RAs include vomiting, nausea and diarrhoea. There is a lack of evidence from meta-analyses regarding the increased risk of acute pancreatitis and various forms of cancer with GLP-1RAs. Large-scale, phase 3 trials, which will provide definitive data on GLP-1RAs and other potential therapies in MASH, are ongoing. Given the spectrum of modalities under investigation, it is hoped that these trials will support the identification of pharmacotherapies that provide clinical benefit for patients with MASH.

Pharmacotherapeutic options for metabolic dysfunction-associated steatotic liver disease: where are we today?

INTRODUCTION

Metabolic dysfunction-associated steatotic liver disease (MASLD) is defined by hepatic steatosis and cardiometabolic risk factors like obesity, type 2 diabetes, and dyslipidemia. Persistent metabolic injury may promote inflammatory processes resulting in metabolic dysfunction-associated steatohepatitis (MASH) and liver fibrosis. Mechanistic insights helped to identify potential drug targets, thereby supporting the development of novel compounds modulating disease drivers.

AREAS COVERED

The U.S. Food and Drug Administration has recently approved the thyroid hormone receptor β-selective thyromimetic resmetirom as the first compound to treat MASH and liver fibrosis. This review provides a comprehensive overview of current and potential future pharmacotherapeutic options and their modes of action. Lessons learned from terminated clinical trials are discussed together with the first results of trials investigating novel combinational therapeutic approaches.

EXPERT OPINION

Approval of resmetirom as the first anti-MASH agent may revolutionize the therapeutic landscape. However, long-term efficacy and safety data for resmetirom are currently lacking. In addition, heterogeneity of MASLD reflects a major challenge to define effective agents. Several lead compounds demonstrated efficacy in reducing obesity and hepatic steatosis, while anti-inflammatory and antifibrotic effects of monotherapy appear less robust. Better mechanistic understanding, exploration of combination therapies, and patient stratification hold great promise for MASLD therapy.

MetALD: Does it require a different therapeutic option?

New guidelines for the definitions of steatotic liver disease have named the entity of metabolic dysfunction and alcohol-associated liver disease (MetALD) as an overlap condition of metabolic dysfunction-associated steatotic liver disease (MASLD) and alcohol-associated liver disease. There is a broad range of therapeutics in all stages of development for MASLD, but these therapeutics, in general, have not been studied in patients with significant ongoing alcohol use. In this review, we discuss the current understanding of the endogenous and exogenous risks for MASLD and MetALD. Rational strategies for therapeutic intervention in MetALD include biopsychosocial interventions, alcohol use cessation strategies, including the use of medications for alcohol use disorder, and judicious use of therapeutics for steatotic liver disease. Therapeutics with promise for MetALD include incretin-based therapies, FGF21 agonists, thyroid hormone receptor beta agonists, sodium-glucose co-transporter 2 inhibitors, and agents to modify de novo lipogenesis. Currently, glucagon-like peptide 1 receptor agonists and peroxisome proliferator-activated receptor γ agonists have the largest body of literature supporting their use in MASLD, and there is a paucity of agents in trials for alcohol-associated liver disease. From existing studies, it is not clear if unique therapeutics or a combinatorial approach are needed for MetALD. Further elucidation of the safety and benefits of MASLD-related therapies is of paramount importance for advancing therapeutics for MetALD in carefully designed inclusive clinical trials.

Role of incretins and glucagon receptor agonists in metabolic dysfunction-associated steatotic liver disease: Opportunities and challenges

Metabolic dysfunction-associated steatotic liver disease (MASLD) has become the most common chronic liver disease worldwide, paralleling the rising pandemic of obesity and type 2 diabetes. Due to the growing global health burden and complex pathogenesis of MASLD, a multifaceted and innovative therapeutic approach is needed. Incretin receptor agonists, which were initially developed for diabetes management, have emerged as promising candidates for MASLD treatment. This review describes the pathophysiological mechanisms and action sites of three major classes of incretin/glucagon receptor agonists: glucagon-like peptide-1 receptor agonists, glucose-dependent insulinotropic polypeptide receptor agonists, and glucagon receptor agonists. Incretins and glucagon directly or indirectly impact various organs, including the liver, brain, pancreas, gastrointestinal tract, and adipose tissue. Thus, these agents significantly improve glycemic control and weight management and mitigate MASLD pathogenesis. Importantly, this study provides a summary of clinical trials analyzing the effectiveness and safety of incretin receptor agonists in MASLD management and provides an in-depth analysis highlighting their beneficial effects on improving liver function, hepatic steatosis, and intrahepatic inflammation. There are emerging challenges associated with the use of these medications in the real world, particularly adverse events, drug-drug interactions, and barriers to access, which are discussed in detail. Additionally, this review highlights the evolving role of incretin receptor agonists in MASLD management and suggests future research directions.

Oral glucagon-like peptide-1 receptor agonists and combinations of entero-pancreatic hormones as treatments for adults with type 2 diabetes: where are we now?

INTRODUCTION

Glucagon-like peptide-1 (GLP-1) receptor agonists (RAs) have changed the landscape of type 2 diabetes (T2D) management due to their cardio-renal benefits, their glucose-lowering efficacy and weight loss (WL) maintenance. However, the response to GLP-1 RA monotherapy is heterogeneous. Additionally, the majority of GLP-1 RAs are injectable treatments. Oral GLP-1 RAs and injectable combinations of GLP-1 with other entero-pancreatic hormones (glucose-dependent insulinotropic polypeptide (GIP), glucagon and amylin) are under development for T2D and obesity management.

AREAS COVERED

Herein, we review the data on (i) oral GLP-1 RAs (oral semaglutide 25/50 mg and orforglipron) and (ii) dual/triple agonists (tirzepatide, cagrilintide 2.4 mg/semaglutide 2.4 mg, survodutide, mazdutide, retatrutide) that have recently completed phase 3 trials for T2D or are currently in phase 3 clinical trials. Tirzepatide is the first approved dual agonist (GLP-1/GIP) for T2D and obesity management.

EXPERT OPINION

We are in a new era in T2D management where entero-pancreatic hormone-based treatments can result in ≥15% WL and euglycemia for many people with T2D. Multiple molecules with different mechanisms of action are under development for T2D, obesity and other metabolic complications. Data on their cardio-renal benefits, long-term efficacy and safety as well as their cost-effectiveness will better inform their position in treatment algorithms.

Dietary and pharmacological treatment in patients with metabolic-dysfunction associated steatotic liver disease

Metabolic-dysfunction Associated Steatotic Liver Disease (MASLD) is a disease spectrum encompassing liver injury with progressive severity, tightly connected to the metabolic syndrome. Management of MASLD mostly relies on lifestyle change aiming at improving metabolic homeostasis and insulin resistance. A Mediterranean-like dietary pattern and individualized lifestyle interventions are the cornerstone of MASLD treatment. A careful evaluation of alcohol intake and active treatment of all metabolic co-morbidities are recommended. In the MASLD spectrum, the population with liver inflammation and enhanced fibrogenesis (MASH - Metabolic-dysfunction associated steatohepatitis) can progress to advanced liver disease and has been addressed as "at-risk MASH", eligible to pharmacological treatment according to FDA and EMA. Currently there is a robust therapeutic pipeline across a variety of new targets to resolve MASH or reverse fibrosis, or both. Some of these therapies have beneficial effects that extend beyond the liver, such as effects on glycaemic control, lipid profile and weight loss. For "at-risk" MASH, reversal of fibrosis by one stage or resolution of MASH with no worsening in fibrosis as a surrogate end-point will need to be accompanied by overall survival benefits. In this review, we summarize the current evidence on lifestyle interventions in MASLD as well as pharmacological approaches for fibrosing MASH that have progressed to phase II and phase III clinical trials.

Glucagon-like Peptide 1, Glucose-Dependent Insulinotropic Polypeptide, and Glucagon Receptor Agonists in Metabolic Dysfunction-Associated Steatotic Liver Disease: Novel Medication in New Liver Disease Nomenclature

Glucagon-like peptide 1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) are incretins that regulate postprandial glucose regulation, stimulating insulin secretion from pancreatic β-cells in response to food ingestion. Modified GLP-1 receptor agonists (GLP-1RAs) are being administered for the treatment of obesity and type 2 diabetes mellitus (T2DM). Strongly related to those disorders, metabolic dysfunction-associated steatotic liver disease (MASLD), especially its aggressive form, defined as metabolic dysfunction-associated steatohepatitis (MASH), is a major healthcare burden associated with high morbidity and extrahepatic complications. GLP-1RAs have been explored in MASH patients with evident improvement in liver dysfunction enzymes, glycemic control, and weight loss. Importantly, the combination of GLP-1RAs with GIP and/or glucagon RAs may be even more effective via synergistic mechanisms in amelioration of metabolic, biochemical, and histological parameters of MASLD but also has a beneficial impact on MASLD-related complications. In this current review, we aim to provide an overview of incretins' physiology, action, and signaling. Furthermore, we provide insight into the key pathophysiological mechanisms through which they impact MASLD aspects, as well as we analyze clinical data from human interventional studies. Finally, we discuss the current challenges and future perspectives pertinent to this growing area of research and clinical medicine.

MASH clinical trials and drugs pipeline: An impending tsunami

Metabolic dysfunction-associated steatotic liver disease, formerly known as NAFLD, has ascended to prominence as the predominant chronic liver disease in Western countries and now stands as a leading cause of liver transplantations. In the more advanced stage, metabolic dysfunction-associated steatohepatitis (MASH) may lead to fibrosis, a gateway to cirrhosis, liver cancer, and liver failure. Despite extensive research and exploration of various drug mechanisms, the anticipation for the inaugural approved drug to materialize by 2024 is palpable, marking a significant milestone. Numerous pathways have been investigated for MASH treatment, exploring thyroid hormone receptors, glucagon-like peptides 1, peroxisome proliferator-activated receptors, and agents influencing hepatic steatosis synthesis, inflammatory pathways, genetic components, fibrosis mechanisms, and an array of other avenues. Over time, key regulatory directions have crystallized, now manifesting in 2 primary endpoints under investigation: resolution of steatohepatitis without worsening fibrosis and/or improvement of fibrosis stage without worsening of steatohepatitis, especially used in phase 3 clinical trials, while alternative noninvasive endpoints are explored in phase 2 trials. The prospect of proving efficacy in clinical trials opens doors to combination therapies, evaluating the ideal combination of drugs to yield comprehensive benefits, extending beyond the liver to other organs. Certain combination drug trials are already underway. In this review, we discuss the forefront of MASH drug research as of 2023/2024, illuminating mechanisms, outcomes, and future trajectories. Furthermore, we tackle the challenges confronting MASH trials and propose potential strategies for surmounting them.

Letter: Severe underweight and sarcopenia in decompensated cirrhosis are associated with high FGF21 levels

This article is linked to Alkhouri et al papers. To view these articles, visit https://doi.org/10.1111/apt.17709 and https://doi.org/10.1111/apt.17907

The Road towards Triple Agonists: Glucagon-Like Peptide 1, Glucose-Dependent Insulinotropic Polypeptide and Glucagon Receptor - An Update

Obesity is the fifth leading risk factor for global deaths with numbers continuing to increase worldwide. In the last 20 years, the emergence of pharmacological treatments for obesity based on gastrointestinal hormones has transformed the therapeutic landscape. The successful development of glucagon-like peptide-1 (GLP-1) receptor agonists, followed by the synergistic combined effect of glucose-dependent insulinotropic polypeptide (GIP)/GLP-1 receptor agonists achieved remarkable weight loss and glycemic control in those with the diseases of obesity and type 2 diabetes. The multiple cardiometabolic benefits include improving glycemic control, lipid profiles, blood pressure, inflammation, and hepatic steatosis. The 2023 phase 2 double-blind, randomized controlled trial evaluating a GLP-1/GIP/glucagon receptor triagonist (retatrutide) in patients with the disease of obesity reported 24.2% weight loss at 48 weeks with 12 mg retatrutide. This review evaluates the current available evidence for GLP-1 receptor agonists, dual GLP-1/GIP receptor co-agonists with a focus on GLP-1/GIP/glucagon receptor triagonists and discusses the potential future benefits and research directions.

Mechanisms of action of incretin receptor based dual- and tri-agonists in pancreatic islets

Simultaneous activation of the incretin G-protein-coupled receptors (GPCRs) via unimolecular dual-receptor agonists (UDRA) has emerged as a new therapeutic approach for type 2 diabetes. Recent studies also advocate triple agonism with molecules also capable of binding the glucagon receptor. In this scoping review, we discuss the cellular mechanisms of action (MOA) underlying the actions of these novel and therapeutically important classes of peptide receptor agonists. Clinical efficacy studies of several UDRAs have demonstrated favorable results both as monotherapies and when combined with approved hypoglycemics. Although the additive insulinotropic effects of dual glucagon-like peptide-1 receptor (GLP-1R) and glucose-dependent insulinotropic peptide receptor (GIPR) agonism were anticipated based on the known actions of either glucagon-like peptide-1 (GLP-1) or glucose-dependent insulinotropic peptide (GIP) alone, the additional benefits from GCGR were largely unexpected. Whether additional synergistic or antagonistic interactions among these G-protein receptor signaling pathways arise from simultaneous stimulation is not known. The signaling pathways affected by dual- and tri-agonism require more trenchant investigation before a comprehensive understanding of the cellular MOA. This knowledge will be essential for understanding the chronic efficacy and safety of these treatments.