Day-long subcutaneous infusion of exenatide lowers glycemia in patients with type 2 diabetes

Oral delivery of exenatide-loaded hybrid zein nanoparticles for stable blood glucose control and β-cell repair of type 2 diabetes mice

BACKGROUND

Exenatide is an insulinotropic peptide drug for type 2 diabetes treatment with low risk of hypoglycemia, and is administrated by subcutaneous injection. Oral administration is the most preferred route for lifelong treatment of diabetes, but oral delivery of peptide drug remains a significant challenge due to the absorption obstacles in gastrointestinal tract. We aimed to produce exenatide-loaded nanoparticles containing absorption enhancer, protectant and stabilizer using FDA approved inactive ingredients and easy to scale-up method, and to evaluate their long-term oral therapeutic effect in type 2 diabetes db/db mice.

RESULTS

Two types of nanoparticles, named COM NPs and DIS NPs, were fabricated using anti-solvent precipitation method. In COM NPs, the exenatide was complexed with cholic acid and phosphatidylcholine to increase the exenatide loading efficiency. In both nanoparticles, zein acted as the cement and the other ingredients were embedded in zein nanoparticles by hydrophobic interaction. Casein acted as the stabilizer. The nanoparticles had excellent lyophilization, storage and re-dispersion stability. Hypromellose phthalate protected the loaded exenatide from degradation in simulated gastric fluid. Cholic acid promoted the intestinal absorption of the loaded exenatide via bile acid transporters. The exenatide loading efficiencies of COM NPs and DIS NPs were 79.7% and 53.6%, respectively. The exenatide oral pharmacological availability of COM NPs was 18.6% and DIS NPs was 13.1%. COM NPs controlled the blood glucose level of the db/db mice well and the HbA_1c concentration significantly decreased to 6.8% during and after 7 weeks of once daily oral administration consecutively. Both DIS NPs and COM NPs oral groups substantially increased the insulin secretion by more than 60% and promoted the β-cell proliferation by more than 120% after the 7-week administration.

CONCLUSIONS

Both COM NPs and DIS NPs are promising systems for oral delivery of exenatide, and COM NPs are better in blood glucose level control than DIS NPs. Using prolamin to produce multifunctional nanoparticles for oral delivery of peptide drug by hydrophobic interaction is a simple and effective strategy.

Pharmacokinetics of Exenatide in nonhuman primates following its administration in the form of sustained-release PT320 and Bydureon

The time-dependent (30 min - day 84) plasma profile of PT320, a sustained-release (SR)-Exenatide formulation under clinical development for treatment of neurodegenerative disorders, was evaluated in nonhuman primates after a single subcutaneous dose and was compared to Bydureon. Exenatide release from PT320 exhibited a triphasic pharmacokinetic profile. An initial peak occurred at 3 hr post-administration, a secondary peak at 5 days, and achievement of Exenatide steady-state plasma levels from day 10–28. Systemic exposure increased across PT320 doses, and Exenatide levels were maintained above the therapeutic threshold prior to achieving a steady-state. In contrast, Exenatide release from Bydureon exhibited a biphasic profile, with an initial plasma peak at 3 hr, followed by a rapid decline to a sub-therapeutic concentration, and a gradual elevation to provide a steady-state from day 35–49. Exenatide total exposure, evaluated from the area under the time-dependent Exenatide concentration curve, was similar for equivalent doses of PT320 and Bydureon. The former, however, reached and maintained steady-state plasma Exenatide levels more rapidly, without dipping to a sub-therapeutic concentration. Both SR-Exenatide formulations proved well-tolerated and, following a well-regulated initial release burst, generated steady-state plasma levels of Exenatide, but with PT320 producing continuous therapeutic Exenatide levels and more rapidly reaching a steady-state.

Long-term oral administration of Exendin-4 to control type 2 diabetes in a rat model

Exendin-4 is a glucagon-like peptide-1 (GLP-1) receptor agonist and potent insulinotropic agent for type 2 diabetes patients; however, its therapeutic utility is limited due to the frequent injections required. Long-acting agonists reduce the number of injections, but they can compromise potency. In this study, chondroitin sulfate-g-glycocholic acid-coated and Exendin-4 (Ex-4)-loaded liposomes (EL-CSG) were prepared for oral administration of Ex-4. The Ex-4 loading efficiency was 77% and the loading content in the nanoparticles was 1 wt-%. In rat models, a single oral dose (200 μg/kg) of EL-CSG showed a relative oral bioavailability of 19.5%, compared with subcutaneous administration (20 μg/kg), and sustained pharmacokinetics for up to 72 h. The overall long-term pharmacodynamic effects, assessed by hemoglobin A1c (HbA1c), body weight, and blood lipid concentrations, of daily oral EL-CSG (300 μg/kg) for four weeks were equivalent to or better than daily subcutaneous injections of free Ex-4 solution (20 μg/kg).

Exenatide substantially improves proinsulin conversion and cell survival that augment Ins2+/Akita beta cell function

Proinsulin folding imperfections cause extensive beta-cell defects known in diabetes. Here, we investigated whether exenatide can alleviate such defects in proinsulin conversion, beta-cell survival, and insulin secretion, in the Ins2^+/Akita beta-cells that have a spontaneous mutation (Cys 96 Tyr) in the insulin 2 gene caused dominant negative misfolding problem. 15 or 120 min exenatide administration substantially improves glucose-stimulated insulin secretion, marked in the secreted insulin levels and proinsulin/insulin ratio. This improvement is mainly due to enhanced conversion of proinsulin to insulin, having nothing to do with the prohormone convertase PC1/3 and PC2 levels. The 15 min improvement is calcium-independent. The 120 min improvement is linked to calcium and/or cAMP dependent mechanisms. This efficacy is validated during longer treatment and in Akita islets. Exenatide improves Ins2^+/Akita beta-cell survival and Akita mouse's glucose tolerance. The results suggest a potential of incretin mimetics in alleviating defective proinsulin conversion and other proinsulin misfolding consequences.

Efficacy and Safety of Multiple Doses of Exenatide Once-Monthly Suspension in Patients With Type 2 Diabetes: A Phase II Randomized Clinical Trial

OBJECTIVE

This study investigated the efficacy and safety of multiple exenatide once-monthly suspension (QMS) doses of exenatide-containing microspheres in Miglyol referenced against the clinical dose of exenatide once-weekly (QW) microspheres in aqueous solution.

RESEARCH DESIGN AND METHODS

In this phase II, randomized, controlled, single-blind study, 121 adults (∼30/arm) with type 2 diabetes and HbA1c 7.1-11.0% (54-97 mmol/mol) were randomized 1:1:1:1 to subcutaneous exenatide QW 2 mg (self-administered) or exenatide QMS 5, 8, or 11 mg (caregiver-administered) for 20 weeks. The primary end point was change in HbA1c.

RESULTS

At baseline, mean age was 50 years, HbA1c was 8.5% (69 mmol/mol), fasting plasma glucose (FPG) was 184 mg/dL, and body weight was 98 kg. At week 20, mean ± SD HbA1c reductions were -1.54% ± 1.26% with exenatide QW and -1.29% ± 1.07%, -1.31% ± 1.66%, and -1.45% ± 0.93% with exenatide QMS 5, 8, and 11 mg, respectively (evaluable population: n = 110). There were no significant differences in HbA1c reductions among the exenatide QMS doses. FPG reductions were -34 ± 48 mg/dL with exenatide QW and -25 ± 43, -30 ± 52, and -49 ± 49 mg/dL with exenatide QMS 5, 8, and 11 mg, respectively. Weight decreased with all treatments. For exenatide QMS, nausea (16.7-23.3%) and headache (16.7-26.7%) were the most common adverse events. No major or minor hypoglycemia occurred.

CONCLUSIONS

All doses of exenatide QMS resulted in efficacy and tolerability profiles consistent with exenatide QW. These results combined with pharmacokinetic and pharmacodynamic modeling could inform dose selection for further development.

Onset of Glycemic and Weight Outcomes in Patients Initiating Exenatide Once Weekly: The Relationship of Exenatide Exposure with Efficacy over the First 24 Weeks of Treatment

INTRODUCTION

Exenatide is gradually released from exenatide once weekly (QW) microspheres, and at steady state, consistently controls glycated hemoglobin (HbA1c) in patients with type 2 diabetes (T2D). This post hoc analysis examined the timing to onset of clinical responses and their correlations with exenatide concentrations after initiation of exenatide QW in patients with T2D.

METHODS

Trial data were retrospectively analyzed to explore the early clinical responses to exenatide QW, including the relationship of exenatide concentration with its effects on efficacy [fasting plasma glucose (FPG), HbA1c, and body weight] and tolerability (nausea and vomiting). Exenatide QW efficacy and tolerability data were from DURATION-5, a 24-week, randomized, comparator-controlled trial [intent-to-treat (ITT) population]. Exenatide concentrations were measured in a patient subset (pharmacokinetic population).

RESULTS

In the ITT (n = 129)/pharmacokinetic (n = 72) populations, baseline FPG, HbA1c, and body weight were 173/173 mg/dL, 8.5%/8.4%, and 97/98 kg, respectively. Exenatide concentrations gradually increased until reaching steady state at week 8. By week 4, the FPG reduction (-32.4 mg/dL) was 94% of the week 24 reduction (-34.6 mg/dL). Reductions in HbA1c began by week 4 (-0.6%) and stabilized by week 14 (week 24: -1.6%). Weight reduction at week 4 was -0.7 kg and decreased further (week 24: -2.3 kg). Peak nausea (7.2%) and vomiting (2.4%) occurred at weeks 6-8, declining thereafter.

CONCLUSION

Clinically relevant responses to exenatide QW were evident by week 4, after exenatide concentration passed the therapeutic threshold but before steady state was achieved.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT00877890.

FUNDING

AstraZeneca.

Pharmacokinetics and Tolerability of Exenatide Delivered by 7-Day Continuous Subcutaneous Infusion in Healthy Volunteers

INTRODUCTION

Small peptides are approved as treatments for type 2 diabetes mellitus and may have utility in metabolic diseases. These peptides often have short half-lives requiring delivery either as a sustained-release formulation or via a device. The opportunity to study their pharmacokinetics using simple solution formulations delivered by continuous subcutaneous infusion may facilitate the drug development process.

METHODS

Here, we investigated the systemic exposure of an exemplar peptide (exenatide) when infused in healthy subjects using a Paradigm(®) Revel™ insulin infusion pump (Medtronic MiniMed). Four infusion regimens were tested: Constant 24-h infusion (16.5 μg/day), constant 7-day infusion (25.5 μg/day in Cohort 2), and two different 7-day escalation regimens (ranging from 7 to 58.5 μg/day in Cohort 1 and 25.5-58.5 μg/day in Cohort 3).

RESULTS

While the overall exenatide pharmacokinetics were in line with those expected, the observed within-subject concentration variability was considerable.

CONCLUSION

Our work identifies sources of potential pharmacokinetic variability relating to the method of delivery and the drug's formulation that will be valuable to investigators contemplating the delivery of peptides via insulin infusion pumps.

FUNDING

GlaxoSmithKline.

TRIAL REGISTRATION

ClinicalTrials.gov number, NCT01857895.

Target-mediated pharmacokinetic/pharmacodynamic model based meta-analysis and dosing regimen optimization of a long-acting release formulation of exenatide in patients with type 2 diabetes mellitus

A hybrid pharmacokinetic/pharmacodynamic (PK/PD) model with extended-release (ER) process and target mediated drug disposition (TMDD) was developed for exenatide ER to account for its complex absorption process and glucagon-like peptide 1 receptor (GLP-1R)-mediated non-linear PK behaviors along with its influences to fasting plasma glucose (FPG) and hemoglobin A1c (HbA1c). Using hybrid PK/PD model, simulations were done to explore the potential dosing regimens which could achieve likelihood of more pharmacodynamic exposure with respect to FPG and HbA1c over a much shorter period compared with the currently used treatment protocol. The mean PK/PD data about exenatide ER for type 2 diabetes mellitus (T2DM) were digitized from the publications, and the hybrid PK/PD model was performed using the Monolix 4.3 program. The plasma concentration-time and FPG/HbA1c-time profiles for exenatide ER subcutaneously administrated to patients with T2DM were well described by this hybrid model. Monte Carlo simulation was applied to mimic the PK profiles when higher loading dose 7.5 and 5.0 mg exenatide ER were subcutaneously administrated with different dosing intervals at the first 3 weeks of 30-week treatment. Two potentially optimizing schedules could improve the likelihood of achieving much more FPG and HbA1c exposures than currently used clinical treatment protocol.

Once weekly exenatide: efficacy, tolerability and place in therapy

Exenatide once weekly is the first glucose-lowering agent available to patients with type 2 diabetes mellitus (T2DM) which is administered once per week. This long-acting formulation contains the same active ingredient as exenatide twice daily, except that the exenatide is encapsulated in dissolvable microspheres. Following subcutaneous injection, exenatide once weekly microspheres remain in place under the skin and slowly degrade, releasing active exenatide continuously into circulation. In randomized clinical trials, exenatide once weekly was associated with significant glycaemic improvement and moderate weight loss in patients with T2DM when administered as monotherapy or in combination with a variety of oral antidiabetic agents. Exenatide once weekly also lowered blood glucose more effectively than titrated basal insulin in patients on metformin or metformin plus sulphonylurea background therapy. Gastrointestinal side effects (nausea, vomiting and diarrhoea) were the most common tolerability issues associated with exenatide once weekly administration, but they occurred at lower rates than in patients on other glucagon-like peptide receptor agonists (i.e., exenatide twice daily or liraglutide). Issues regarding the place of exenatide once weekly in T2DM pharmacotherapy are discussed.

Do current incretin mimetics exploit the full therapeutic potential inherent in GLP-1 receptor stimulation?

Glucagon-like peptide-1 (GLP-1) receptor agonists (RAs) are incretin-derived glucose-lowering agents that have been used for the treatment of type 2 diabetes since 2007. Agents such as exenatide (short-acting and once weekly preparations), liraglutide, taspoglutide, albiglutide and lixisenatide lower fasting glucose and HbA1c upon subcutaneous injection, leading to glycaemic control that is equivalent to, or better than, that observed with other oral glucose-lowering agents or bedtime insulin. However, varying proportions of patients report nausea and vomiting, adverse events that typically narrow the therapeutic dose range. Furthermore, GLP-1 RAs reduce fasting glucose to a clinically meaningful extent, but not into the normal range. In contrast, where GLP-1 is administered as a short-term intravenous infusion, a full normalisation of glucose concentrations (approximately 5 mmol/l) has been observed without any risk of gastrointestinal side effects. Subcutaneous infusions or injections of GLP-1 are much less effective. The present analysis relates the proportion of patients who report nausea following treatment with GLP-1 and GLP-1 RAs to the clinical effectiveness of the treatment (represented by the fasting glucose concentration achieved with treatment). The results suggest that GLP-1 RAs injected into the subcutaneous compartment do not exploit the full potential inherent in GLP-1 receptor activation. Reasons for this may include modifications of the peptide molecules in the subcutaneous environment or high local concentrations triggering side effects through GLP-1 receptors on autonomic nerves in subcutaneous adipose tissue. Elucidation of the mechanisms underlying differential responses to GLP-1/GLP-1 RAs administered intravenously vs subcutaneously may help to develop improved agents or modes of administration that are more effective and have fewer side effects.

Exendin-4, a glucagon-like peptide-1 receptor agonist, prevents osteopenia by promoting bone formation and suppressing bone resorption in aged ovariectomized rats

Osteoporosis mainly affects postmenopausal women and older men. Gastrointestinal hormones released after meal ingestion, such as glucose-dependent insulinotropic peptide (GIP) and glucagon-like peptide (GLP)-2, have been shown to regulate bone turnover. However, whether GLP-1, another important gastrointestinal hormone, and its analogues also have antiosteoporotic effects, especially in aged postmenopausal situation, has not been confirmed. In the present study, we evaluated the effects of the GLP-1 receptor agonist exendin-4 on ovariectomy (OVX)-induced osteoporosis in old rats. Twelve-month-old female Sprague-Dawley rats were subjected to OVX, and exendin-4 was administrated 4 weeks after the surgery and lasted for 16 weeks. Bone characters and related serum and gene biomarkers were analyzed. Sixteen weeks of treatment with exendin-4 slowed down body weight gain by decreasing fat mass and prevented the loss of bone mass in old OVX rats. Exendin-4 also enhanced bone strength and prevented the deterioration of trabecular microarchitecture. Moreover, exendin-4 decreased the urinary deoxypyridinoline (DPD)/creatinine ratio and serum C-terminal cross-linked telopeptides of type I collagen (CTX-I) and increased serum alkaline phosphatase (ALP), osteocalcin (OC), and N-terminal propeptide of type 1 procollagen (P1NP) levels, key biochemical markers of bone turnover. Interestingly, gene expression results further showed that exendin-4 not only inhibited bone resorption by increasing the osteoprotegerin (OPG)/receptor activator of NF-κB ligand (RANKL) ratio, but also promoted bone formation by increasing the expression of OC, Col1, Runx2, and ALP, which exhibited dual regulatory effects on bone turnover as compared with previous antiosteoporotic agents. In conclusion, these findings demonstrated for the first time the antiosteoporotic effects of exendin-4 in old OVX rats and that it might be a potential candidate for treatment of aged postmenopausal osteoporosis.

Evolution of exenatide as a diabetes therapeutic

Type 2 diabetes (T2DM) is a disease of epidemic proportion associated with significant morbidity and excess mortality. Optimal glucose control reduces the risk of microvascular and possibly macrovascular complications due to diabetes. However, glycemic control is rarely optimal and several therapeutic interventions for the treatment of diabetes cause hypoglycemia and weight gain; some may exacerbate cardiovascular risk. Exenatide (synthetic exendin-4) is a glucagon- like peptide-1 receptor (GLP-1R) agonist developed as a first-in-class diabetes therapy. This review presents an overview of the evolution of exenatide as a T2DM treatment, beginning with the seminal preclinical discoveries and continuing through to clinical pharmacology investigations and phase 3 clinical trials. In patients with T2DM, exenatide enhanced glucose-dependent insulin secretion, suppressed inappropriately elevated glucagon secretion, slowed gastric emptying, and enhanced satiety. In controlled phase 3 clinical trials ranging from 12 to 52 weeks, 10-mcg exenatide twice daily (ExBID) reduced mean HbA1c by -0.8% to -1.7% as monotherapy or in combination with metformin (MET), sulfonylureas (SFU), and/or thiazolidinediones (TZD); with mean weight losses of -1.2 kg to -8.0 kg. In controlled phase 3 trials ranging from 24 to 30 weeks, a 2-mg once-weekly exenatide formulation (ExQW) reduced mean HbA1c by -1.3% to -1.9%, with mean weight reductions of -2.3 to -3.7 kg. Exenatide was generally well-tolerated. The most common side effects were gastrointestinal in nature, mild, and transient. Nausea was the most prevalent adverse event. The incidence of hypoglycemia was generally low. By building upon early observations exenatide was successfully developed into an effective diabetes therapy.

Comparison of extended release GLP-1 receptor agonist therapy versus sitagliptin in the management of type 2 diabetes

Exenatide once weekly (EQW), the first glucose-lowering agent for type 2 diabetes that is dosed one time per week, contains exenatide encapsulated in microspheres of a dissolvable matrix, which release active agent slowly and continuously into the circulation following subcutaneous injection. In two direct head-to-head comparisons, EQW resulted in better long-term glucose control, greater reductions in fasting plasma glucose, and more significant weight loss than sitagliptin. In other trials, glucose-lowering effects of EQW compared favorably with those of metformin, pioglitazone, and basal insulin. Patients on EQW exhibited a higher incidence of nausea than those on sitagliptin, although gastrointestinal adverse events occurred primarily during the first 6-8 weeks of therapy and declined thereafter. EQW was also associated with a lower incidence of nausea than two other glucagon-like peptide-1 receptor agonists, exenatide twice daily and liraglutide. Mild hypoglycemic episodes were uncommon with EQW, although risk of hypoglycemia increased in combination with sulfonylureas. When choosing between EQW and a dipeptidyl peptidase-4 (DPP-4) inhibitor, such as sitagliptin, clinicians and patients should consider the differences between the two medications in terms of glucose control (EQW superior to DPP-4 inhibitors), weight control (EQW superior to DPP-4 inhibitors), gastrointestinal tolerability during treatment initiation (EQW inferior to DPP-4 inhibitors), and mode of administration (once-weekly subcutaneous administration versus once-daily oral administration).

GLP-1 based therapies: differential effects on fasting and postprandial glucose

Glucagon-like peptide-1 (GLP-1), a gut-derived hormone secreted in response to nutrients, has several glucose and weight regulating actions including enhancement of glucose-stimulated insulin secretion, suppression of glucagon secretion, slowing of gastric emptying and reduction in food intake. Because of these multiple effects, the GLP-1 receptor system has become an attractive target for type 2 diabetes therapies. However, GLP-1 has significant limitations as a therapeutic due to its rapid degradation (plasma half-life of 1-2 min) by dipeptidyl peptidase-4 (DPP-4). Two main classes of GLP-1-mediated therapies are now in use: DPP-4 inhibitors that reduce the degradation of GLP-1 and DPP-4-resistant GLP-1 receptor (GLP-1R) agonists. The GLP-1R agonists can be further divided into short- and long-acting formulations which have differential effects on their mechanisms of action, ultimately resulting in differential effects on their fasting and postprandial glucose lowering potential. This review summarizes the similarities and differences among DPP-4 inhibitors, short-acting GLP-1R agonists and long-acting GLP-1R agonists. We propose that these different GLP-1-mediated therapies are all necessary tools for the treatment of type 2 diabetes and that the choice of which one to use should depend on the specific needs of the patient. This is analogous to the current use of modern insulins, as short-, intermediate- and long-acting versions are all used to optimize the 24-h plasma glucose profile as needed. Given that GLP-1-mediated therapies have advantages over insulins in terms of hypoglycaemic risk and weight gain, optimized use of these compounds could represent a significant paradigm shift for the treatment of type 2 diabetes.

Neuroprotective effect of the glucagon-like peptide-1 receptor agonist, synthetic exendin-4, in streptozotocin-induced diabetic rats

BACKGROUND AND PURPOSE

Glucagon-like peptide-1 (GLP-1) receptors are widely expressed in neural tissues and diminish neuronal degeneration or induce neuronal differentiation. The aim of this study was to investigate the effect of the GLP-1 pathway on peripheral nerves in streptozotocin-induced diabetic rats.

EXPERIMENTAL APPROACH

Diabetic and nondiabetic rats were treated with the GLP-1 receptor agonist, synthetic exendin-4 (i.p., 1 nmol·kg(-1)·day(-1)) or placebo for 24 weeks, and current perception threshold values, cAMP levels and nerve fibre size in the sciatic nerve were measured. We also investigated GLP-1 receptor expression, quantitative changes in PGP9.5-positive intraepidermal nerve fibres and cleaved caspase 3-stained Schwann cells by immunohistochemistry.

KEY RESULTS

GLP-1 receptor expression was detected in the sciatic nerve and skin. After exendin-4 treatment, the increase seen in current perception threshold values at 2000 and 250 Hz in diabetic rats was reduced. Also, the decrease in myelinated fibre size or axon/fibre area ratio in the sciatic nerve and the loss of intraepidermal nerve fibre in the skin of diabetic rats were ameliorated. These responses were closely associated with the attenuation of Schwann cell apoptosis and improvement in the cAMP level in exendin-4-treated diabetic rats, compared with placebo-treated animals.

CONCLUSION AND IMPLICATIONS

Synthetic exendin-4 may prevent peripheral nerve degeneration induced by diabetes in an animal model, supporting the hypothesis that GLP-1 may be useful in peripheral neuropathy. The neuroprotection is probably attributable to GLP-1 receptor activation, antiapoptotic effects and restoration of cAMP content.

Encapsulation of exenatide in poly-(D,L-lactide-co-glycolide) microspheres produced an investigational long-acting once-weekly formulation for type 2 diabetes

Exenatide once-weekly (EQW [2 mg s.c.]) is under development as monotherapy as an adjunct to diet and exercise or as a combination therapy with an oral antidiabetes drug(s) in adults with type 2 diabetes. This long-acting formulation contains the active ingredient of the original exenatide twice-daily (EBID) formulation encapsulated in 0.06-mm-diameter microspheres of medical-grade poly-(D,L-lactide-co-glycolide) (PLG). After mechanical suspension and subcutaneous injection by the patient, EQW microspheres hydrate in situ and adhere to one another to form an amalgam. A small amount of loosely bound surface exenatide, typically less than 1%, releases in the first few hours, whereas drug located in deeper interstices diffuses out more slowly (time to maximum, ~2 weeks). Fully encapsulated exenatide (i.e., drug initially inaccessible to diffusion) releases over a still longer period (time to maximum, ~7 weeks) as the PLG matrix hydrolyzes into lactic acid and glycolic acid, which are subsequently eliminated as carbon dioxide and water. For EQW, plasma exenatide concentrations reach the therapeutic range by 2 weeks and steady state by 6-7 weeks. This gradual approach to steady state seems to improve tolerability, as nausea is less frequent with EQW than EBID. EQW administrations may be associated with palpable skin nodules that generally resolve without further medical intervention. In comparative trials, EQW improved hemoglobin A1c more than EBID, sitagliptin, pioglitazone, or insulin glargine and reduced fasting plasma glucose more than EBID. Weight loss due to EQW or EBID was similar. EQW is the first glucose-lowering agent that is administered once weekly.

The Current Status of Exenatide Once Weekly

Type 2 diabetes mellitus (T2DM) is a chronic, progressive metabolic disorder that is associated with long-term microvascular (retinopathy, neuropathy and nephropathy) and macrovascular (myocardial infarction, stroke, peripheral arterial disease) complications. Both the prevalence of T2DM and the cost of its long-term complications have driven the focus and emphasis on treatments aimed at reducing hyperglycemia and controlling hypertension and dyslipidemia while minimizing hypoglycemia and weight gain. Exenatide twice daily, the first GLP-1R agonist approved by the US Food and Drug Administration (FDA) and European Medicines Agency (EMEA), has been shown to reduce hemoglobin A1C, lower fasting and postprandial plasma blood glucose concentrations as well as reduce body weight without causing significant hypoglycemia. However, its current formulation requires twice daily subcutaneous injections and does not provide continuous GLP-1R activation. Therefore, a long-acting release form of exenatide has been developed for use as a once-weekly injection, providing for convenient administration and continuous GLP-1R activation. This review covers the currently published data on this new formulation including mechanism of action, pharmacokinetics, efficacy and comparison trials to other commonly used anti-diabetic agents.

Exenatide once weekly: clinical outcomes and patient satisfaction

BACKGROUND

Type 2 diabetes mellitus (T2DM) is a complex disorder in which interactions between environmental and genetic factors result in the development of insulin resistance (in most cases) and progressive pancreatic β-cell failure. The currently available oral anti-diabetes treatments are effective as monotherapy; however, due to the progressive decline in β-cell function, most patients will require the use of combination therapy and eventually insulin to reach glycemic targets. These therapeutic options are not without undesirable side effects such as weight gain and hypoglycemia. Furthermore, T2DM is associated with impaired quality of life (QOL) and poor compliance with treatment. Hence, there is a need for anti-diabetes agents that result in sustained improvements in glycemic control without hypoglycemia or weight gain and have a positive impact on patients QOL and thereby hopefully improve compliance. Incretin-based therapy is the latest addition to anti-diabetes treatments which addresses some of the shortcomings of older treatments.

AIMS

To review the evidence for the use of exenatide once-weekly.

METHODS

We have searched Medline using the terms "exenatide", "exenatide once-weekly", and "exenatide LA".

RESULTS

Exenatide once-weekly is an incretin mimetic that is currently undergoing phase 3 clinical trials, and has been shown to improve glycemic parameters (HbA(1c) and fasting and postprandial glucose levels), with low risk of hypoglycemia, causes weight loss, and use was associated with improvements in patient satisfaction which might have a positive impact on treatment compliance.

CONCLUSIONS

Exenatide once-weekly is effective, well tolerated in patients with T2DM and should be a useful addition to the available range of anti-diabetes treatments.

Glycaemic control in type 2 diabetes: targets and new therapies

Type 2 diabetes mellitus (T2DM) is a worldwide public health challenge. Despite the availability of many antidiabetes agents and pharmacotherapies targeting cardiovascular risk factors, the morbidity, mortality and economic consequences of T2DM are still a great burden to patients, society, health care systems and the economy. The need for new therapies for glycaemic control is compounded by the fact that existing treatments have limitations either because of their side effects (particularly weight gain and hypoglycaemia) or contraindications that limit their use. Furthermore, none of the current therapies have a significant impact on disease progression. Incretin-based therapies offer a new therapeutic approach to the management of T2DM, and there are also several even newer therapies in development. There are two groups of incretin-based therapies currently available; dipeptidyl peptidase-4 (DPP-4) inhibitors and GLP-1 analogues/mimetics. The former are given orally while the latter subcutaneously. These drugs result in glucose-dependent insulin secretion and glucose-dependent glucagon suppression, with consequent low risk of hypoglycaemia when used as mono- or combination therapy (except when used with sulphonylureas). In addition, they are either weight neutral in the case of DPP-4 inhibitors or cause weight loss in the case of incretin mimetics/analogues. Furthermore, animal studies have shown that these agents prolong beta cell survival which offers the theoretical possibility of slowing the progression to T2DM. In this article we will review the currently available antidiabetes agents with particular emphasis on incretin-based and future therapies. In addition, we will review and discuss the evidence relating to glycaemic control and cardiovascular disease.

Safety, tolerability, pharmacokinetics, and pharmacodynamics of exenatide once weekly in Japanese patients with type 2 diabetes

This randomized, placebo-controlled, double-blind, parallel study assessed the safety, tolerability, pharmacokinetics, and pharmacodynamics of exenatide once weekly (QW) in 30 Japanese patients with type 2 diabetes (T2D) suboptimally controlled by diet and exercise alone or combined with biguanide, sulfonylurea, thiazolidinedione, or combinations of these agents (58.6% male; 58+/-9 years; body mass index 26.3+/-2.9 kg/m(2); hemoglobin A(1c) [HbA(1c)] 7.4+/-0.8%; fasting plasma glucose [FPG] 156.1+/-29.1 mg/dL; duration of T2D 6+/-5 years; means +/- SD). Patients were randomized in a 1:1:1 ratio to subcutaneous placebo QW, exenatide QW 0.8 mg, or exenatide QW 2.0 mg for 10 weeks. All evaluable patients were analyzed (placebo QW, n=10; exenatide QW 0.8 mg, n=10; exenatide QW 2.0 mg, n=9), unless otherwise stated. Steady-state plasma exenatide concentrations were observed by Week 8 of the study. For the evaluable pharmacokinetic population, geometric mean (90% confidence interval) steady-state plasma concentrations (pg/mL) were 81.2 (68.3-96.4) and 344.5 (256.5-462.7) with exenatide QW 0.8 mg (n=8) and exenatide QW 2.0 mg (n=5), respectively. Baseline-to-Week 10 glycemic improvements with placebo QW, exenatide QW 0.8 mg, and exenatide QW 2.0 mg, respectively, were: HbA(1c) (%): -0.4+/-0.3, -1.0+/-0.7, and -1.5+/-0.7; FPG (mg/dL): -20.5+/-20.4, -25.2+/-10.9, and -50.8+/-27.8; and 2-hour postprandial plasma glucose excursions (mg/dL): -8.8+/-26.9, -50.0+/-41.1, and -59.7+/-26.8 (means +/- SD). No serious adverse events (AEs) were reported and no AEs led to study discontinuation in any group. The most frequent AE observed was mild-to-moderate injection site induration. No serious hypoglycemia was reported. Exenatide QW for 10 weeks was well tolerated and improved short-term glycemic control in Japanese patients with suboptimally controlled T2D.

Exenatide: incretin therapy for patients with Type 2 diabetes mellitus

Exenatide is the first in a novel class of drugs that mimics naturally occurring glucagon-like peptide 1. In patients with Type 2 diabetes mellitus (T2DM), control of both glycemia and bodyweight are important to minimize the risk of diabetes complications. Exenatide improves glycemic control through glucose-dependent insulin secretion, suppression of glucagon secretion, delaying gastric emptying and suppressing appetite. Exenatide therapy significantly reduced glycated hemoglobin (Hb_A1c) and fasting and postprandial plasma glucose when added to metformin and/or sulfonylureas, with an average weight loss of 2 kg. Furthermore, exenatide-treated patients sustained the reductions achieved in Hb_A1c at 12 weeks with a progressive reduction in bodyweight during 3-year follow-up. Exenatide is generally well tolerated; nausea is the most common side effect but significantly reduces over time and with gradual dose titration. Hypoglycemia at a rate greater than placebo only occurred in combination with sulfonylureas. Exenatide may enable patients with T2DM to improve glycemic control while reducing the risk of hypoglycemia and provoking weight loss.

Incretins: pathophysiological and therapeutic implications of glucose-dependent insulinotropic polypeptide and glucagon-like peptide-1

Incretins such as glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) are intestinal postprandial hormones that stimulate insulin release from the pancreas as long as circulating glucose concentrations are raised. In addition to their effect on insulin secretion and consequent glucose lowering, GIP and GLP-1, especially the latter, have a number of physiological effects such as inhibition of glucagon release, gastric emptying and food intake, as well as a tropic action on pancreatic B-cell mass. There is currently a pandemic of obesity and diabetes, and existing treatments are largely inadequate both in regard to efficacy as well as their ability to tackle important factors in the pathogenesis of type 2 diabetes (T2D). There is increasing evidence that current treatments do not address the issue of progressive B-cell failure in T2D. Since obesity is the engine that is driving the epidemic of diabetes, it is disappointing that most treatments that succeed in lowering plasma glucose are also associated with weight gain. It is now well established that intensively treated T2D has a better outcome than standard treatment. Consequently, achieving better control of diabetes with lower HbA1c is the goal of optimal treatment. Despite the use of usual therapeutic agents in T2D, often in high doses and as combinations, such as metformin, sulphonylurea, α-glycosidase inhibitors, thiazolidinediones and a number of animal and human insulin preparations, optimal control of glycaemia is not achieved. The use of incretins as therapeutic agents offers a new approach to the treatment of T2D.

Pharmacokinetics and pharmacodynamics of exenatide following alternate routes of administration

Exenatide is a 39-amino acid peptide incretin mimetic approved for adjunctive treatment of type 2 diabetes. It shares several glucoregulatory activities with the mammalian hormone, glucagon-like peptide-1 (GLP-1). In clinical use, subcutaneous exenatide injections demonstrate glucoregulatory and weight loss effects with sustained plasma concentrations in the 50-100 pM range. We investigated the pharmacokinetics of exenatide in normoglycemic rats and biological activity in diabetic db/db mice after delivery to various epithelial surfaces of the intestinal and respiratory tracts. In rats, elimination kinetics were similar for all routes of administration (median k(e) 0.017 min(-1)). Bioavailability (versus intravenous administration) and C(max) per unit dose differed markedly. For gastrointestinal administration, sublingual administration invoked the highest bioavailability (0.37%); in db/db mice, potentially therapeutic concentrations were obtainable. In contrast, intraduodenal bioavailability was low (0.0053%). In regard to respiratory surfaces, bioavailability of intratracheal exenatide was up to 13.6%, and for nasal administration, 1.68%. Both routes of administration produced therapeutic plasma concentrations and glucose-lowering in db/db mice. At high doses, aerosolized exenatide also achieved effective concentrations and glucose-lowering. In summary, the intestinal tract seems to have limited potential as a route of exenatide administration, with sublingual being most promising. In contrast, the respiratory tract appears to be more viable, comparing favorably with the clinically approved subcutaneous route. Despite little optimization of the delivery formulation, exenatide bioavailability compared favorable to that of several commercially available bioactive peptides.

Effects of once-weekly dosing of a long-acting release formulation of exenatide on glucose control and body weight in subjects with type 2 diabetes

OBJECTIVE

In patients with type 2 diabetes, exenatide reduces A1C, postprandial and fasting glucose, and weight. In this study we investigated the effects of continuous exenatide administration from a long-acting release (LAR) formulation.

RESEARCH DESIGN AND METHODS

In this randomized, placebo-controlled phase 2 study, exenatide LAR (0.8 or 2.0 mg) was administered subcutaneously once weekly for 15 weeks to subjects with type 2 diabetes (n = 45) suboptimally controlled with metformin (60%) and/or diet and exercise (40%): 40% female, A1C (mean +/- SD) 8.5 +/- 1.2%, fasting plasma glucose 9.9 +/- 2.3 mmol/l, weight 106 +/- 20 kg, and diabetes duration 5 +/- 4 years.

RESULTS

From baseline to week 15, exenatide LAR reduced mean +/- SE A1C by -1.4 +/- 0.3% (0.8 mg) and -1.7 +/- 0.3% (2.0 mg), compared with +0.4 +/- 0.3% with placebo LAR (P < 0.0001 for both). A1C of < or =7% was achieved by 36 and 86% of subjects receiving 0.8 and 2.0 mg exenatide LAR, respectively, compared with 0% of subjects receiving placebo LAR. Fasting plasma glucose was reduced by -2.4 +/- 0.9 mmol/l (0.8 mg) and -2.2 +/- 0.5 mmol/l (2.0 mg) compared with +1.0 +/- 0.7 mmol/l with placebo LAR (P < 0.001 for both). Exenatide LAR reduced self-monitored postprandial hyperglycemia. Subjects receiving 2.0 mg exenatide LAR had body weight reductions (-3.8 +/- 1.4 kg) (P < 0.05), whereas body weight was unchanged with both placebo LAR and the 0.8-mg dose. Mild nausea was the most frequent adverse event. No subjects treated with exenatide LAR withdrew from the study.

CONCLUSIONS

Exenatide LAR offers the potential of 24-h glycemic control and weight reduction with a novel once-weekly treatment for type 2 diabetes.

The role of alpha-cell dysregulation in fasting and postprandial hyperglycemia in type 2 diabetes and therapeutic implications

The hyperglycemic activity of pancreatic extracts was encountered some 80 yr ago during efforts to optimize methods for the purification of insulin. The hyperglycemic substance was named "glucagon," and it was subsequently determined that glucagon is a 29-amino acid peptide synthesized and released from pancreatic alpha-cells. This article begins with a brief overview of the discovery of glucagon and the contributions that somatostatin and a sensitive and selective assay for pancreatic (vs. gut) glucagon made to understanding the physiological and pathophysiological roles of glucagon. Studies utilizing these tools to establish the function of glucagon in normal nutrient homeostasis and to document a relative glucagon excess in type 2 diabetes mellitus (T2DM) and precursors thereof are then discussed. The evidence that glucagon excess contributes to the development and maintenance of fasting hyperglycemia and that failure to suppress glucagon secretion contributes to postprandial hyperglycemia is then reviewed. Although key human studies are emphasized, salient animal studies highlighting the importance of glucagon in normal and defective glucoregulation are also described. The past eight decades of research in this area have led to development of new therapeutic approaches to treating T2DM that have been shown to, or are expected to, improve glycemic control in patients with T2DM in part by improving alpha-cell function or by blocking glucagon action. Accordingly, this review ends with a discussion of the status and therapeutic potential of glucagon receptor antagonists, alpha-cell selective somatostatin agonists, glucagon-like peptide-1 agonists, and dipeptidyl peptidase-IV inhibitors. Our overall conclusions are that there is considerable evidence that relative hyperglucagonemia contributes to fasting and postprandial hyperglycemia in patients with T2DM, and there are several new and emerging pharmacotherapies that may improve glycemic control in part by ameliorating the hyperglycemic effects of this relative glucagon excess.

Exenatide in type 2 diabetes: treatment effects in clinical studies and animal study data

The therapeutic options for treating type 2 diabetes have been widened by the introduction of exenatide as the first incretin mimetic. Incretins are gut hormones that contribute to the stimulation of insulin secretion after a carbohydrate rich meal. The incretin hormone glucagon-like peptide-1 (GLP-1) not only stimulates insulin secretion under hyperglycaemic conditions, but also suppresses glucagon secretion, slows gastric emptying, induces satiety and improves beta cell function in type 2 diabetes. These beneficial effects have awakened the interest to use GLP-1 for the treatment of type 2 diabetes. Because of its short biological half-life, GLP-1 itself is not practical for type 2 diabetes therapy. Exenatide is a peptide found in the lizard Heloderma suspectum and has a high similarity to GLP-1. Exenatide belongs to the novel class of incretin mimetics because of its incretin-like action. It has a much longer biological half life than GLP-1 and is a GLP-1 receptor agonist that can be used for therapeutic purposes by twice daily injection. Clinical studies and clinical experience with exenatide have shown a significant reduction in HbA1c, fasting- and postprandial glucose and a marked reduction in body weight in type 2 diabetic patients. Animal studies reveal an improvement of beta cell function and an increase in beta cell mass after exenatide treatment. This review gives an overview on exenatide, its pharmacological profile and its role and potential in the therapeutic setting of type 2 diabetes. Furthermore, future developments concerning exenatide application are highlighted.

Diabetes mellitus in older men

Most persons with diabetes mellitus are over the age of 60 years. Males develop diabetes more commonly than females. Older diabetics tend to have both impaired insulin release as well as insulin resistance. In older persons diabetes mellitus is associated with decreased functional status and cognitive dysfunction. In general, older persons with diabetes are inclined to be underdiagnosed and undertreated. Managing diabetes in older persons requires special considerations because of their differences in pathophysiology of diabetes and strong association with functional, cognitive impairments and comorbidities. The use of strict therapeutic diets is not recommended in older persons. Treatment of hypertension and hyperglycemia can improve outcomes in older persons. The interdisciplinary team approach is important for care of older diabetic persons.