Exenatide: pharmacokinetics,clinical use,and future directions

Introduction: The first-in-class glucagon-like peptide-1 receptor agonist (GLP-1RA) exenatide, which was initially approved in 2005, is available in twice-daily (BID) and once-weekly (QW) formulations. Clinical trial data suggest both formulations are effective and safe for patients with type 2 diabetes (T2D), both as monotherapy and as part of combination therapy. Since exenatide was approved, several other GLP-1RAs have become available for clinical use.

Areas covered: Many ongoing clinical trials involving exenatide BID and exenatide QW are investigating new indications (exenatide BID) and new end points and combination therapies (exenatide QW). This review provides an overview of the delivery and pharmacokinetics of both formulations of exenatide, reviews existing data in T2D, and summarizes ongoing investigations.

Expert opinion: Exenatide BID and QW have substantial clinical benefits. Comparisons with other GLP-1RAs demonstrate some differences in efficacy and safety profiles that make assessment of benefit:risk ratios complex. Head-to-head comparisons of QW GLP-1RA formulations may assist in the ranking of GLP-1RAs according to efficacy and safety. Results on the impact of exenatide QW on cardiovascular outcomes are eagerly awaited. The potential clinical utility of exenatide BID in other indications will clarify whether exenatide holds clinical promise in diagnoses other than T2D.     

Cardiovascular safety and benefits of GLP-1 receptor agonists

Introduction: Glucagon-like peptide-1 (GLP-1) receptor agonists (GLP-1RAs) constitute a class of drugs for the treatment of type 2 diabetes, and currently, six different GLP-1RAs are approved. Besides improving glycemic control, the GLP-1RAs have other beneficial effects such as weight loss and a low risk of hypoglycemia. Treatment with the GLP-1RA lixisenatide has been shown to be safe in patients with type 2 diabetes and recent acute coronary syndrome. Furthermore, liraglutide and semaglutide have been shown to reduce cardiovascular (CV) disease (CVD) risk in type 2 diabetes patients with established and/or high risk of CVD. The CV safety of the remaining GLP-1RAs in type 2 diabetes patients with established and/or high risk of CVD remains uncertain, but ongoing CV outcome trials (CVOTs) will elucidate this within a few years.

Areas covered: The aim of this review is to provide an overview of the existing GLP-1RAs with a particular focus on their clinical effects on CV risk factors and their CV safety and benefits.

Expert opinion: Data on the CV risks and benefits associated with GLP-1RA treatment in patients with type 2 diabetes and high risk of CVD are emerging – and look promising (especially for liraglutide and semaglutide). Data from ongoing CVOTs will be crucial for the positioning of the individual GLP-1RAs in the treatment of patients with type 2 diabetes and high risk of CVD. However, the long-term CV safety and the potential of GLP-1RAs to prevent CVD in type 2 diabetes patients with less risk of CVD (e.g. newly diagnosed patients) remain uncertain.     

Sgemaglutide in type 2 diabetes – is it the best glucagon-like peptide 1 receptor agonist (GLP-1R agonist)?

Introduction: Glucagon-like peptide-1 (GLP-1) is produced by the gut, and in a glucose-dependent manner stimulates insulin secretion while inhibiting glucagon secretion, reduces appetite and energy intake, and delays gastric emptying. The GLP-1R agonist semaglutide has recently been registered to treat type 2 diabetes.

Area covered: This review is of semaglutide in type 2 diabetes, and considers which properties of this GLP-1R agonist, may be responsible for its clinical outcome benefits .

Expert opinion: The pharmacokinetics of semaglutide make it ideal for once-weekly dosing. SUSTAIN 6 (Trial to Evaluate Cardiovascular and Other Long-term Outcomes With Semaglutide in Subjects With Type 2 Diabetes) showed that semaglutide 0.5 or 1 mg subcutaneously once-weekly reduced cardiovascular outcomes in subjects with type 2 diabetes and cardiovascular disease or risk, mean age 65 years, baseline HbA1c 8.7% and mean body weight of 92 kg. Although, semaglutide may be a useful drug in this population, it increased retinopathy to a small extent and this needs further investigation. Also, it is not known whether semaglutide will improve cardiovascular outcomes in other populations including those with lower ages, HbA1c values, and body weights similar to those included in the unsuccessful clinical outcome trials with the GLP-1R agonists, lixisenatide and exenatide.     

Rationale for a titratable fixed-ratio co-formulation of a basal insulin analog and a glucagon-like peptide 1 receptor agonist in patients with type 2 diabetes

Objective: Achieving and maintaining recommended glycemic targets, including those for glycated hemoglobin A1c (A1C), is key to improving outcomes in patients with type 2 diabetes (T2D). As fasting plasma glucose and postprandial glucose contribute to overall A1C, targeting both is essential for sustaining glycemic control.

Methods: This review examines the complementary mechanisms of action of glucagon-like peptide 1 (GLP-1) receptor agonists and basal insulin; they both enhance glucose-stimulated insulin release and suppress glucagon secretion. GLP-1 receptor agonists also slow gastric emptying and increase satiety.

Results: Adding a GLP-1 receptor agonist to therapy with a basal insulin analog has been associated with improved overall glycemic control, with comparable risk of hypoglycemia and no weight gain. Titratable fixed-ratio co-formulations of basal insulin and a GLP-1 receptor agonist have been shown to improve glycemic control, with less complex dosing schedules, possibly increasing treatment adherence. The slow titration of fixed-ratio co-formulations has been shown to reduce the occurrence and severity of gastrointestinal adverse events associated with the use of a separate GLP-1 receptor agonist. Titratable fixed-ratio co-formulations also mitigate insulin-associated weight gain, and show a comparable risk of hypoglycemia to basal insulin use alone.

Conclusions: The efficacy and safety of titratable fixed-ratio co-formulations have been demonstrated for insulin degludec/liraglutide and insulin glargine/lixisenatide in the DUAL and LixiLan trials, respectively, in both insulin-naive and -experienced patients. Titratable fixed-ratio co-formulations represent an attractive treatment option for many patients with T2D.     

Efficacy and safety of fixed-ratio combination of insulin degludec and liraglutide (IDegLira) for the treatment of type 2 diabetes

Introduction: Type 2 diabetes (T2D) is a progressive disease with increasing prevalence in most countries. The majority of patients with T2D have inadequate glycaemic control, which increases the risk of diabetic complications later in life. New therapies with improved safety profiles are required to tackle the progressive nature of T2D.

Areas covered: The efficacy and safety profile of IDegLira – a once-daily, fixed-ratio combination of insulin degludec and liraglutide, a glucagon-like peptide-1 receptor agonist (GLP-1RA), for the treatment of T2D – has been extensively evaluated. IDegLira’s phase 3 clinical trial programme builds upon the clinical programmes of its mono-components, and their cardiovascular outcomes trials. The results are described here, focusing on different patient populations and compared with alternative insulin regimens.

Expert opinion: IDegLira provides superior glycaemic control and mitigates the primary adverse effects associated with insulin therapy (weight gain and hypoglycaemia) and GLP-1RAs (gastrointestinal side effects) with no indication of additive effects. Accordingly, co-formulations such as IDegLira are likely to be increasingly preferred over stepwise addition and titration of the individual agents in the management of T2D.     

Adding prandial GLP-1 receptor agonists to basal insulin: a promising option for type 2 diabetes therapy

Background: Diabetes mellitus is a serious and increasingly prevalent condition in Canada and around the world. Treatment strategies have become increasingly complex, with a widening array of pharmacological agents available for glycemic management in type 2 diabetes mellitus (T2DM). New therapies that act in concert with available basal insulins may represent alternatives to basal insulin intensification with prandial or pre-mixed insulin. Glucagon-like peptide-1 receptor agonists (GLP-1 RAs) have recently shown promise as useful additions to basal insulin, with significant reductions in glycated hemoglobin and potentially beneficial effects on body weight. This review will focus on pivotal clinical trials to assess the potential benefits of adding prandial GLP-1 RAs to basal insulin in patients with T2DM.

Methods: Clinical studies combining prandial GLP-1 RAs and basal insulin (published between 2011 and July 2017) were identified and reviewed in PubMed, the Cochrane Central Register of Clinical Trials (Issue 6, June 2017), and clinicaltrials.gov.

Results: Most of the studies presented in this review show that the addition of a prandial GLP-1 RA to basal insulin results in equal or slightly superior efficacy compared to the addition of prandial insulin, together with weight loss and less hypoglycemia.

Conclusions: The results of the studies suggest that a prandial GLP-1 RA as an add-on to basal insulin may be a safe and effective treatment intensification option (vs basal-plus or basal-bolus insulin).     

Efficacy and safety of once-weekly semaglutide for the treatment of type 2 diabetes

Introduction: Type 2 diabetes is a chronic metabolic disease characterized by persistent hyperglycemia resulting from progressive deficient of insulin in patients with a background of insulin resistance. Current treatment algorithms recommended by American Diabetes Association/The European Association for the Study of Diabetes promote a patient-centered approach that takes into account a comprehensive consideration of pharmacological properties of drugs, including glucose-lowering action, effects on body weight, correction on multiple pathophysiologic defects, tolerability, and long-term safety. Glucagon-likepeptide1 (GLP-1) receptor analogues are appealing due to the improved glycemic control in a glucose-dependent manner, modest weight loss and low risk of hypoglycemia.

Areas covered: Semaglutide (Novo Nordisk), a once-weekly GLP-1 analogue, is currently in the phase III clinical trial for the treatment of type 2 diabetes. This article aims to review the pharmacological and clinical profiles of semaglutide based on the available clinical data.

Expert opinion: Semaglutide achieved greater reduction from baseline in HbA_1c in comparison to placebo. The greater proportion of patients in semaglutide group than that in placebo group achieved target HbA_1c <7.0% and <6.5%, respectively. Semaglutide is the second GLP-1 analogue contributing to the reduced bodyweight and improving obesity related complications. More importantly, semaglutide is beneficial to diabetic patients with high cardiovascular risk according to the recently completed phase III trial. The incidence of gastrointestinal adverse effects increased with semaglutide dose.     

A comparative safety review between GLP-1 receptor agonists and SGLT2 inhibitors for diabetes treatment

Introduction: Glucagon-like peptide-1 receptor agonists (GLP-1RA) and sodium glucose cotransporter 2 inhibitors (SGLT2i) are of particular interest in type 2 diabetes treatment strategies, due to their efficacy in reducing HbA1c with a low risk of hypoglycaemia, to their positive effects on body weight and blood pressure and in light of their effects on cardiovascular risk and on nephroprotection emerged from the most recent cardiovascular outcome trials.

Since it is therefore very likely that GLP-1RA and SGLT2i use will become more and more common, it is more and more important to gather and discuss information about their safety profile.

Area Covered: adverse events and the safety concerns most often emerged in trials with GLP-1RA namely, exenatide long acting release (LAR), dulaglutide, liraglutide, semaglutide, lixisenatide or SGLT2i, namely empagliflozin, dapagliflozin, canagliflozin and SGLT2i with an attempt at comparing the safety profiles of molecules of these two classes.

Expert opinion: GLP-1RA and SGLT2i, although each associated with different specific side effects, share a ‘similar’ safety profile and are both drugs relatively easy to handle. The potentially complementary mechanisms of action, the cardio and nephroprotective effects demonstrated by molecules of both classes, make these drugs potentially useful even in add on to each other.     

Preventing and treating kidney disease in patients with type 2 diabetes

Introduction: Chronic kidney disease (CKD) represents a huge burden in patients with type 2 diabetes (T2DM). This review therefore has the aim of assessing the add-on value of new glucose-lowering agents compared or combined with inhibitors of the renin angiotensin aldosterone system (RAAS) on renal outcomes in T2DM patients.

Areas covered: This article first summarizes the results reported with RAAS inhibitors, mainstay of nephroprotection in T2DM with albuminuria. Second, it describes the positive results with glucagon-like peptide-1 receptor agonists (GLP-1RAs) and, even more impressive, sodium-glucose cotransporter type 2 inhibitors (SGLT2is). Third, besides the potential of combined therapies, it briefly considers some new approaches currently in development.

Expert opinion: RAAS inhibitors exert renoprotective effects beyond their blood pressure lowering effects while SGLT2is, and possibly GLP-1RAs, exert nephroprotection independently of their glucose-lowering activity. These effects were demonstrated not only on surrogate endpoints such as albuminuria and estimated glomerular filtration rate decline, but also on hard endpoints, including progression to end-stage renal disease requiring replacement therapy. The underlying mechanisms are different and potentially complementary on glomerular hemodynamics, arguing for combined therapies. Nevertheless, there is still room for new emerging drugs to tackle CKD in T2DM.     

Pharmacokinetic drug evaluation of exenatide for the treatment of type 2 diabetes

Introduction: Glucagon-like peptide-1 (GLP-1) receptor analogs are a group of therapeutic agents which mimic endogenous GLP-1, exerting their effect by the stimulation of the GLP-1 receptor with a wide distribution. Its activation increases insulin releasing dependent on blood glucose levels, suppression of glucagon secretion and a reduction of hepatic glucose output. It delays gastric emptying and increases satiety. Exenatide is the synthetic version of exendin-4, a natural peptide with similar properties to human GLP-1. There are two pharmaceutical forms, for subcutaneous injection: twice daily and once weekly.

Clinical practice guidelines recommend them because of a high efficacy reducing hyperglycemia, low risk of hypoglycemia and a significative weight loss effect. Gastrointestinal adverse events are the most common beside injection site-related. Their cost is the main limitation to use.

Areas covered: We review the recent literature investigating the pharmacokinetics and pharmacodynamics and efficacy-safety studies of exenatide twice daily and once weekly in type 2 diabetes

Expert opinion: GLP-1 receptor analogs are now positioned as an effective and safe drug for the treatment of type 2 diabetes. Exenatide significally reduces HbA1c and fasting plasma glucose. Additionally, it produces moderate weight loss and decreases blood pressure. One weekly formulation may improve compliance while cost is still a limitation. EXSCEL trial has shown that, despite cardiovascular safety, exenatide do not exhibits cardiovascular benefits.     

Potential side effects to GLP-1 agonists: understanding their safety and tolerability

Introduction: Glucagon-like peptide 1 receptor (GLP-1Rx) agonists might elicit unwelcome side effects and concerns have recently been raised about their safety.

Areas covered: Available evidence about safety, tolerability and potential adverse events relative to GLP-1Rx agonists presently used. We searched the MEDLINE database using the terms: ‘GLP-1 receptor agonists’, ‘Incretin therapy side effects’, ‘exenatide’, ‘ liraglutide’, ‘exenatide long-acting release’, ‘lixisenatide’. Articles were selected on the basis of the study design and importance, in the light of authors’ clinical experience and personal judgment. The main safety concern about GLP-1Rx agonists use is the possible association with increased risk of pancreatitis and/or tumors. This concern stems mainly from limited observations in animal models not confirmed in similar studies. Furthermore, clinical studies reporting association between GLP-1Rx agonist use and pancreatitis/cancer are marred by several biases and both clinical trials and post-marketing analyses failed to demonstrate a significant association.

Expert opinion: As stated by both FDA and EMA, the safety concerns emerged so far about GLP-1RX agonists should not affect present prescribing habits. Thus, although a strict data monitoring must be encouraged, they should not prevent access to the benefits of an innovative treatment, such as GLP-1Rx agonists use, to a large diabetic population still confronted with unmet needs.     

Pharmacologic treatment options for type 1 diabetes: what’s new?

Introduction: The expanding variety of insulins, including biosynthetic human insulin and rapid and long-acting insulin analogs, have dramatically transformed the management of type 1 diabetes (T1D) over the past 25 years. Moreover, increasing interest in the use of novel drugs developed for the treatment of type 2 diabetes (T2D) as adjunctive therapies for T1D remains a work in progress.

Areas Covered: We reviewed articles published up to December 2018 in PubMed and ClinicalTrials.gov for recent developments in the pharmacologic treatment of T1D, including inhaled insulin, ultrafast and ultralong-acting insulins and adjunctive therapies including pramlintide, metformin, GLP-1 receptor agonists, DPP-4 inhibitors, SGLT-2, and SGLT1/2 inhibitors.

Expert Opinion: With the creation of ultrafast-acting insulin analogs and very prolonged duration of action of basal insulins, it is possible to more closely mimic physiologic insulin secretion. Adjunctive therapies, likewise, may also overcome some of the abnormal physiology that is a hallmark of T1D. Therefore, individualized consideration of the efficacy of these agents must be measured alongside the potential adverse effects when choosing an adjunctive therapy.     

Individualized,patient-centered use of lixisenatide for the treatment of type 2 diabetes mellitus

Introduction: Type 2 diabetes mellitus (T2DM) is a chronic metabolic disease associated with hyperglycemia, which can lead to serious vascular complications. Current treatment guidelines place particular emphasis on personalization of therapy. Within this guidance, the use of various second-line therapies, including glucagon-like peptide-1 receptor agonists (GLP-1 RAs), is recommended under certain circumstances.

Areas covered: Factors influencing glucose homeostasis, including gastric emptying and the associated cardiovascular (CV) risk when homeostasis is not maintained, are reviewed. Physiology relating to the mechanism of action of GLP-1 RAs is summarized, with a particular focus on lixisenatide. In addition, an overview of efficacy and safety data for lixisenatide is presented and the CV effects of GLP-1 RAs are examined. Finally, the rationale and clinical data supporting the combination of lixisenatide and basal insulin are explored.

Expert opinion: GLP-1 analogs meet a need for better glycemic control, with the added benefits of reduced hypoglycemic risk and body weight. The combination of a short-acting GLP-1 RA, such as lixisenatide, with a basal insulin, exploits the complementary effects of both of these therapies and seems well suited for the treatment of T2DM. However, further studies are needed to establish the associated CV risks and/or benefits of GLP-1 RAs.     

The safety of albiglutide for the treatment of type 2 diabetes

Introduction: Albiglutide is a marketed long acting GLP-1 receptor agonist (GLP-1 RA) administered by weekly injection. It has significantly less gastrointestinal side effects than other GLP-1 RAs in current use but does not improve HbA1c or promote weight loss to the same extent as competitor agents such as liraglutide.

Area Covered: The safety of albiglutide is discussed. The review encompassed a search of PubMed and a thorough analysis of the European Union and US Food and Drug Administration approval documents.

Expert Opinion: Unlike competitor agents, the gastrointestinal side effects of albiglutide are not much greater than placebo. It has been studied and appears safe at all stages of renal failure. There exists concern about an imbalance of pancreatitis cases in the approval program as well as injection site reactions which led to discontinuance of therapy in up to 2% of participants. A large long term study now underway will determine if albiglutide, with its relatively favorable GI tolerance, has a place in the treatment of patients with increased risk of cardiovascular events.     

Safety and tolerability of glucagon-like peptide-1 receptor agonists: unresolved and emerging issues

Introduction: Glucagon-like peptide-1 receptor agonists (GLP-1 RAs) are a mainstay of treatment options for type 2 diabetes. They contribute to lowering blood glucose levels, generally have a favorable tolerability profile, and can be used alone or in combination with other antidiabetic agents. Based on the duration of their effects, GLP-1 RAs can be divided into two classes: short-acting and long-acting. Differences exist between these sub-classes, and between each drug, in terms of pharmacokinetic and pharmacodynamic profiles. Therefore, prescribers cannot necessarily assume GLP-1 RA ‘class effects’, especially in terms of tolerability.

Areas covered: This article reviews the published data on the safety and tolerability of currently available GLP-1 RAs and, recognizing the importance of safety profiles when selecting the appropriate treatment for each patient, examines the clinical implications of the differences between the drugs in this class. Cardiovascular safety, gastrointestinal tolerability, and tolerability in elderly patients are discussed as specific areas of interest to prescribers selecting between GLP-1 RAs for their patients.

Expert opinion: Although further research is needed, the current evidence offers the potential to tailor treatment more accurately to each patient. Ultimately, this may improve adherence and persistence, thereby improving glycemic control and, in turn, reducing the risk of macro- and micro-vascular complications.     

Cardiovascular safety of liraglutide for the treatment of type 2 diabetes

Introduction: Liraglutide is a GLP-1 RA that is an option for treatment of T2DM. Typical of all new glucose-lowering agents, its CV safety profile is of great interest.

Areas covered: This article outlines the efficacy of the GLP-1 RA liraglutide from RCTs, moving through the pivotal phase 3 LEAD trials, and subsequent meta-analyses to assess CV safety. This review describes evolution of regulatory requirements to obtain safety information through dedicated CVOTs.

Expert opinion: Since the FDA mandated that CV outcomes for new diabetes therapies should be assessed via a dedicated CVOT, opinion of their utility in T2DM evolved from cynicism through to enthusiasm. In LEADER, liraglutide became the second modern glucose-lowering agent to demonstrate significant CV benefit. CVOTs are now providing important answers, highlighting the CV benefits of modern glucose-lowering agents, but also raising several questions, notably whether the effects seen with liraglutide and empagliflozin are class-effects or are unique to these molecules. Furthermore it is unknown if these results in patients with high CV risk are applicable to all patients with T2DM, and should be incorporated into new treatment guidelines. In our view it’s prudent to suggest that CVOT findings cannot currently be extrapolated to the whole T2DM population.     

Antidiabetic agents and cardiovascular outcomes in patients with heart diseases

Introduction: This article reviews evidence of the benefits and risk of antidiabetic agents in cardiovascular (CV) outcomes, with a focus on medications approved by the FDA since 2008.

Study selection: Peer-reviewed articles were identified from MEDLINE and Current Content databases (both 1966 to 1 October 2016) using the search terms insulin, metformin, rosiglitazone, pioglitazone, glyburide, glipizide, glimepiride, acarbose, miglitol, albiglutide, exenatide, liraglutide, lixisenatide, dulaglutide, pramlintide, meglitinide, alogliptin, linagliptin, saxagliptin, sitagliptin, canagliflozin, dapagliflozin, empagliflozin, colesevalam, bromocriptine, mortality, myocardial infarction (MI), heart failure (HF), and stroke. Trials were included if they were randomized clinical trials evaluating adult patients (≥18 years) with type 2 diabetes; had a period of intervention and follow-up of ≥12 months; and assessed CV outcomes (CV death, fatal/non-fatal MI or HF) as endpoints. Twenty-three randomized trials were included.

Antidiabetic agents: Of agents approved prior to 2008, metformin has not been associated with measurable harm in patients with diabetes in terms of mortality and CV events (and has a trend of benefit). Controversial results existed with the use of sulfonylureas and thiazolidinediones (TZDs) for CV outcomes. Among agents approved after 2008, liraglutide and empagliflozin have been shown to be superior to placebo in improving CV outcomes.

Conclusions: The FDA regulatory mandate to demonstrate CV safety in order to approve new diabetes drugs led to an increase in the number of CV outcome trials. However, these trials have placebo-controlled, non-inferiority designs aiming to show absence of CV toxicity. More studies are needed to address other questions, including comparative effectiveness, and longer-term risk versus benefits.     

The pharmacological management of metabolic syndrome

Introduction: The metabolic syndrome includes a constellation of several well-established risk factors, which need to be aggressively treated in order to prevent overt type 2 diabetes and cardiovascular disease. While recent guidelines for the treatment of individual components of the metabolic syndrome focus on cardiovascular benefits as resulted from clinical trials, specific recent recommendations on the pharmacological management of metabolic syndrome are lacking. The objective of present paper was to review the therapeutic options for metabolic syndrome and its components, the available evidence related to their cardiovascular benefits, and to evaluate the extent to which they should influence the guidelines for clinical practice.

Areas covered: A Medline literature search was performed to identify clinical trials and meta-analyses related to the therapy of dyslipidemia, arterial hypertension, glucose metabolism and obesity published in the past decade.

Expert commentary: Our recommendation for first-line pharmacological are statins for dyslipidemia, renin-angiotensin-aldosteron system inhibitors for arterial hypertension, metformin or sodium/glucose cotransporter 2 inhibitors or glucagon-like peptide 1 receptor agonists (GLP-1RAs) for glucose intolerance, and the GLP-1RA liraglutide for achieving body weight and waist circumference reduction.