LY3298176, a novel dual GIP and GLP-1 receptor agonist for the treatment of type 2 diabetes mellitus: From discovery to clinical proof of concept

Nephroprotective Properties of the Glucose-Dependent Insulinotropic Polypeptide (GIP) and Glucagon-like Peptide-1 (GLP-1) Receptor Agonists

Diabetes mellitus is the leading cause of chronic kidney disease, and about 30–40% of patients with diabetes will develop kidney disease. Incretin hormones have received attention during the past three decades not only as a pharmacotherapy for the treatment of type 2 diabetes, but also for their cardiorenometabolic effects. The main incretins are glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP). Additional to the pancreas, receptors for GLP-1 are widely distributed in various organs, causing positive effects on endothelial function and vascular atherogenesis. Along with glycemic control and weight reduction, GLP-1 receptor agonists also strongly improve cardiovascular and renal outcomes in patients with type 2 diabetes. Recently, a dual GIP and GLP-1 receptor agonist has been approved for the treatment of type 2 diabetes. Compared to GLP-1 receptor agonist semaglutide, dual GIP and GLP-1 receptor agonist tirzepatide showed a superior reduction in hemoglobin A1c and body weight. Preliminary results also suggest that tirzepatide improves kidney outcomes in adults with type 2 diabetes with increased cardiovascular risk. In this review, we present the nephroprotective properties of dual GIP and GLP-1 receptor agonists as a new drug to treat type 2 diabetes.

The Impact of Exposure Profile on the Efficacy of Dual Amylin and Calcitonin Receptor Agonist Therapy

Background: Dual Amylin and Calcitonin Receptor Agonists (DACRAs) are treatment candidates for obesity and type 2 diabetes. Recently, a once-weekly DACRA (KBP-A) showed promise, potentially due to its different exposure profile compared to daily DACRA (KBP). Parathyroid hormone, a G-protein-coupled receptor (GPCR) class B agonist, is an example of the exposure profile being critical to the effect. Since KBP and KBP-A also activate GPCR class B, we compared the effects of injection to continuous infusion of short-acting KBP and long-acting KBP-A in obese and diabetic rats to shed light on the role of exposure profiles. Methods: To explore the metabolic benefits of dose optimization, the following dosing profiles were compared in High Fat Diet (HFD)-fed Sprague–Dawley rats and diabetic Zucker Diabetic Fatty (ZDF) rats: (1) KBP dosed once-daily by injection or by continuous infusion in HFD and ZDF rats; (2) KBP injected once-daily and KBP-A injected once every 3rd day (Q3D) in HFD rats; (3) KBP-A injected Q3D or by infusion in ZDF rats. Results: KBP and KBP-A, delivered by either injection or infusion, resulted in similar weight and food intake reductions in HFD rats. In ZDF rats, injection of KBP improved glucose control significantly compared to infusion, while delivery of KBP-A by injection and continuous infusion was comparable in terms of glucose control. Conclusion: different dosing profiles of KBP and KBP-A had no impact on metabolic benefits in HFD rats. In diabetic ZDF rats, KBP by injection instead of infusion was superior, while for KBP-A the effects were similar.

Novel Therapies for Cardiometabolic Disease: Recent Findings in Studies with Hormone Peptide-Derived G Protein Coupled Receptor Agonists

The increasing prevalence of obesity and type 2 diabetes (T2DM) is provoking an important socioeconomic burden mainly in the form of cardiovascular disease (CVD). One successful strategy is the so-called metabolic surgery whose beneficial effects are beyond dietary restrictions and weight loss. One key underlying mechanism behind this surgery is the cooperative improved action of the preproglucagon-derived hormones, glucagon, glucagon-like peptide-1 (GLP-1), and glucose-dependent insulinotropic polypeptide (GIP) which exert their functions through G protein-coupled receptors (GPCR). Great success has been reached with therapies based on the GLP-1 receptor monoagonism; therefore, a logical and rational approach is the use of the dual and triagonism of GCPC to achieve complete metabolic homeostasis. The present review describes novel findings regarding the complex biology of the preproglucagon-derived hormones, their signaling, and the drug development of their analogues, especially those acting as dual and triagonists. Moreover, the main investigations into animal models and ongoing clinical trials using these unimolecular dual and triagonists are included which have demonstrated their safety, efficacy, and beneficial effects on the CV system. These therapeutic strategies could greatly impact the treatment of CVD with unprecedented benefits which will be revealed in the next years.

LY3437943, a novel triple glucagon, GIP, and GLP-1 receptor agonist for glycemic control and weight loss: From discovery to clinical proof of concept

With an increasing prevalence of obesity, there is a need for new therapies to improve body weight management and metabolic health. Multireceptor agonists in development may provide approaches to fulfill this unmet medical need. LY3437943 is a novel triple agonist peptide at the glucagon receptor (GCGR), glucose-dependent insulinotropic polypeptide receptor (GIPR), and glucagon-like peptide-1 receptor (GLP-1R). In vitro, LY3437943 shows balanced GCGR and GLP-1R activity but more GIPR activity. In obese mice, administration of LY3437943 decreased body weight and improved glycemic control. Body weight loss was augmented by the addition of GCGR-mediated increases in energy expenditure to GIPR- and GLP-1R-driven calorie intake reduction. In a phase 1 single ascending dose study, LY3437943 showed a safety and tolerability profile similar to other incretins. Its pharmacokinetic profile supported once-weekly dosing, and a reduction in body weight persisted up to day 43 after a single dose. These findings warrant further clinical assessment of LY3437943.

Tirzepatide, a dual GIP/GLP-1 receptor co-agonist for the treatment of type 2 diabetes with unmatched effectiveness regrading glycaemic control and body weight reduction

Tirzepatide is the first dual GIP/GLP-1 receptor co-agonist approved for the treatment of type 2 diabetes in the USA, Europe, and the UAE. Tirzepatide is an acylated peptide engineered to activate the GIP and GLP-1 receptors, key mediators of insulin secretion that are also expressed in regions of the brain that regulate food intake. Five clinical trials in type 2-diabetic subjects (SURPASS 1–5) have shown that tirzepatide at 5–15 mg per week reduces both HbA_1c (1.24 to 2.58%) and body weight (5.4–11.7 kg) by amounts unprecedented for a single agent. A sizable proportion of patients (23.0 to 62.4%) reached an HbA_1c of < 5.7% (which is the upper limit of the normal range indicating normoglycaemia), and 20.7 to 68.4% lost more than 10% of their baseline body weight. Tirzepatide was significantly more effective in reducing HbA_1c and body weight than the selective GLP-1 RA semaglutide (1.0 mg per week), and titrated basal insulin. Adverse events related to tirzepatide were similar to what has been reported for selective GLP-1RA, mainly nausea, vomiting, diarrhoea, and constipation, that were more common at higher doses. Cardiovascular events have been adjudicated across the whole study program, and MACE-4 (nonfatal myocardial infarction, non-fatal stroke, cardiovascular death and hospital admission for angina) events tended to be reduced over up to a 2 year-period, albeit with low numbers of events. For none of the cardiovascular events analysed (MACE-4, or its components) was a hazard ratio > 1.0 vs. pooled comparators found in a meta-analysis covering the whole clinical trial program, and the upper bounds of the confidence intervals for MACE were < 1.3, fulfilling conventional definitions of cardiovascular safety. Tirzepatide was found to improve insulin sensitivity and insulin secretory responses to a greater extent than semaglutide, and this was associated with lower prandial insulin and glucagon concentrations. Both drugs caused similar reductions in appetite, although tirzepatide caused greater weight loss. While the clinical effects of tirzepatide have been very encouraging, important questions remain as to the mechanism of action. While GIP reduces food intake and body weight in rodents, these effects have not been demonstrated in humans. Moreover, it remains to be shown that GIPR agonism can improve insulin secretion in type 2 diabetic patients who have been noted in previous studies to be unresponsive to GIP. Certainly, the apparent advantage of tirzepatide, a dual incretin agonist, over GLP-1RA will spark renewed interest in the therapeutic potential of GIP in type 2 diabetes, obesity and related co-morbidities.

Efficacy and safety of tirzepatide monotherapy compared with dulaglutide in Japanese patients with type 2 diabetes (SURPASS J-mono): a double-blind, multicentre, randomised, phase 3 trial

BACKGROUND

As the disease progresses, many patients with type 2 diabetes have difficulty in reaching treatment goals. We aimed to assess the efficacy and safety of tirzepatide, a novel GIP and GLP-1 receptor agonist, compared with dulaglutide in Japanese patients with type 2 diabetes.

METHODS

This multicentre, randomised, double-blind, parallel, active-controlled, phase 3 trial was conducted in 46 medical research centres and hospitals in Japan. Adults aged 20 years or older with type 2 diabetes who had discontinued oral antihyperglycaemic monotherapy or were treatment-naïve were included. Participants were randomly assigned (1:1:1:1) to receive tirzepatide (5, 10, or 15 mg) or dulaglutide (0·75 mg) once per week using a computer-generated random sequence with an Interactive Web Response System. Participants were stratified based on baseline HbA_1c (≤8·5% or >8·5%), baseline BMI (<25 or ≥25 kg/m²), and washout of antidiabetic medication. Participants, investigators, and the sponsor were masked to treatment assignment. The starting dose of tirzepatide was 2·5 mg once per week for 4 weeks, which was then increased to 5 mg in the tirzepatide 5 mg treatment group. For the tirzepatide 10 and 15 mg treatment groups, increases by 2·5 mg occurred once every 4 weeks until the assigned dose was reached. The primary endpoint was mean change in HbA_1c from baseline at week 52 measured in the modified intention-to-treat population. This trial is registered with ClinicalTrials.gov, NCT03861052.

FINDINGS

Between May 7, 2019, and March 31, 2021, 821 participants were assessed for study eligibility and 636 were randomly assigned to receive at least one dose of tirzepatide 5 mg (n=159), 10 mg (n=158), or 15 mg (n=160), or dulaglutide 0·75 mg (n=159). 615 (97%) participants completed the study and 21 (3%) discontinued. Participants had a mean age of 56·6 years (SD 10·3) and were mostly male (481 [76%]). At week 52, HbA_1c decreased from baseline by a least squares mean of -2·4 (SE 0·1) for tirzepatide 5 mg, -2·6 (0·1) for tirzepatide 10 mg, -2·8 (0·1) for tirzepatide 15 mg, and -1·3 (0·1) for dulaglutide. Estimated mean treatment differences versus dulaglutide were -1·1 (95% CI -1·3 to -0·9) for tirzepatide 5 mg, -1·3 (-1·5 to -1·1) for tirzepatide 10 mg, and -1·5 (-1·71 to -1·4) for tirzepatide 15 mg (all p<0·0001). Tirzepatide was associated with dose-dependent reductions in bodyweight with a least square mean difference of -5·8 kg (SE 0·4; -7·8% reduction) for 5 mg, -8·5 kg (0·4; -11·0% reduction) for 10 mg, and -10·7 kg (0·4; -13·9% reduction) for 15 mg of tirzepatide compared with -0·5 kg (0·4; -0·7% reduction) for dulaglutide. The most common treatment-emergent adverse events were nausea (19 [12%] participants in the 5 mg group vs 31 [20%] in the 10 mg group vs 32 [20%] in the 15 mg group all receiving tirzepatide vs 12 (8%) in the group receiving dulaglutide), constipation (24 [15%] vs 28 [18%] vs 22 [14%] vs 17 [11%]), and nasopharyngitis (29 [18%] vs 25 [16%] vs 22 [14%] vs 26 [16%]). The most frequent adverse events were gastrointestinal (23 [4%] of 636).

INTERPRETATION

Tirzepatide was superior compared with dulaglutide for glycaemic control and reduction in bodyweight. The safety profile of tirzepatide was consistent with that of GLP-1 receptor agonists, indicating a potential therapeutic use in Japanese patients with type 2 diabetes.

FUNDING

Eli Lilly and Company.

TRANSLATION

For the Japanese translation of the abstract see Supplementary Materials section.

Tirzepatide: Does the Evidence to Date Show Potential for the Treatment of Early Stage Type 2 Diabetes?

Tirzepatide is a novel “twincretin” with glucagon-like peptide 1 and glucose-dependent insulinotropic polypeptide receptor agonist activity, which was recently approved by the Food and Drug Administration for the treatment of type 2 diabetes mellitus. In this review, we discuss preclinical and mechanistic human studies, which demonstrate improvements in insulin sensitivity and beta-cell function with the use of tirzepatide, as compared to placebo and glucagon-like peptide 1 receptor agonists. We then discuss SURPASS trials 1–5, which evaluated the safety and efficacy of tirzepatide for type 2 diabetes mellitus as either monotherapy or combination therapy with other antidiabetic agents. The magnitude of tirzepatide’s effects and the efficacy relative to other anti-diabetes medications on weight, glycemic control, and beta-cell function may prove beneficial for the treatment of early type 2 diabetes mellitus. Further studies, including data on cardiovascular outcomes and long-term safety, will continue to elucidate the role of tirzepatide in the treatment algorithm of type 2 diabetes mellitus.

Safety and efficacy of tirzepatide as an add-on to single oral antihyperglycaemic medication in patients with type 2 diabetes in Japan (SURPASS J-combo): a multicentre, randomised, open-label, parallel-group, phase 3 trial

BACKGROUND

Due to potential ethnic differences in the pathophysiology of type 2 diabetes, new therapeutics need to be evaluated in Japanese patients. We aimed to assess the safety and glycaemic efficacy of tirzepatide as an add-on treatment in Japanese patients with type 2 diabetes who had inadequate glycaemic control with stable doses of various oral antihyperglycaemic monotherapies.

METHODS

This multicentre, open-label, parallel-group, randomised, phase 3 trial was conducted at 34 medical research centres and hospitals in Japan. Eligible participants were aged 20 years or older with inadequately controlled (HbA_1c ≥7·0% to <11·0%) type 2 diabetes and were receiving oral antihyperglycaemic monotherapy (sulfonylureas, biguanides, α-glucosidase inhibitors, thiazolidinedione, glinides, or SGLT2 inhibitors) for at least 3 months (stable dose for ≥8 weeks before screening), had a BMI of 23 kg/m² or higher, and stable bodyweight (±5%) for at least 3 months before screening. After a 2-week screening and 2-week lead-in period, all participants were randomly assigned (1:1:1) to receive 5, 10, or 15 mg of tirzepatide, administered once per week subcutaneously for 52 weeks followed by a 4 week safety follow-up period, using a computer-generated random sequence and interactive web response system, stratified by oral antihyperglycaemic medication group. All participants started receiving 2·5 mg tirzepatide and doses were escalated by 2·5 mg every 4 weeks until the assigned dose was reached. The primary endpoint was safety and tolerability during 52 weeks of treatment, assessed as incidence of treatment-emergent adverse events in the modified intention-to-treat (mITT) population. This trial is registered with ClinicalTrials.gov, NCT03861039.

FINDINGS

Between March 30, 2019, and Feb 16, 2021, with recruitment and enrolment continuing until Feb 4, 2020, 484 participants were assessed for eligibility and 443 were randomly assigned to receive at least one dose of tirzepatide (148 [33%] in the 5 mg group, 147 [33%] in the 10 mg group, and 148 [33%] in the 15 mg group). 398 (90%) participants completed the study and treatment. Most participants (343 [77%] of 443) had at least one treatment-emergent adverse event. Treatment-emergent adverse events were more frequent in the tirzepatide 15 mg group (125 [84%] of 148) than the 5 mg (109 [74%] of 148) and 10 mg groups (109 [74%] of 147). The most frequent treatment-emergent adverse events with tirzepatide were mild or moderate nasopharyngitis (75 [17%]), nausea (74 [17%]), constipation (54 [12%]), diarrhoea (51 [12%]), and decreased appetite (44 [10%]). At week 52, mean changes from baseline in bodyweight were -3·8 kg (SE 0·5; -5·1% reduction) in the 5 mg group, -7·5 kg (0·5; -10·1% reduction) in the 10 mg group, and -10·2 kg (0·5; -13·2% reduction) in the 15 mg group. Least squares mean HbA_1c at baseline reduced from 8·5% (SE 0·1) to 6·0% (0·1) in the 5 mg tirzepatide group, from 8·6% (0·1) to 5·6% (0·1) in the 10 mg group, and from 8·6% (0·1) to 5·6% (0·1) in the 15 mg group at week 52. No adjudication-confirmed deaths were reported.

INTERPRETATION

Tirzepatide was well tolerated as an add-on to oral antihyperglycaemic monotherapy in Japanese participants with type 2 diabetes and showed improvement in glycaemic control and bodyweight, irrespective of background oral antihyperglycaemic medication. Tirzepatide is a potential new treatment option for Japanese patients with type 2 diabetes that is inadequately controlled with single oral antihyperglycaemic medication.

FUNDING

Eli Lilly and Company.

TRANSLATION

For the Japanese translation of the abstract see Supplementary Materials section.

GLP-1 Agonist to Treat Obesity and Prevent Cardiovascular Disease: What Have We Achieved so Far?

PURPOSE OF REVIEW

To discuss evidence supporting the use of glucagon-like peptide 1 receptor agonists (GLP-1RA) to treat obesity and their role as a cardioprotective drug. Obesity is not just a hypertrophy of the adipose tissue because it may become dysfunctional and inflamed resulting in increased insulin resistance. Being overweight is associated with increased incidence of cardiovascular events and weight loss achieved through lifestyle changes lowers risk factors, but has no clear effect on cardiovascular outcomes. In contrast, treating obesity with GLP-1RA decreases cardiovascular risk and the possible mechanisms of cardioprotection achieved by this class of drugs are discussed. GLP-1RA were initially developed to treat type 2 diabetes patients, in whom the effects upon glycemia and, moreover, weight loss, especially with long-acting GLP-1RA, were evident. However, cardiovascular safety trials in type 2 diabetes patients, the majority presenting cardiovascular disease and excess weight, showed that GLP-1 receptor agonists were indeed capable of decreasing cardiovascular risk.

RECENT FINDINGS

Type 2 diabetes treatment with GLP-1RA liraglutide and semaglutide paved way to a ground-breaking therapy specific for obesity, as shown with the SCALE 3 mg/day liraglutide program and the STEP 2.4 mg/week semaglutide program. A novel molecule with superior performance is tirzepatide, a GLP-1 and GIP (Gastric Inhibitory Peptide) receptor agonist and recent results from the SURPASS and SURMOUNT programs are briefly described. Liraglutide was approved without a CVOT (Cardiovascular Outcome Trial) because authorities accepted the results from the LEADER study, designed for superiority. The SELECT study with semaglutide will report results only in 2023 and tirzepatide is being tested in patients with diabetes in the SURPASS-CVOT. Clinical studies highlight that GLP-1RA to treat obesity, alongside their concomitant cardioprotective effects, have become a hallmark in clinical science.

Potential of a glucagon-like peptide-1 receptor/glucose-dependent insulinotropic polypeptide receptor/glucagon receptor triagonist for the treatment of obesity and type 2 diabetes

Triagonists of GLP-1R/ GIPR /GCGR, including SAR441255, bind to each receptor and induce specific effects through each receptor signaling pathway, thus result in weight loss and glycemic control in obese T2D animal models.

Signaling pathways in obesity: mechanisms and therapeutic interventions

Obesity is a complex, chronic disease and global public health challenge. Characterized by excessive fat accumulation in the body, obesity sharply increases the risk of several diseases, such as type 2 diabetes, cardiovascular disease, and nonalcoholic fatty liver disease, and is linked to lower life expectancy. Although lifestyle intervention (diet and exercise) has remarkable effects on weight management, achieving long-term success at weight loss is extremely challenging, and the prevalence of obesity continues to rise worldwide. Over the past decades, the pathophysiology of obesity has been extensively investigated, and an increasing number of signal transduction pathways have been implicated in obesity, making it possible to fight obesity in a more effective and precise way. In this review, we summarize recent advances in the pathogenesis of obesity from both experimental and clinical studies, focusing on signaling pathways and their roles in the regulation of food intake, glucose homeostasis, adipogenesis, thermogenesis, and chronic inflammation. We also discuss the current anti-obesity drugs, as well as weight loss compounds in clinical trials, that target these signals. The evolving knowledge of signaling transduction may shed light on the future direction of obesity research, as we move into a new era of precision medicine.

Biased Agonism and Polymorphic Variation at the GLP-1 Receptor: Implications for the Development of Personalised Therapeutics

Glucagon-like peptide-1 receptor (GLP-1R) is a well-studied incretin hormone receptor and target of several therapeutic drugs for type 2 diabetes (T2D), obesity and, more recently, cardiovascular disease. Some signalling pathways downstream of GLP-1R may be responsible for drug adverse effects such as nausea, while others mediate therapeutic outcomes of incretin-based T2D therapeutics. Understanding the interplay between different factors that alter signalling, trafficking, and receptor activity, including biased agonism, single nucleotide polymorphisms and structural modifications is key to develop the next-generation of personalised GLP-1R agonists. However, these interactions remain poorly described, especially for novel therapeutics such as dual and tri-agonists that target more than one incretin receptor. Comparison of GLP-1R structures in complex with G proteins and different peptide and non-peptide agonists has revealed novel insights into important agonist-residue interactions and networks crucial for receptor activation, recruitment of G proteins and engagement of specific signalling pathways. Here, we review the latest knowledge on GLP-1R structure and activation, providing structural evidence for biased agonism and delineating important networks associated with this phenomenon. We survey current biased agonists and multi-agonists at different stages of development, highlighting possible challenges in their translational potential. Lastly, we discuss findings related to non-synonymous genomic variants of GLP1R and the functional importance of specific residues involved in GLP-1R function. We propose that studies of GLP-1R polymorphisms, and specifically their effect on receptor dynamics and pharmacology in response to biased agonists, could have a significant impact in delineating precision medicine approaches and development of novel therapeutics.

Circadian rhythms and pancreas physiology: A review

Type 2 diabetes mellitus, obesity and metabolic syndrome are becoming more prevalent worldwide and will present an increasingly challenging burden on healthcare systems. These interlinked metabolic abnormalities predispose affected individuals to a plethora of complications and comorbidities. Furthermore, diabetes is estimated by the World Health Organization to have caused 1.5 million deaths in 2019, with this figure projected to rise in coming years. This highlights the need for further research into the management of metabolic diseases and their complications. Studies on circadian rhythms, referring to physiological and behavioral changes which repeat approximately every 24 hours, may provide important insight into managing metabolic disease. Epidemiological studies show that populations who are at risk of circadian disruption such as night shift workers and regular long-haul flyers are also at an elevated risk of metabolic abnormalities such as insulin resistance and obesity. Aberrant expression of circadian genes appears to contribute to the dysregulation of metabolic functions such as insulin secretion, glucose homeostasis and energy expenditure. The potential clinical implications of these findings have been highlighted in animal studies and pilot studies in humans giving rise to the development of circadian interventions strategies including chronotherapy (time-specific therapy), time-restricted feeding, and circadian molecule stabilizers/analogues. Research into these areas will provide insights into the future of circadian medicine in metabolic diseases. In this review, we discuss the physiology of metabolism and the role of circadian timing in regulating these metabolic functions. Also, we review the clinical aspects of circadian physiology and the impact that ongoing and future research may have on the management of metabolic disease.

Cardiovascular effects of incretins - focus on GLP-1 receptor agonists

GLP-1 receptor agonists (GLP-1 RAs) have been used to treat patients with type 2 diabetes since 2005 and have become popular because of the efficacy and durability in relation to glycaemic control in combination with weight loss in most patients. Today in 2022, seven GLP-1 RAs, including oral semaglutide are available for treatment of type 2 diabetes. Since the efficacy in relation to reduction of HbA1c and body weight as well as tolerability and dosing frequency vary between agents, the GLP-1 RAs cannot be considered equal. The short acting lixisenatide showed no cardiovascular benefits, while once daily liraglutide and the weekly agonists, subcutaneous semaglutide, dulaglutide, and efpeglenatide, all lowered the incidence of cardiovascular events. Liraglutide, oral semaglutide and exenatide once weekly also reduced mortality. GLP-1 RAs reduce the progression of diabetic kidney disease. In the 2019 consensus report from EASD/ADA, GLP-1 RAs with demonstrated cardio-renal benefits (liraglutide, semaglutide and dulaglutide) are recommended after metformin to patients with established cardiovascular diseases or multiple cardiovascular risk factors. European Society of Cardiology (ESC) suggests starting with a SGLT-2 inhibitor or a GLP-1 RA in drug naïve patients with type 2 diabetes and atherosclerotic CVD or high CV Risk. However, the results from cardiovascular outcome trials (CVOT) are very heterogeneous suggesting that some GLP-1RA are more suitable to prevent CVD than others. The CVOTs provide a basis upon which individual treatment decisions for patients with T2D and CVD can be made.

Management of type 2 diabetes with the dual GIP/GLP-1 receptor agonist tirzepatide: a systematic review and meta-analysis

AIMS/HYPOTHESIS

Tirzepatide is a novel dual glucose-dependent insulinotropic peptide (GIP) and glucagon-like peptide-1 receptor agonist (GLP-1 RA) currently under review for marketing approval. Individual trials have assessed the clinical profile of tirzepatide vs different comparators. We conducted a systematic review and meta-analysis to assess the efficacy and safety of tirzepatide for type 2 diabetes.

METHODS

We searched PubMed, Embase, Cochrane and ClinicalTrials.gov up until 27 October 2021 for randomised controlled trials with a duration of at least 12 weeks that compared once-weekly tirzepatide 5, 10 or 15 mg with placebo or other glucose-lowering drugs in adults with type 2 diabetes irrespective of their background glucose-lowering treatment. The primary outcome was change in HbA1c from baseline. Secondary efficacy outcomes included change in body weight, proportion of individuals reaching the HbA1c target of <53 mmol/mol (<7.0%), ≤48 mmol/mol (≤6.5%) or <39 mmol/mol (<5.7%), and proportion of individuals with body weight loss of at least 5%, 10% or 15%. Safety outcomes included hypoglycaemia, gastrointestinal adverse events, treatment discontinuation due to adverse events, serious adverse events, and mortality. We used version 2 of the Cochrane risk-of-bias tool for randomised trials to assess risk of bias for the primary outcome.

RESULTS

Seven trials (6609 participants) were included. A dose-dependent superiority in lowering HbA1c was evident with all three tirzepatide doses vs all comparators, with mean differences ranging from -17.71 mmol/mol (-1.62%) to -22.35 mmol/mol (-2.06%) vs placebo, -3.22 mmol/mol (-0.29%) to -10.06 mmol/mol (-0.92%) vs GLP-1 RAs, and -7.66 mmol/mol (-0.70%) to -12.02 mmol/mol (-1.09%) vs basal insulin regimens. Tirzepatide was more efficacious in reducing body weight; reductions vs GLP-1 RAs ranged from 1.68 kg with tirzepatide 5 mg to 7.16 kg with tirzepatide 15 mg. Incidence of hypoglycaemia with tirzepatide was similar vs placebo and lower vs basal insulin. Nausea was more frequent with tirzepatide vs placebo, especially with tirzepatide 15 mg (OR 5.60 [95% CI 3.12, 10.06]), associated with higher incidence of vomiting (OR 5.50 [95% CI 2.40, 12.59]) and diarrhoea (OR 3.31 [95% CI 1.40, 7.85]). Odds of gastrointestinal events were similar between tirzepatide and GLP-1 RAs, except for diarrhoea with tirzepatide 10 mg (OR 1.51 [95% CI 1.07, 2.15]). Tirzepatide 15 mg led to higher discontinuation rate of study medication due to adverse events regardless of comparator, while all tirzepatide doses were safe in terms of serious adverse events and mortality.

CONCLUSIONS/INTERPRETATION

A dose-dependent superiority on glycaemic efficacy and body weight reduction was evident with tirzepatide vs placebo, GLP-1 RAs and basal insulin. Tirzepatide did not increase the odds of hypoglycaemia but was associated with increased incidence of gastrointestinal adverse events. Study limitations include presence of statistical heterogeneity in the meta-analyses for change in HbA1c and body weight, assessment of risk of bias solely for the primary outcome, and generalisation of findings mainly to individuals who are overweight or obese and already on metformin-based background therapy. PROSPERO registration no. CRD42021283449.

Tirzepatide Once Weekly for the Treatment of Obesity

BACKGROUND

Obesity is a chronic disease that results in substantial global morbidity and mortality. The efficacy and safety of tirzepatide, a novel glucose-dependent insulinotropic polypeptide and glucagon-like peptide-1 receptor agonist, in people with obesity are not known.

METHODS

In this phase 3 double-blind, randomized, controlled trial, we assigned 2539 adults with a body-mass index (BMI; the weight in kilograms divided by the square of the height in meters) of 30 or more, or 27 or more and at least one weight-related complication, excluding diabetes, in a 1:1:1:1 ratio to receive once-weekly, subcutaneous tirzepatide (5 mg, 10 mg, or 15 mg) or placebo for 72 weeks, including a 20-week dose-escalation period. Coprimary end points were the percentage change in weight from baseline and a weight reduction of 5% or more. The treatment-regimen estimand assessed effects regardless of treatment discontinuation in the intention-to-treat population.

RESULTS

At baseline, the mean body weight was 104.8 kg, the mean BMI was 38.0, and 94.5% of participants had a BMI of 30 or higher. The mean percentage change in weight at week 72 was -15.0% (95% confidence interval [CI], -15.9 to -14.2) with 5-mg weekly doses of tirzepatide, -19.5% (95% CI, -20.4 to -18.5) with 10-mg doses, and -20.9% (95% CI, -21.8 to -19.9) with 15-mg doses and -3.1% (95% CI, -4.3 to -1.9) with placebo (P<0.001 for all comparisons with placebo). The percentage of participants who had weight reduction of 5% or more was 85% (95% CI, 82 to 89), 89% (95% CI, 86 to 92), and 91% (95% CI, 88 to 94) with 5 mg, 10 mg, and 15 mg of tirzepatide, respectively, and 35% (95% CI, 30 to 39) with placebo; 50% (95% CI, 46 to 54) and 57% (95% CI, 53 to 61) of participants in the 10-mg and 15-mg groups had a reduction in body weight of 20% or more, as compared with 3% (95% CI, 1 to 5) in the placebo group (P<0.001 for all comparisons with placebo). Improvements in all prespecified cardiometabolic measures were observed with tirzepatide. The most common adverse events with tirzepatide were gastrointestinal, and most were mild to moderate in severity, occurring primarily during dose escalation. Adverse events caused treatment discontinuation in 4.3%, 7.1%, 6.2%, and 2.6% of participants receiving 5-mg, 10-mg, and 15-mg tirzepatide doses and placebo, respectively.

CONCLUSIONS

In this 72-week trial in participants with obesity, 5 mg, 10 mg, or 15 mg of tirzepatide once weekly provided substantial and sustained reductions in body weight. (Supported by Eli Lilly; SURMOUNT-1 ClinicalTrials.gov number, NCT04184622.).

Tirzepatide: First Approval

Tirzepatide (Mounjaro™) is a single molecule that combines dual agonism of glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) receptors. Native GIP and GLP-1 are incretin hormones that stimulate insulin secretion and decrease glucagon secretion. GIP also plays a role in nutrient and energy metabolism, while GLP-1 also delays gastric emptying, supresses appetite and improves satiety. Eli Lilly is developing tirzepatide for the treatment of type 2 diabetes mellitus (T2DM), obesity, cardiovascular disorders in T2DM, heart failure, non-alcoholic steatohepatitis, obstructive sleep apnoea and for reducing mortality/morbidity in obesity. In May 2022, tirzepatide received its first approval in the USA to improve glycaemic control in adults with T2DM, as an adjunct to diet and exercise. Tirzepatide is in phase III development for heart failure, obesity and cardiovascular disorders in T2DM, and in phase II development for non-alcoholic steatohepatitis. This article summarizes the milestones in the development of tirzepatide leading to this first approval for T2DM.

Next generation GLP-1/GIP/glucagon triple agonists normalize body weight in obese mice

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.

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Details the design of unimolecular peptide triagonists for GLP-1R/GIPR/GCGR.

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Optimal weight-loss is achieved when receptor potency ratio is weighted toward GCGR vs GLP-1R or GIPR.

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These agonists are protracted for once-weekly human dosing.

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Optimized triagonists normalizes body weight & enhance energy expenditure in mice.

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Efficacy of optimized triagonists is superior to GLP-1R & GLP-1R/GIPR agonists.

Tirzepatide, a New Era of Dual-Targeted Treatment for Diabetes and Obesity: A Mini-Review

The prevalence of obesity and diabetes is an increasing global problem, especially in developed countries, and is referred to as the twin epidemics. As such, advanced treatment approaches are needed. Tirzepatide, known as a ‘twincretin’, is a ‘first-in-class’ and the only dual glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic peptide (GIP) receptor agonist, that can significantly reduce glycemic levels and improve insulin sensitivity, as well as reducing body weight by more than 20% and improving lipid metabolism. This novel anti-diabetic drug is a synthetic peptide analog of the human GIP hormone with a C₂₀ fatty-diacid portion attached which, via acylation technology, can bind to albumin in order to provide a dose of the drug, by means of subcutaneous injection, once a week, which is appropriate to its a half-life of about five days. Tirzepatide, developed by Eli Lilly, was approved, under the brand name Mounjaro, by the United States Food and Drug Administration in May 2022. This started the ‘twincretin’ era of enormously important and appealing dual therapeutic options for diabetes and obesity, as well as advanced management of closely related cardiometabolic settings, which constitute the leading cause of morbidity, disability, and mortality worldwide. Herein, we present the key characteristics of tirzepatide in terms of synthesis, structure, and activity, bearing in mind its advantages and shortcomings. Furthermore, we briefly trace the evolution of this kind of medical agent and discuss the development of clinical studies.

The industrial design, translation, and development strategies for long-acting peptide delivery

INTRODUCTION

Peptides are widely recognized as therapeutic agents in the treatment of a wide range of diseases, such as cancer, diabetes etc. However, their use has been limited by their short half-life, due to significant metabolism by exo- and endo-peptidases as well as their inherent poor physical and chemical stability. Research with the aim of improving their half-life in the body, and thus improving patient compliance (by decreasing the frequency of injections) has gained significant attention.

AREAS COVERED

This review outlines the current landscape and industrial approaches to achieve extended peptide exposure and reduce dosing frequency. Emphasis is placed on identifying challenges in drug product manufacturing and desirable critical quality attributes that are essential for activity and safety, providing insights into chemistry and design aspects impacting peptide release, and summarizing important considerations for CMC developability assessments of sustained release peptide drugs.

EXPERT OPINION

Bring the patient and disease perspective early into development. Substantial advances have been made in the field of sustained delivery of peptides despite their complexity. The article will also highlight considerations for early-stage product design and development, providing an industrial perspective on risk mitigation in developing sustained release peptide drug products.

Tirzepatide induces a thermogenic-like amino acid signature in brown adipose tissue

Objectives

Tirzepatide, a dual GIP and GLP-1 receptor agonist, delivered superior glycemic control and weight loss compared to selective GLP-1 receptor (GLP-1R) agonism in patients with type 2 diabetes (T2D). These results have fueled mechanistic studies focused on understanding how tirzepatide achieves its therapeutic efficacy. Recently, we found that treatment with tirzepatide improves insulin sensitivity in humans with T2D and obese mice in concert with a reduction in circulating levels of branched-chain amino (BCAAs) and keto (BCKAs) acids, metabolites associated with development of systemic insulin resistance (IR) and T2D. Importantly, these systemic effects were found to be coupled to increased expression of BCAA catabolic genes in thermogenic brown adipose tissue (BAT) in mice. These findings led us to hypothesize that tirzepatide may lower circulating BCAAs/BCKAs by promoting their catabolism in BAT.

Methods

To address this question, we utilized a murine model of diet-induced obesity and employed stable-isotope tracer studies in combination with metabolomic analyses in BAT and other tissues.

Results

Treatment with tirzepatide stimulated catabolism of BCAAs/BCKAs in BAT, as demonstrated by increased labeling of BCKA-derived metabolites, and increases in levels of byproducts of BCAA breakdown, including glutamate, alanine, and 3-hydroxyisobutyric acid (3-HIB). Further, chronic administration of tirzepatide increased levels of multiple amino acids in BAT that have previously been shown to be elevated in response to cold exposure. Finally, chronic treatment with tirzepatide led to a substantial increase in several TCA cycle intermediates (α-ketoglutarate, fumarate, and malate) in BAT.

Conclusions

These findings suggest that tirzepatide induces a thermogenic-like amino acid profile in BAT, an effect that may account for reduced systemic levels of BCAAs in obese IR mice.

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Tirzepatide augments the catabolism of BCAA in brown adipose tissue (BAT) of obese mice.

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Tirzepatide promotes BCAA catabolism in BAT, despite its lower potency to activate the mouse GIPR relative to mouse GIP.

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Tirzepatide increases amino acids and TCA cycle intermediates in BAT, as also observed in BAT thermogenesis.

Effects of Hepatic Impairment on the Pharmacokinetics of the Dual GIP and GLP-1 Receptor Agonist Tirzepatide

BACKGROUND AND OBJECTIVE

Tirzepatide, a novel, once-weekly, dual glucose-dependent insulinotropic polypeptide and glucagon-like peptide-1 receptor agonist, is approved in the US as a treatment for type 2 diabetes and is under development for long-term weight management, heart failure with preserved ejection fraction, and nonalcoholic steatohepatitis. This study evaluated the pharmacokinetics and tolerability of tirzepatide in participants with hepatic impairment (with or without type 2 diabetes) versus healthy participants with normal hepatic function.

METHODS

Participants in this parallel, single-dose, open-label study were categorized by hepatic impairment defined by the baseline Child-Pugh (CP) score A (mild impairment; n = 6), B (moderate impairment; n = 6), or C (severe impairment; n = 7) or normal hepatic function (n = 13). All participants received a single subcutaneous 5-mg dose of tirzepatide. Blood samples were collected to determine tirzepatide plasma concentrations to estimate pharmacokinetic parameters. The primary pharmacokinetic parameters of area under the drug concentration-time curve from zero to infinity (AUC0-∞) and maximum observed drug concentration (Cmax) were evaluated using an analysis of covariance. The geometric least-squares means (LSM) and mean ratios for each group, between control and hepatic impairment levels, and the corresponding 90% confidence intervals (CIs) were estimated. The analysis of the time to maximum observed drug concentration was based on a nonparametric method. The relationships between the pharmacokinetic parameters and CP classification parameters (serum albumin level, total bilirubin level, and international normalized ratio) were also assessed. Adverse events were monitored to assess safety and tolerability.

RESULTS

Tirzepatide exposure, based on AUC0-∞ and Cmax, was similar across the control and hepatic impairment groups. Statistical analysis showed no difference in the geometric LSM AUC0-∞ or Cmax between participants in the control group and the hepatic impairment groups, with the 90% CI for the ratios of geometric LSM spanning unity (AUC0-∞ ratio of geometric LSM vs control [90% CI 1.08 [0.879, 1.32], 0.960 [0.790, 1.17], and 0.852 [0.699, 1.04] and Cmax ratio of geometric LSM vs control [90% CI]: 0.916 [0.726, 1.16], 1.00 [0.802, 1.25], and 0.972 [0.784, 1.21] for mild, moderate and severe hepatic impairment groups, respectively). There was no change in median time to Cmax of tirzepatide across all groups (time to Cmax median difference vs control [90% CI]: 0 [- 4.00, 12.00], 0 [- 12.00, 12.00], and 0 [- 11.83, 4.17], respectively). There was no significant relationship between the exposure of tirzepatide and the CP score (p > 0.1 for AUC0-∞, Cmax, and apparent total body clearance). Similarly, there was no clinically relevant relationship between the exposure of tirzepatide and serum albumin level, total bilirubin level, or international normalized ratio. The geometric LSM half-life values were also similar across the control and hepatic impairment groups. No notable differences in safety profiles were observed between participants with hepatic impairment and healthy control participants.

CONCLUSIONS

Tirzepatide pharmacokinetics was similar in participants with varying degrees of hepatic impairment compared with healthy participants. Thus, people with hepatic impairment treated with tirzepatide may not require dose adjustments.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov identifier number NCT03940742.

A comparative transcriptomic analysis of glucagon-like peptide-1 receptor- and glucose-dependent insulinotropic polypeptide receptor-expressing cells in the hypothalamus

OBJECTIVE

The hypothalamus is a key region of the brain implicated in homeostatic regulation, and is an integral centre for the control of feeding behaviour. Glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) are incretin hormones with potent glucoregulatory function through engagement of their respective cognate receptors, GLP-1R and GIPR. Recent evidence indicates that there is a synergistic effect of combining GIP- and GLP-1-based pharmacology on appetite and body weight. The mechanisms underlying the enhanced weight loss exhibited by GIPR/GLP-1R co-agonism are unknown. Gipr and Glp1r are expressed in the hypothalamus in both rodents and humans. To better understand incretin receptor-expressing cell populations, we compared the cell types and expression profiles of Gipr- and Glp1r-expressing hypothalamic cells using single-cell RNA sequencing.

METHODS

Using Glp1r-Cre or Gipr-Cre transgenic mouse lines, fluorescent reporters were introduced into either Glp1r- or Gipr-expressing cells, respectively, upon crossing with a ROSA26-EYFP reporter strain. From the hypothalami of these mice, fluorescent Glp1r^EYFP+ or Gipr^EYFP+ cells were FACS-purified and sequenced using single-cell RNA sequencing. Transcriptomic analysis provided a survey of both non-neuronal and neuronal cells, and comparisons between Glp1r^EYFP+ and Gipr^EYFP + populations were made.

RESULTS

A total of 14,091 Glp1r^EYFP+ and Gipr^EYFP+ cells were isolated, sequenced and taken forward for bioinformatic analysis. Both Glp1r^EYFP+ and Gipr^EYFP+ hypothalamic populations were transcriptomically highly heterogeneous, representing vascular cell types, oligodendrocytes, astrocytes, microglia, and neurons. The majority of Gipr^EYFP+ cells were non-neuronal, whereas the Glp1r^EYFP+ population was evenly split between neuronal and non-neuronal cell types. Both Glp1r^EYFP+ and Gipr^EYFP+ oligodendrocytes express markers for mature, myelin-forming oligodendrocytes. While mural cells are represented in both Glp1r^EYFP+ and Gipr^EYFP+ populations, Glp1r^EYFP+ mural cells are largely smooth muscle cells, while the majority of Gipr^EYFP+ mural cells are pericytes. The co-expression of regional markers indicate that clusters of Glp1r^EYFP+ and Gipr^EYFP+ neurons have been isolated from the arcuate, ventromedial, lateral, tuberal, suprachiasmatic, and premammillary nuclei of the hypothalamus.

CONCLUSIONS

We have provided a detailed comparison of Glp1r and Gipr cells of the hypothalamus with single-cell resolution. This resource will provide mechanistic insight into how engaging Gipr- and Glp1r-expressing cells of the hypothalamus may result in changes in feeding behaviour and energy balance.

GIPR Agonism Inhibits PYY-Induced Nausea-Like Behavior

The induction of nausea and emesis is a major barrier to maximizing the weight loss profile of obesity medications, and therefore, identifying mechanisms that improve tolerability could result in added therapeutic benefit. The development of peptide YY (PYY)-based approaches to treat obesity are no exception, as PYY receptor agonism is often accompanied by nausea and vomiting. Here, we sought to determine whether glucose-dependent insulinotropic polypeptide (GIP) receptor (GIPR) agonism reduces PYY-induced nausea-like behavior in mice. We found that central and peripheral administration of a GIPR agonist reduced conditioned taste avoidance (CTA) without affecting hypophagia mediated by a PYY analog. The receptors for GIP and PYY (Gipr and Npy2r) were found to be expressed by the same neurons in the area postrema (AP), a brainstem nucleus involved in detecting aversive stimuli. Peripheral administration of a GIPR agonist induced neuronal activation (cFos) in the AP. Further, whole-brain cFos analyses indicated that PYY-induced CTA was associated with augmented neuronal activity in the parabrachial nucleus (PBN), a brainstem nucleus that relays aversive/emetic signals to brain regions that control feeding behavior. Importantly, GIPR agonism reduced PYY-mediated neuronal activity in the PBN, providing a potential mechanistic explanation for how GIPR agonist treatment reduces PYY-induced nausea-like behavior. Together, the results of our study indicate a novel mechanism by which GIP-based therapeutics may have benefit in improving the tolerability of weight loss agents.

Type 2 Diabetes Remission with Significant Weight Loss: Definition and Evidence-Based Interventions

Type 2 diabetes (T2D) has long been regarded as an incurable and chronic disease according to conventional management methods. Clinical and pathophysiological studies on the natural course of T2D have shown that blood glucose control worsens with an increase in the number of required anti-hyperglycemic agents, as β-cell function progressively declines over time. However, recent studies have shown remission of T2D after metabolic surgery, intensive lifestyle modification, or medications, raising the possibility that β-cell function may be preserved or the decline in β-cell function may even be reversible. The World Health Organization as well as the American Diabetes Association and the European Association for the Study of Diabetes recognize remission as an appropriate management aim. In the light of the state of evidence for T2D reversal, physicians need to be educated on treatment options to achieve T2D remission so that they can actively play a part in counseling patients who may wish to explore these approaches to their disease. This review will introduce each of these approaches, summarizing their beneficial effects, supporting evidence, degree of sustainability, and challenges to be addressed in the future.

Designing a Dual GLP-1R/GIPR Agonist from Tirzepatide: Comparing Residues Between Tirzepatide, GLP-1, and GIP

Improving type 2 diabetes using incretin analogues is becoming increasingly plausible. Currently, tirzepatide is the most promising listed incretin analogue. Here, I briefly explain the evolution of drugs of this kind, analyze the residue discrepancies between tirzepatide and endogenous incretins, summarize some existing strategies for prolonging half-life, and present suggestions for future research, mainly involving biased functions. This review aims to present some useful information for designing a dual glucagon like peptide-1 receptor/glucose-dependent insulinotropic polypeptide receptor agonist.

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Efficacy of once-weekly tirzepatide versus once-daily insulin degludec on glycaemic control measured by continuous glucose monitoring in adults with type 2 diabetes (SURPASS-3 CGM): a substudy of the randomised, open-label, parallel-group, phase 3 SURPASS-3 trial

BACKGROUND

Tirzepatide is a novel dual glucose-dependent insulinotropic polypeptide (GIP) and GLP-1 receptor agonist under development for the treatment of type 2 diabetes. In this study, we used continuous glucose monitoring (CGM) to compare the 24 h glucose profile for participants given tirzepatide compared with those given insulin degludec.

METHODS

This substudy of the open-label, parallel-group, phase 3 SURPASS-3 trial, was done at 45 sites across six countries (Hungary, Poland, Romania, Spain, Ukraine, and the USA). Eligible participants in the main study were adults with type 2 diabetes, a baseline HbA_1c of 7·0-10·5% (53-91 mmol/mol), and a BMI of 25 kg/m² or more, who were insulin-naive, and treated with metformin alone or in combination with a SGLT2 inhibitor for at least 3 months before screening. Participants in the main study were randomly assigned (1:1:1:1) to receive once-weekly subcutaneous injection of tirzepatide 5 mg, 10 mg, or 15 mg, or once-daily subcutaneous injection of titrated insulin degludec (100 U/mL), using an interactive web-response system. Participants were stratified by country, HbA_1c concentration, and concomitant oral antihyperglycaemic medication. A subset of these patients with a normal wake-sleep cycle were enrolled into this substudy, and interstitial glucose values were collected by CGM for approximately 7 days at baseline, 24 weeks, and 52 weeks. The primary outcome was to compare pooled participants assigned to 10 mg and 15 mg tirzepatide versus insulin degludec for the proportion of time that CGM values were in the tight target range (71-140 mg/dL) at 52 weeks, assessed in all randomly assigned participants who received at least one dose of study drug and had an evaluable CGM session at either baseline or after baseline. The secondary outcomes were to compare tirzepatide (5 mg, 10 mg, and 15 mg) versus insulin degludec for the proportion and duration of time in tight target range at 24 and 52 weeks. This was a substudy of the trial registered with ClinicalTrials.gov, NCT03882970, and is complete.

FINDINGS

From April 1 to Nov 27, 2019, 313 participants were screened for eligibility, 243 of whom were enrolled in CGM substudy (tirzepatide 5 mg, n=64; tirzepatide 10 mg, n=51; tirzepatide 15 mg, n=73; and insulin degludec, n=55). Patients given once-weekly tirzepatide (pooled 10 mg and 15 mg groups) had a greater proportion of time in tight target range compared with patients given insulin degludec (estimated treatment difference 25% [95% CI 16-33]; p<0·0001). Participants assigned to tirzepatide spent significantly more time in tight target range at 52 weeks compared with those assigned to insulin degludec (5 mg 12% [1-22], p=0·031; 10 mg 24% [13-35], p<0·0001; and 15 mg 25% [14-35], p<0·0001). Participants assigned to tirzepatide 10 mg and 15 mg, but not to tirzepatide 5 mg, spent significantly more time in tight target range at 24 weeks compared with insulin degludec (10 mg 19% [8-30], p=0·0008; 15 mg 21% [11-31], p<0·0001).

INTERPRETATION

Once-weekly treatment with tirzepatide showed superior glycaemic control measured using CGM compared with insulin degludec in participants with type 2 diabetes on metformin, with or without a SGLT2 inhibitor. These new data provide additional evidence to the effect of tirzepatide and potential for achieving glycaemic targets without increase of hypoglycaemic risk compared with a basal insulin.

FUNDING

Eli Lilly and Company.

Effect of tirzepatide versus insulin degludec on liver fat content and abdominal adipose tissue in people with type 2 diabetes (SURPASS-3 MRI): a substudy of the randomised, open-label, parallel-group, phase 3 SURPASS-3 trial

BACKGROUND

Tirzepatide is a novel dual glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 receptor agonist under development for the treatment of type 2 diabetes. The aim of this substudy was to characterise the changes in liver fat content (LFC), volume of visceral adipose tissue (VAT), and abdominal subcutaneous adipose tissue (ASAT) in response to tirzepatide or insulin degludec in a subpopulation of the SURPASS-3 study.

METHODS

This substudy of the randomised, open-label, parallel-group, phase 3 SURPASS-3 trial was done at 45 medical research centres and hospitals across eight countries (Argentina, Austria, Greece, Hungary, Italy, Romania, Spain, and the USA). Eligible participants were adults with type 2 diabetes, a baseline HbA_1c 7·0-10·5% (53-91 mmol/mol), a BMI of at least 25 kg/m², stable weight, were insulin-naive, and on treatment with metformin alone or in combination with a SGLT2 inhibitor for at least 3 months before screening. In addition to the main study inclusion criteria, substudy participants had a fatty liver index of at least 60. Participants had an MRI scan and were randomised (1:1:1:1) in the main study to subcutaneous injection once per week of tirzepatide 5 mg, 10 mg, or 15 mg, or subcutaneous injection once per day of titrated insulin degludec, using an interactive web-response system, and were stratified by country, HbA_1c, and concomitant oral anti-hyperglycaemic medication. The primary efficacy endpoint was the change from baseline in LFC (as measured by MRI-proton density fat fraction [MRI-PDFF]) at week 52 using pooled data from the tirzepatide 10 mg and 15 mg groups versus insulin degludec. Analyses were assessed in the enrolled MRI population, which consisted of participants in the modified intention-to-treat population of the main study who also had a valid MRI at either baseline or after baseline. This is a substudy of the trial registered with ClinicalTrials.gov, number NCT03882970, and is complete.

FINDINGS

From April 1, 2019, to Nov 15, 2019, 502 participants were assessed for eligibility to participate in this substudy, 296 (59%) of whom were included in the enrolled MRI population and randomly assigned to treatment (tirzepatide 5 mg, n=71; tirzepatide 10 mg, n=79; tirzepatide 15 mg, n=72; and insulin degludec, n=74). Baseline demographics and clinical characteristics were similar across all treatment groups. From an overall mean baseline LFC of 15·71% (SD 8·93), the absolute reduction in LFC at week 52 was significantly greater for the pooled tirzepatide 10 mg and 15 mg groups (-8·09%, SE 0·57) versus the insulin degludec group (-3·38%, 0·83). The estimated treatment difference versus insulin degludec was -4·71% (95% CI -6·72 to -2·70; p<0·0001). The reduction in LFC was significantly correlated (p≤0·0006) with baseline LFC (ρ=-0·71), reductions in VAT (ρ=0·29), reductions in ASAT (ρ=0·33), and reductions in body weight (ρ=0·34) in the tirzepatide groups.

INTERPRETATION

Tirzepatide showed a significant reduction in LFC and VAT and ASAT volumes compared with insulin degludec in this subpopulation of patients with type 2 diabetes in the SURPASS-3 study. These data provide additional evidence on the metabolic effects of this novel dual GIP and GLP-1 receptor agonist.

FUNDING

Eli Lilly and Company.

Effects of subcutaneous tirzepatide versus placebo or semaglutide on pancreatic islet function and insulin sensitivity in adults with type 2 diabetes: a multicentre, randomised, double-blind, parallel-arm, phase 1 clinical trial

BACKGROUND

Tirzepatide, a dual glucose-dependent insulinotropic polypeptide (GIP)/GLP-1 receptor agonist, shows a remarkable ability to lower blood glucose, enabling many patients with long-standing type 2 diabetes to achieve normoglycaemia. We aimed to understand the physiological mechanisms underlying the action of tirzepatide in type 2 diabetes.

METHODS

This multicentre, randomised, double-blind, parallel-arm, phase 1 study was done at two centres in Germany. Eligible patients were aged 20-74 years, had type 2 diabetes for at least 6 months, and were being treated with lifestyle advice and stable doses of metformin, with or without one additional stable dose of another oral antihyperglycaemic medicine, 3 months before study entry. Via a randomisation table, patients were randomly assigned (3:3:2) to subcutaneously receive either tirzepatide 15 mg, semaglutide 1 mg, or placebo once per week. Endpoint measurements were done at baseline and the last week of therapy (week 28). The primary endpoint was the effect of tirzepatide versus placebo on the change in clamp disposition index (combining measures of insulin secretion and sensitivity) from baseline to week 28 of treatment and was analysed in the pharmacodynamic analysis set, which comprised all randomly assigned participants who received at least one dose of a study drug and had evaluable pharmacodynamic data. Safety was analysed in the safety population, which comprised all randomly assigned participants who received at least one dose of a study drug. Secondary endpoints included the effect of tirzepatide versus semaglutide on the change in clamp disposition index from baseline to week 28 of treatment, glucose control, total insulin secretion rate, M value (insulin sensitivity), and fasting and postprandial glucagon concentrations. Exploratory endpoints included the change in fasting and postprandial insulin concentrations. This study is registered with ClinicalTrials.gov, NCT03951753, and is complete.

FINDINGS

Between June 28, 2019, and April 8, 2021, we screened 184 individuals and enrolled 117 participants, all of whom were included in the safety population (45 in the tirzepatide 15 mg group, 44 in the semaglutide 1 mg group, and 28 in the placebo group). Because of discontinuations and exclusions due to missing or unevaluable data, 39 patients in each treatment group and 24 patients in the placebo group comprised the pharmacodynamic analysis set. With tirzepatide, the clamp disposition index increased from a least squares mean of 0·3 pmol m^-2 L min^-2 kg^-1 (SE 0·03) at baseline by 1·9 pmol m^-2 L min^-2 kg^-1 (0·16) to total 2·3 pmol m^-2 L min^-2 kg^-1 (SE 0·16) at week 28 and, with placebo, the clamp disposition index did not change much from baseline (least squares mean at baseline 0·4 pmol m^-2 L min^-2 kg^-1 [SE 0·04]; change from baseline 0·0 pmol m^-2 L min^-2 kg^-1 [0·03]; least squares mean at week 28 0·3 [SE 0·03]; estimated treatment difference [ETD] tirzepatide vs placebo 1·92 [95% CI 1·59-2·24]; p<0·0001). The improvement with tirzepatide in clamp disposition index was significantly greater than with semaglutide (ETD 0·84 pmol m^-2 L min^-2 kg^-1 [95% CI 0·46-1·21]). This result reflected significant improvements in total insulin secretion rate (ETD 102·09 pmol min^-1 m^-2 [51·84-152·33]) and insulin sensitivity (ETD 1·52 mg min^-1 kg^-1 [0·53-2·52]) for tirzepatide versus semaglutide. On meal tolerance testing, tirzepatide significantly reduced glucose excursions (lower insulin and glucagon concentrations) compared with placebo, with effects on these variables being greater than with semaglutide. The safety profiles of tirzepatide and semaglutide were similar, with gastrointestinal adverse events being the most common (11 [24%], 13 [30%], and seven [25%] with nausea; nine [20%], 13 [30%], and six [21%] with diarrhoea; and three [7%], five [11%], and one [4%] with vomiting, for tirzepatide, semaglutide, and placebo, respectively). There were no deaths.

INTERPRETATION

The glycaemic efficacy of GIP/GLP-1 receptor agonist tirzepatide in type 2 diabetes results from concurrent improvements in key components of diabetes pathophysiology, namely β-cell function, insulin sensitivity, and glucagon secretion. These effects were large and help to explain the remarkable glucose-lowering ability of tirzepatide seen in phase 3 studies.

FUNDING

Eli Lilly.

Glucose-Dependent Insulinotropic Polypeptide-A Postprandial Hormone with Unharnessed Metabolic Potential

Glucose-dependent insulinotropic polypeptide (GIP) is released from the upper small intestine in response to food intake and contributes to the postprandial control of nutrient disposition, including of sugars and fats. Long neglected as a potential therapeutic target, the GIPR axis has received increasing interest recently, with the emerging data demonstrating the metabolically favorable outcomes of adding GIPR agonism to GLP-1 receptor agonists in people with type 2 diabetes and obesity. This review examines the physiology of the GIP axis, from the mechanisms underlying GIP secretion from the intestine to its action on target tissues and therapeutic development. Expected final online publication date for the Annual Review of Nutrition, Volume 42 is August 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Design of Potent and Proteolytically Stable Biaryl-Stapled GLP-1R/GIPR Peptide Dual Agonists

Recent clinical trials have revealed that the chimeric peptide hormones simultaneously activating glucagon-like peptide-1 receptor (GLP-1R) and glucose-dependent insulinotropic polypeptide receptor (GIPR) demonstrate superior efficacy in glycemic control and body weight reduction, better than those activating the GLP-1R alone. However, the linear peptide-based GLP-1R/GIPR dual agonists are susceptible to proteolytic cleavage by common digestive enzymes present in the gastrointestinal tract and thus not suitable for oral administration. Here, we report the design and synthesis of biaryl-stapled peptides, with and without fatty diacid attachment, that showed potent GLP-1R/GIPR dual agonist activities. Compared to a linear peptide dual agonist and semaglutide, the biaryl-stapled peptides displayed drastically improved proteolytic stability against the common digestive enzymes. Furthermore, two stapled peptides showed excellent efficacy in an oral glucose tolerance test in mice, owing to their potent receptor activity in vitro and good pharmacokinetics exposure upon subcutaneous injection. By exploring a more comprehensive set of biaryl staplers, we expect that this stapling method could facilitate the design of the stapled peptide-based dual agonists suitable for oral administration.

Novel Noninvasive Approaches to the Treatment of Obesity: From Pharmacotherapy to Gene Therapy

Recent insights into the pathophysiologic underlying mechanisms of obesity have led to the discovery of several promising drug targets and novel therapeutic strategies to address the global obesity epidemic and its comorbidities. Current pharmacologic options for obesity management are largely limited in number and of modest efficacy/safety profile. Therefore, the need for safe and more efficacious new agents is urgent. Drugs that are currently under investigation modulate targets across a broad range of systems and tissues, including the central nervous system, gastrointestinal hormones, adipose tissue, kidney, liver, and skeletal muscle. Beyond pharmacotherapeutics, other potential antiobesity strategies are being explored, including novel drug delivery systems, vaccines, modulation of the gut microbiome, and gene therapy. The present review summarizes the pathophysiology of energy homeostasis and highlights pathways being explored in the effort to develop novel antiobesity medications and interventions but does not cover devices and bariatric methods. Emerging pharmacologic agents and alternative approaches targeting these pathways and relevant research in both animals and humans are presented in detail. Special emphasis is given to treatment options at the end of the development pipeline and closer to the clinic (ie, compounds that have a higher chance to be added to our therapeutic armamentarium in the near future). Ultimately, advancements in our understanding of the pathophysiology and interindividual variation of obesity may lead to multimodal and personalized approaches to obesity treatment that will result in safe, effective, and sustainable weight loss until the root causes of the problem are identified and addressed.

A Novel Dual Incretin Agent, Tirzepatide (LY3298176), for the treatment of Type 2 Diabetes Mellitus and Cardiometabolic Health

ABSTRACT

The incretin hormone system is the target of multiple type 2 diabetes mellitus (T2DM) treatments because defects in this system play major roles in the pathogenesis of diabetes. Currently, the glucagon-like peptide (GLP-1) receptor agonists are recommended for patients with atherosclerotic cardiovascular disease (ASCVD) and those at high risk for ASCVD. In addition to the favorable cardiovascular effects, GLP-1 RAs also provide robust lowering of hemoglobin A1c and weight. While these factors make GLP-1 RAs attractive options for T2DM, the currently available agents have no effect on glucose-dependent insulinotropic polypeptide (GIP). Patients with T2DM are known to have GIP defect which is significant due to its profound insulinotropic effects. Tirzepatide is a novel incretin agent currently under review by the Food and Drug Administration for the treatment of type 2 diabetes. This first-in-class agent serves as a co-agonist for both the GLP-1 and GIP receptors. In this review, we report on the pharmacologic mechanism of GLP-1, GIP and co-agonist effects on the cardiometabolic system. Additionally, we review the glycemic lowering, weight-loss effects, and other cardiometabolic outcomes of tirzepatide based on phase 2 and 3 data. The safety profile of tirzepatide is consistent across all phase 3 trials. The most common adverse effects are gastrointestinal symptoms, but they generally have a low risk for discontinuation. Overall, preliminary data suggests tirzepatide is an efficacious and safe agent for the treatment of T2DM.

GIPR Is Predominantly Localized to Nonadipocyte Cell Types Within White Adipose Tissue

The incretin hormone glucose-dependent insulinotropic polypeptide (GIP) augments glucose-dependent insulin secretion through its receptor expressed on islet β-cells. GIP also acts on adipose tissue; yet paradoxically, both enhanced and reduced GIP receptor (GIPR) signaling reduce adipose tissue mass and attenuate weight gain in response to nutrient excess. Moreover, the precise cellular localization of GIPR expression within white adipose tissue (WAT) remains uncertain. We used mouse genetics to target Gipr expression within adipocytes. Surprisingly, targeting Cre expression to adipocytes using the adiponectin (Adipoq) promoter did not produce meaningful reduction of WAT Gipr expression in Adipoq-Cre:Giprflx/flx mice. In contrast, adenoviral expression of Cre under the control of the cytomegalovirus promoter, or transgenic expression of Cre using nonadipocyte-selective promoters (Ap2/Fabp4 and Ubc) markedly attenuated WAT Gipr expression. Analysis of single-nucleus RNA-sequencing, adipose tissue data sets localized Gipr/GIPR expression predominantly to pericytes and mesothelial cells rather than to adipocytes. Together, these observations reveal that adipocytes are not the major GIPR+ cell type within WAT-findings with mechanistic implications for understanding how GIP and GIP-based co-agonists control adipose tissue biology.

GLP-1 and GIP receptor signaling in beta cells - A review of receptor interactions and co-stimulation

Glucagon-like peptide 1 receptor (GLP-1R) and glucose-dependent insulinotropic polypeptide receptor (GIPR) are two class B1 G protein-coupled receptors, which are stimulated by the gastrointestinal hormones GLP-1 and GIP, respectively. In the pancreatic beta cells, activation of both receptors lead to increased cyclic adenosine monophosphate (cAMP) and glucose-dependent insulin secretion. Marketed GLP-1R agonists such as dulaglutide, liraglutide, exenatide and semaglutide constitute an expanding drug class with beneficial effects for persons suffering from type 2 diabetes and/or obesity. In recent years another drug class, the GLP-1R-GIPR co-agonists, has emerged. Especially the peptide-based, co-agonist tirzepatide is a promising candidate for a better treatment of type 2 diabetes by improving glycemic control and weight reduction. The mechanism of action for tirzepatide include biased signaling of the GLP-1R as well as potent GIPR signaling. Since the implications of co-targeting these closely related receptors concomitantly are challenging to study in vivo, the pharmacodynamic mechanisms and downstream signaling pathways of the GLP-1R-GIPR co-agonists in general, are not fully elucidated. In this review, we present the individual signaling pathways for GLP-1R and GIPR in the pancreatic beta cell with a focus on the shared signaling pathways of the two receptors and interpret the implications of GLP-1R-GIPR co-activation in the light of recent co-activating therapeutic compounds.

Managing weight and glycaemic targets in people with type 2 diabetes—How far have we come?

Introduction

As the vast majority of people with type 2 diabetes (T2D) are also overweight or obese, healthcare professionals (HCP) are faced with the task of addressing both weight management and glucose control. In this narrative review, we aim to identify the challenges of reaching and maintaining body weight targets in people with T2D and highlight current and future treatment interventions.

Methods

A search of the PubMed database was conducted using the search terms “diabetes” and “weight loss.”

Results

According to emerging evidence, treating obesity may be antecedent to the development and progression of T2D. While clinical benefits typically set in upon achieving a weight loss of 3–5%, these benefits are progressive leading to further health improvements, and weight loss of >15% can have a disease‐modifying effect in people with T2D, an outcome that up to recently could not be achieved with any blood glucose‐lowering pharmacotherapy. However, advanced treatment options with weight‐loss effects currently in development including the dual GIP/GLP‐1 receptor agonists may enable simultaneous achievement of individual glycemic and weight goals.

Conclusion

Despite considerable therapeutic progress, there is still a large unmet medical need in patients with T2D who miss their individualized glycemic and weight‐loss targets. Nonetheless, it is to be expected that development of future therapies and their use will favourably change the scenario of weight and glucose control in T2D.

Efficacy and safety of high-dose glucagon-like peptide-1, glucagon-like peptide-1/glucose-dependent insulinotropic peptide, and glucagon-like peptide-1/glucagon receptor agonists in type 2 diabetes

Glucagon-like peptide-1 receptor agonists (GLP-1 RAs) have become agents of choice for people with type 2 diabetes (T2D) with established cardiovascular disease or in high-risk individuals. With currently available GLP-1 RAs, 51%-79% of subjects achieve an HbA1c target of less than 7.0% and 4%-27% lose 10% of body weight, illustrating the need for more potent agents. Three databases (PubMed, Cochrane, Web of Science) were searched using the MESH terms 'glucagon-like peptide-1 receptor agonist', 'glucagon receptor agonist', 'glucose-dependent insulinotropic peptide', 'dual or co-agonist', and 'tirzepatide'. Quality of papers was scored using PRISMA guidelines. Risk of bias was evaluated using the Cochrane assessment tool. An HbA1c target of less than 7.0% was attained by up to 80% with high-dose GLP-1 RAs and up to 97% with tirzepatide, with even up to 62% of people with T2D reaching an HbA1c of less than 5.7%. A body weight loss of 10% or greater was obtained by up to 50% and up to 69% with high-dose GLP-1 RAs or tirzepatide, respectively. The glucose- and weight-lowering effects of the GLP-1/glucagon RA cotadutide equal those of liraglutide 1.8 mg. Gastrointestinal side effects of high-dose GLP-1 RAs and co-agonists occurred in 30%-70% of patients, mostly arising within the first 2 weeks of the first dose, being mild or moderate in severity, and transient. The development of high-dose GLP-1 RAs and the dual GLP-1/glucose-dependent insulinotropic peptide RA tirzepatide resulted in increasing numbers of people reaching HbA1c and body weight targets, with up to 62% attaining normoglycaemia with 15-mg tirzepatide. Whether this will also translate to better cardiovascular outcomes and affect treatment guidelines remains to be studied.

The Upcoming Weekly Tides (Semaglutide vs. Tirzepatide) against Obesity: STEP or SURPASS?

The rapidly increasing prevalence of obesity and obesity-associated morbidity is causing an ever-increasing global burden. Beyond lifestyle modifications, pharmacological approaches to losing body weight to achieve a decrease in cardiometabolic complications are in the spotlight. Pre-existing anti-obesity medications (AOMs) approved for long-term prescription use showed a weight reduction of around 5% more than placebo. In contrast to the modest efficacy of pre-existing AOMs, two newly developed, weekly-administered injectable drugs, semaglutide and tirzepatide, exhibited outstanding weight-loss effects in a series of multinational randomized phase III trials. Considering that these two peptides are the most promising candidates for the upcoming battle in the anti-obesity market, comparison of their efficacy and safety is essential. This review summarizes the body weight reduction efficacy, glycemic control, and safety of semaglutide up to a 2.4-mg dose and tirzepatide up to a 15-mg dose, focusing on the Semaglutide Treatment Effect in People with Obesity (STEP) 2, SURPASS-1, and SURPASS-2 trials, the subjects of which were all patients with type 2 diabetes mellitus.

Structural determinants of dual incretin receptor agonism by tirzepatide

Tirzepatide 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.

Tirzepatide (LY3298176) is a fatty-acid-modified, dual incretin receptor agonist that exhibits pharmacology similar to native GIP at the glucose-dependent insulinotropic polypeptide receptor (GIPR) but shows bias toward cyclic adenosine monophosphate signaling at the glucagon-like peptide-1 receptor (GLP-1R). In addition to GIPR signaling, the pathway bias at the GLP-1R may contribute to the efficacy of tirzepatide at improving glucose control and body weight regulation in type 2 diabetes mellitus. To investigate the structural basis for the differential signaling of tirzepatide, mechanistic pharmacology studies were allied with cryogenic electron microscopy. Here, we report high-resolution structures of tirzepatide in complex with the GIPR and GLP-1R. Similar to the native ligands, tirzepatide adopts an α-helical conformation with the N terminus reaching deep within the transmembrane core of both receptors. Analyses of the N-terminal tyrosine (Tyr1^Tzp) of tirzepatide revealed a weak interaction with the GLP-1R. Molecular dynamics simulations indicated a greater propensity of intermittent hydrogen bonding between the lipid moiety of tirzepatide and the GIPR versus the GLP-1R, consistent with a more compact tirzepatide–GIPR complex. Informed by these analyses, tirzepatide was deconstructed, revealing a peptide structure–activity relationship that is influenced by acylation-dependent signal transduction. For the GIPR, Tyr1^Tzp and other residues making strong interactions within the receptor core allow tirzepatide to tolerate fatty acid modification, yielding an affinity equaling that of GIP. Conversely, high-affinity binding with the extracellular domain of the GLP-1R, coupled with decreased stability from the Tyr1^Tzp and the lipid moiety, foster biased signaling and reduced receptor desensitization. Together, these studies inform the structural determinants underlying the function of tirzepatide.

Lipidomic Analysis Reveals the Protection Mechanism of GLP-1 Analogue Dulaglutide on High-Fat Diet-Induced Chronic Kidney Disease in Mice

Many clinical studies have suggested that glucagon-like peptide-1 receptor agonists (GLP-1RAs) have renoprotective properties by ameliorating albuminuria and increasing glomerular filtration rate in patients with type 2 diabetes mellitus (T2DM) and chronic kidney disease (CKD) by lowering ectopic lipid accumulation in the kidney. However, the mechanism of GLP-1RAs was hitherto unknown. Here, we conducted an unbiased lipidomic analysis using ultra-high-performance liquid chromatography/electrospray ionization-quadrupole time-of-flight mass spectrometry (UHPLC/ESI-Q-TOF-MS) and matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) to reveal the changes of lipid composition and distribution in the kidneys of high-fat diet-fed mice after treatment with a long-acting GLP-1RA dulaglutide for 4 weeks. Treatment of dulaglutide dramatically improved hyperglycemia and albuminuria, but there was no substantial improvement in dyslipidemia and ectopic lipid accumulation in the kidney as compared with controls. Intriguingly, treatment of dulaglutide increases the level of an essential phospholipid constituent of inner mitochondrial membrane cardiolipin at the cortex region of the kidneys by inducing the expression of key cardiolipin biosynthesis enzymes. Previous studies demonstrated that lowered renal cardiolipin level impairs kidney function via mitochondrial damage. Our untargeted lipidomic analysis presents evidence for a new mechanism of how GLP-1RAs stimulate mitochondrial bioenergetics via increasing cardiolipin level and provides new insights into the therapeutic potential of GLP-1RAs in mitochondrial-related diseases.

An integrated platform approach enables discovery of potent, selective and ligand-competitive cyclic peptides targeting the GIP receptor

In any drug discovery effort, the identification of hits for further optimisation is of crucial importance. For peptide therapeutics, display technologies such as mRNA display have emerged as powerful methodologies to identify these desired de novo hit ligands against targets of interest. The diverse peptide libraries are genetically encoded in these technologies, allowing for next-generation sequencing to be used to efficiently identify the binding ligands. Despite the vast datasets that can be generated, current downstream methodologies, however, are limited by low throughput validation processes, including hit prioritisation, peptide synthesis, biochemical and biophysical assays. In this work we report a highly efficient strategy that combines bioinformatic analysis with state-of-the-art high throughput peptide synthesis to identify nanomolar cyclic peptide (CP) ligands of the human glucose-dependent insulinotropic peptide receptor (hGIP-R). Furthermore, our workflow is able to discriminate between functional and remote binding non-functional ligands. Efficient structure-activity relationship analysis (SAR) combined with advanced in silico structural studies allow deduction of a thorough and holistic binding model which informs further chemical optimisation, including efficient half-life extension. We report the identification and design of the first de novo, GIP-competitive, incretin receptor family-selective CPs, which exhibit an in vivo half-life up to 10.7 h in rats. The workflow should be generally applicable to any selection target, improving and accelerating hit identification, validation, characterisation, and prioritisation for therapeutic development.

Implications of ligand-receptor binding kinetics on GLP-1R signalling

G protein-coupled receptors (GPCRs) are the largest class of membrane proteins and in recent years there has been a growing appreciation of the importance in understanding temporal aspects of GPCR behaviour, including the kinetics of ligand binding and downstream receptor mediated signalling. Class B1 GPCRs are activated by peptide agonists and are validated therapeutic targets for numerous diseases. However, the kinetics of ligand binding and how this is linked to downstream activation of signalling cascades is not routinely assessed in development of peptide agonists for this receptor class. The glucagon-like peptide-1 receptor (GLP-1R) is a prototypical class B1 GPCR and a validated target for treatment of global health burdens, including type 2 diabetes and obesity. In this study we examined the kinetics of different steps in GLP-1R activation and subsequent cAMP production mediated by a series of GLP-1R peptide agonists, including the ligand-receptor interaction, ligand-receptor-mediated G protein engagement and conformational change and cAMP production. Our results revealed GLP-1R peptide agonist dissociation kinetics (K_off), but not association kinetics (K_on), were positively correlated with the onset of receptor-G protein coupling/conformational change, onset of cAMP production and duration of cAMP signalling. Thus, this study advances the understanding of molecular events that couple GLP-1R ligand binding to intracellular signaling, with the findings likely to have implications for mechanistic understanding of agonist action at other related class B1 GPCRs.

Gut peptide regulation of food intake - evidence for the modulation of hedonic feeding

The number of people living with obesity has tripled worldwide since 1975 with serious implications for public health, as obesity is linked to a significantly higher chance of early death from associated comorbidities (metabolic syndrome, type 2 diabetes, cardiovascular disease and cancer). As obesity is a consequence of food intake exceeding the demands of energy expenditure, efforts are being made to better understand the homeostatic and hedonic mechanisms governing food intake. Gastrointestinal peptides are secreted from enteroendocrine cells in response to nutrient and energy intake, and modulate food intake either via afferent nerves, including the vagus nerve, or directly within the central nervous system, predominantly gaining access at circumventricular organs. Enteroendocrine hormones modulate homeostatic control centres at hypothalamic nuclei and the dorso-vagal complex. Additional roles of these peptides in modulating hedonic food intake and/or preference via the neural systems of reward are starting to be elucidated, with both peripheral and central peptide sources potentially contributing to central receptor activation. Pharmacological interventions and gastric bypass surgery for the treatment of type 2 diabetes and obesity elevate enteroendocrine hormone levels and also alter food preference. Hence, understanding of the hedonic mechanisms mediated by gut peptide action could advance development of potential therapeutic strategies for the treatment of obesity and its comorbidities.

Structural insights into multiplexed pharmacological actions of tirzepatide and peptide 20 at the GIP, GLP-1 or glucagon receptors

Glucose homeostasis, regulated by glucose-dependent insulinotropic polypeptide (GIP), glucagon-like peptide-1 (GLP-1) and glucagon (GCG) is critical to human health. Several multi-targeting agonists at GIPR, GLP-1R or GCGR, developed to maximize metabolic benefits with reduced side-effects, are in clinical trials to treat type 2 diabetes and obesity. To elucidate the molecular mechanisms by which tirzepatide, a GIPR/GLP-1R dual agonist, and peptide 20, a GIPR/GLP-1R/GCGR triagonist, manifest their multiplexed pharmacological actions over monoagonists such as semaglutide, we determine cryo-electron microscopy structures of tirzepatide-bound GIPR and GLP-1R as well as peptide 20-bound GIPR, GLP-1R and GCGR. The structures reveal both common and unique features for the dual and triple agonism by illustrating key interactions of clinical relevance at the near-atomic level. Retention of glucagon function is required to achieve such an advantage over GLP-1 monotherapy. Our findings provide valuable insights into the structural basis of functional versatility of tirzepatide and peptide 20.

Multi-targeting agonists at GIPR, GLP-1R or GCGR are pursued vigorously. Here, the authors report cryo-EM structures of tirzepatide-bound GIPR and GLP-1R, peptide 20-bound GIPR, GLP-1R and GCGR, revealing the molecular basis of their multiplexed pharmacological actions.

Tirzepatide cardiovascular event risk assessment: a pre-specified meta-analysis

Tirzepatide is a novel, once weekly, dual GIP/GLP-1 receptor agonist and is under development for the treatment of type 2 diabetes (T2D) and obesity. Its association with cardiovascular outcomes requires evaluation. This pre-specified cardiovascular meta-analysis included all seven randomized controlled trials with a duration of at least 26 weeks from the tirzepatide T2D clinical development program, SURPASS. The pre-specified primary objective of this meta-analysis was the comparison of the time to first occurrence of confirmed four-component major adverse cardiovascular events (MACE-4; cardiovascular death, myocardial infarction, stroke and hospitalized unstable angina) between pooled tirzepatide groups and control groups. A stratified Cox proportional hazards model, with treatment as a fixed effect and trial-level cardiovascular risk as the stratification factor, was used for the estimation of hazard ratios (HRs) and confidence intervals (CIs) comparing tirzepatide to control. Data from 4,887 participants treated with tirzepatide and 2,328 control participants were analyzed. Overall, 142 participants, 109 from the trial with high cardiovascular risk and 33 from the six trials with lower cardiovascular risk, had at least one MACE-4 event. The HRs comparing tirzepatide versus controls were 0.80 (95% CI, 0.57-1.11) for MACE-4; 0.90 (95% CI, 0.50-1.61) for cardiovascular death; and 0.80 (95% CI, 0.51-1.25) for all-cause death. No evidence of effect modifications was observed for any subgroups, although the evidence was stronger for participants with high cardiovascular risk. Tirzepatide did not increase the risk of major cardiovascular events in participants with T2D versus controls.

A phase 1 multiple-ascending dose study of tirzepatide in Japanese participants with type 2 diabetes

AIM

To investigate the safety, tolerability, pharmacokinetics (PK), and pharmacodynamics (PD) of tirzepatide in Japanese participants with type 2 diabetes (T2D).

METHODS

This phase 1, double-blind, placebo-controlled, parallel-dose, multiple-ascending dose study randomized participants to once-weekly subcutaneous tirzepatide or placebo. The tirzepatide treatment groups were: 5 mg (5 mg, weeks 1-8), 10 mg (2.5 mg, weeks 1-2; 5 mg, weeks 3-4; 10 mg, weeks 5-8), and 15 mg (5 mg, weeks 1-2; 10 mg, weeks 3-6; 15 mg, weeks 7-8). The primary outcome was tirzepatide safety and tolerability.

RESULTS

Forty-eight participants were randomized. The most frequently reported treatment-emergent adverse events (AEs) were decreased appetite and gastrointestinal AEs, which were generally dose-dependent and mild in severity. The plasma tirzepatide concentration half-life was approximately 5 days. After 8 weeks of treatment, fasting plasma glucose decreased from baseline with tirzepatide versus placebo; the least squares (LS) mean decrease compared with placebo (95% confidence interval [CI]) was 52.7 (35.9-69.6), 69.1 (52.3-85.9), and 68.9 (53.2-84.6) mg/dL in the 5-, 10-, and 15-mg treatment groups, respectively (P < .0001 for all treatment groups). Tirzepatide also resulted in LS mean decreases from baseline versus placebo at 8 weeks in HbA1c up to 1.6% (95% CI 1.2%-1.9%; P < .0001 for all treatment groups) and body weight up to 6.6 kg (95% CI 5.3-7.9; P < .0001 for all treatment groups).

CONCLUSIONS

All tirzepatide doses were well tolerated. The safety, tolerability, PK, and PD profiles of tirzepatide support further evaluation of once-weekly dosing in Japanese people with T2D.

The therapeutic potential of GLP-1 receptor biased agonism

Glucagon-like peptide-1 (GLP-1) receptor agonists are effective treatments for type 2 diabetes as they stimulate insulin release and promote weight loss through appetite suppression. Their main side effect is nausea. All approved GLP-1 agonists are full agonists across multiple signalling pathways. However, selective engagement with specific intracellular effectors, or biased agonism, has been touted as a means to improve GLP-1 agonists therapeutic efficacy. In this review, I critically examine how GLP-1 receptor-mediated intracellular signalling is linked to physiological responses and discuss the implications of recent studies investigating the metabolic effects of biased GLP-1 agonists. Overall, there is little conclusive evidence that beneficial and adverse effects of GLP-1 agonists are attributable to distinct, nonoverlapping signalling pathways. Instead, G protein-biased GLP-1 agonists appear to achieve enhanced anti-hyperglycaemic efficacy by avoiding GLP-1 receptor desensitisation and downregulation, partly via reduced β-arrestin recruitment. This effect seemingly applies more to insulin release than to appetite regulation and nausea, possible reasons for which are discussed. At present, most evidence derives from cellular and animal studies, and more human data are required to determine whether this approach represents a genuine therapeutic advance. LINKED ARTICLES: This article is part of a themed issue on GLP1 receptor ligands (BJP 75th Anniversary). To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v179.4/issuetoc.

Effects of Tirzepatide, a Dual GIP and GLP-1 RA, on Lipid and Metabolite Profiles in Subjects With Type 2 Diabetes

CONTEXT

Tirzepatide substantially reduced hemoglobin A1c (HbA1c) and body weight in subjects with type 2 diabetes (T2D) compared with the glucagon-like peptide 1 receptor agonist dulaglutide. Improved glycemic control was associated with lower circulating triglycerides and lipoprotein markers and improved markers of beta-cell function and insulin resistance (IR), effects only partially attributable to weight loss.

OBJECTIVE

Assess plasma metabolome changes mediated by tirzepatide.

DESIGN

Phase 2b trial participants were randomly assigned to receive weekly subcutaneous tirzepatide, dulaglutide, or placebo for 26 weeks. Post hoc exploratory metabolomics and lipidomics analyses were performed.

SETTING

Post hoc analysis.

PARTICIPANTS

259 subjects with T2D.

INTERVENTION(S)

Tirzepatide (1, 5, 10, 15 mg), dulaglutide (1.5 mg), or placebo.

MAIN OUTCOME MEASURE(S)

Changes in metabolite levels in response to tirzepatide were assessed against baseline levels, dulaglutide, and placebo using multiplicity correction.

RESULTS

At 26 weeks, a higher dose tirzepatide modulated a cluster of metabolites and lipids associated with IR, obesity, and future T2D risk. Branched-chain amino acids, direct catabolic products glutamate, 3-hydroxyisobutyrate, branched-chain ketoacids, and indirect byproducts such as 2-hydroxybutyrate decreased compared to baseline and placebo. Changes were significantly larger with tirzepatide compared with dulaglutide and directly proportional to reductions of HbA1c, homeostatic model assessment 2-IR indices, and proinsulin levels. Proportional to metabolite changes, triglycerides and diglycerides were lowered significantly compared to baseline, dulaglutide, and placebo, with a bias toward shorter and highly saturated species.

CONCLUSIONS

Tirzepatide reduces body weight and improves glycemic control and uniquely modulates metabolites associated with T2D risk and metabolic dysregulation in a direction consistent with improved metabolic health.