Vildagliptin, a dipeptidyl peptidase-IV inhibitor, improves model-assessed beta-cell function in patients with type 2 diabetes

Changes of dipeptidyl peptidase IV (DPP-IV) in obese children with weight loss: relationships to peptide YY, pancreatic peptide, and insulin sensitivity

AIM

Gastrointestinal (GI) hormones are involved in satiety regulation and in glucose metabolism. Most GI hormones are hydrolyzed and inactivated by the same enzyme, dipeptidyl peptidase IV (DPP-IV). We analyzed changes of DPP-IV after weight loss in obese children and its relationships to the GI hormones pancreatic peptide (PP), peptide YY (PYY), and insulin sensitivity.

METHODS

We measured at baseline and one year later anthropometrics, percentage body fat based on skinfold thickness, DPP-IV, PP, PYY, insulin, and glucose concentrations in 18 obese children (mean age 10.9 years, 44% male, mean BMI 28.5 kg/m2) who participated in a one-year lifestyle intervention program based on physical activity, nutrition course, and behavioral therapy. Insulin sensitivity was calculated using QUICKI.

RESULTS

Changes of DPP-IV correlated significantly to the changes of percentage body fat (r = 0.47) and BMI SDS (r = 0.60). In partial regression analysis adjusted for change in weight status, changes of DPP-IV correlated significantly to changes of PYY (r = -0.43), PP (r = -0.49), QUICKI (r = -0.53), and insulin (r = 0.57). The 10 children with substantial weight loss significantly reduced their DPP-IV and insulin concentrations, while QUICKI, PYY, and PP levels significantly increased. In children without substantial weight loss no significant changes were observed.

CONCLUSIONS

These findings suggest that the increase of fasting PP and PYY in weight loss is influenced at least in part by a decrease of their cleavage enzyme DPP-IV. Further research is necessary to evaluate the mechanisms in weight loss leading to a decrease of DPP-IV activity and consequently to an improvement of insulin sensitivity.

Prevention of beta-cell destruction in autoimmune diabetes: current approaches and future prospects

Type 1 diabetes (T1D) is an autoimmune disease resulting from the destruction of pancreatic beta-cells. The main aim of treatment should be to prevent beta-cell destruction and preserve existing beta-cells in individuals with progressive autoimmunity. This can be achieved in several ways and in this chapter the authors have reviewed recent approaches that are currently being tested in animal models and human T1D patients under the following categories: i) antigen based therapy, ii) antibody-based therapy iii) other forms of therapy and iv) failed therapies.

The effects of glucagon-like peptide-1 on the beta cell

Type 2 diabetes is a progressive disease characterized by insulin resistance and impaired beta-cell function. Treatments that prevent further beta-cell decline are therefore essential for the management of type 2 diabetes. Glucagon-like peptide-1 (GLP-1) is an incretin hormone that is known to stimulate glucose-dependent insulin secretion. Furthermore, GLP-1 appears to have multiple positive effects on beta cells. However, GLP-1 is rapidly degraded by dipeptidyl peptidase-4 (DPP-4), which limits the clinical relevance of GLP-1 for the treatment of type 2 diabetes. Two main classes of GLP-1-based therapies have now been developed: DPP-4 inhibitors and GLP-1 receptor agonists. Liraglutide and exenatide are examples of GLP-1 receptor agonists that have been developed to mimic the insulinotropic characteristics of endogenous GLP-1. Both have demonstrated improved beta-cell function in patients with type 2 diabetes, as assessed by homoeostasis model assessment-B analysis and proinsulin : insulin ratio. Additionally, liraglutide and exenatide are able to enhance first- and second-phase insulin secretion and are able to restore beta-cell sensitivity to glucose. Preclinical studies have shown that both liraglutide and exenatide treatment can increase beta-cell mass, stimulate beta-cell proliferation, increase beta-cell neogenesis and inhibit beta-cell apoptosis. Clinical studies are needed to confirm these findings in humans. Replication of these data in humans could have important clinical implications for the treatment of type 2 diabetes.

Optimizing outcomes with incretin-based therapies: practical information for nurse practitioners to share with patients

PURPOSE

To introduce the role of incretin therapies and suggest strategies for nurse practitioners to implement them in practice.

DATA SOURCES

PubMed, Medline, summary of product characteristics/package inserts.

CONCLUSIONS

Incretin-based therapies offer a new alternative to currently available agents. They provide adequate levels of glycemic control and are associated with low incidence of hypoglycemia and weight gain. Dipeptidyl peptidase-4 inhibitors, for example sitagliptin, have a modest effect on A1c levels (-0.7%) as monotherapy; however, they reduce A1c to a greater extent when combined with metformin ( approximately 2.0%). Typical starting dose of sitagliptin is 100 mg; dose adjustments are required in subjects with renal complications. Glucagon-like peptide-1 receptor agonists, exenatide and liraglutide, reduce A1c levels (often in excess of 1.5%) and body weight. Exenatide has a starting dose of 5 mug and is not recommended for patients with hepatic impairment or severe/end-stage renal disease. Liraglutide has been found to benefit from a stepwise dose escalation (i.e., 0.6 mg weekly increments) until a 1.8-mg dose is reached. Unlike exenatide, dose adjustments in patients with renal and hepatic complications are not required.

IMPLICATIONS FOR PRACTICE

Incretin-based therapies may help to overcome some of the drawbacks of current therapies used to treat type 2 diabetes.

Comparison of vildagliptin and thiazolidinedione as add-on therapy in patients inadequately controlled with metformin: results of the GALIANT trial--a primary care, type 2 diabetes study

AIM

To assess the efficacy and tolerability of vildagliptin compared with thiazolidinediones (TZDs) as an add on to metformin treatment in a primary care patient population with type 2 diabetes.

METHODS

This was a randomized, 12-week, open-label study comparing vildagliptin (100 mg, n = 1653) and TZD (agent and dose at the investigators' discretion, n = 825) add-on therapy in patients inadequately controlled [haemoglobin A(1C) (HbA(1c)): 7-10%] on a stable dose of metformin (> or =1000 mg/day). The primary objective was to test non-inferiority of vildagliptin to TZDs for the difference in change in HbA(1c) from baseline [established if the upper limit of the two-sided 95% confidence intervals (CI) did not exceed 0.4%].

RESULTS

Mean (+/- s.e.) change in HbA(1c) from baseline to study endpoint was -0.68 +/- 0.02% in the vildagliptin group and -0.57 +/- 0.03% in the TZD group. The difference between groups was -0.11% (95% CI: -0.17% and -0.04%), establishing the non-inferiority of vildagliptin (p = 0.001) after 3 months of treatment. Vildagliptin was non-inferior to TZDs for subgroups of race, age and body mass index. Body weight increased in the TZD group (0.33 +/- 0.11 kg) and decreased in the vildagliptin group (mean: -0.58 +/- 0.09 kg; p < 0.001 for difference). Adverse events occurred in similar proportions of patients in both groups (vildagliptin: 39.5% and TZD: 36.3%) Hypoglycaemia and abnormal changes in liver enzymes were uncommon.

CONCLUSIONS

This short-term study suggests that vildagliptin is as effective as TZDs after 3-month treatment as an add-on to metformin in a primary care population that included diverse patient subgroups.

Present and Prospective Pharmacotherapy for the Management of Patients with Type 2 Diabetes

Diabetes Mellitus is a chronic condition prevalent worldwide. Type 2 diabetes is the most common form of diabetes, comprising 90% to 95% of all cases. Over the last few decades, the importance of glycemic control and its impact on prevention of diabetes-related complications has been documented in multiple clinical trials. As most patients with type 2 diabetes will require pharmacologic intervention to achieve and maintain appropriate glycemic control, new medications targeting different aspects of the pathophysiology of type 2 diabetes have been a significant focus of research and development. During the last decade, multiple new medications for diabetes management have become available: these medications have novel mechanisms of action, differences in effectiveness, and varying side effect profiles which will be reviewed in this article. Some of these newer medications, such as the GLP-1 analogues and DPP-4 inhibitors, have become widely accepted as therapeutic options for the management of type 2 diabetes.Additional classes of glucose-lowering medications are expected to become available in the near future. This manuscript will summarize available data regarding these newer and prospective medications for the management of type 2 diabetes.

Clinical results of treating type 2 diabetic patients with sitagliptin, vildagliptin or saxagliptin--diabetes control and potential adverse events

Inhibition of dipeptidyl peptidase-4 (DPP-4) is a novel oral treatment for type 2 diabetes. DPP-4 inhibition increases insulin secretion and reduces glucagon secretion by preventing the inactivation of glucagon-like peptide-1 (GLP-1), thereby lowering glucose levels. Several DPP-4 inhibitors are in clinical development; more studies exist for sitagliptin and vildagliptin. They improve metabolic control in type 2 diabetes in monotherapy and also in combination with metformin, sulphonylurea and thiazolidinediones. HbA(1c) is reduced by approximately 0.6-1.1% in studies up to 52 weeks. Similar, although more limited, results were obtained for saxagliptin. DPP-4 inhibitors are safe and tolerable with no increased risk of adverse events compared to placebo and have a low risk of hypoglycaemia. DPP-4 inhibitors are body weight-neutral. The DPP-4 inhibitors are recommended for use in the early stage of type 2 diabetes, in combination with metformin in subjects with inadequate glycaemic control. DPP-4 inhibition may also be used in combination with sulphonylurea and thiazolidinediones and potentially also in combination with insulin. The durability and long-term safety of DPP-4 inhibitors remain to be established.

Comparison of vildagliptin and metformin monotherapy in elderly patients with type 2 diabetes: a 24-week, double-blind, randomized trial

AIMS

The study evaluated the efficacy and tolerability of the dipeptidyl peptidase-4 inhibitor, vildagliptin, and metformin in drug-naïve elderly patients with type 2 diabetes. The primary objective was to demonstrate non-inferiority of vildagliptin vs. metformin in glycated haemoglobin (HbA1c) reduction.

METHODS

This was a double-blind, randomized, multicentre, active-controlled, parallel-group study of 24-week treatment with vildagliptin (100 mg daily, n=169) or metformin (titrated to 1500 mg daily, n=166) in drug-naïve patients with type 2 diabetes aged>or=65 years (baseline HbA1c 7-9%).

RESULTS

Participants had a mean age of 71 years, known duration of diabetes of 3 years and mean baseline HbA1c of 7.7%. At end-point, vildagliptin was as effective as metformin, improving HbA1c by -0.64+/-0.07% and -0.75+/-0.07%, respectively, meeting the predefined statistical criterion for non-inferiority (upper limit of 95% confidence interval for between-treatment difference<or=0.3%). Body weight changes were -0.45+/-0.20 kg in vildagliptin-treated patients (p=0.02) and -1.25+/-0.19 kg in metformin-treated patients (p<0.001; p=0.004 vs. vildagliptin). The proportion of patients experiencing an adverse event (AE) was 44.3 vs. 50.3% in patients receiving vildagliptin and metformin respectively. Gastrointestinal (GI) AEs were significantly more frequent with metformin (24.8%) than with vildagliptin (15.0%, p=0.028), mainly driven by a 4.4-fold higher incidence of diarrhoea. A low incidence of hypoglycaemia was observed in both treatment groups (0% with vildagliptin and 1.2% with metformin).

CONCLUSIONS

Vildagliptin is an effective and well-tolerated treatment option in elderly patients with type 2 diabetes, demonstrating similar improvement in glycaemic control as metformin, with superior GI tolerability.

Pharmacokinetics, pharmacodynamics and tolerability of multiple oral doses of linagliptin, a dipeptidyl peptidase-4 inhibitor in male type 2 diabetes patients

AIMS

To investigate the safety, tolerability, pharmacokinetic and pharmacodynamic properties of multiple oral doses of the dipeptidyl peptidase-4 (DPP-4) inhibitor linagliptin (BI 1356) in patients with type 2 diabetes mellitus.

METHODS

Forty-seven male type 2 diabetic patients received linagliptin 1, 2.5, 5 or 10 mg, or placebo, once daily for 12 days.

RESULTS

Linagliptin exposure [area under the plasma concentration-time curve and maximum plasma concentration (Cmax)] increased less than proportionally with dose. Accumulation half-life was short (8.6-23.9 h), resulting in rapid attainment of steady state (2-5 days) and little accumulation (range: 1.18-2.03). The long terminal half-life (113-131 h) led to a sustained inhibition of DPP-4 activity. Renal excretion was below 1% on day 1 in all dose groups. Inhibition of plasma DPP-4 activity correlated well with linagliptin plasma concentrations, resulting in DPP-4 inhibition >90% in the two highest dose groups; even 24 h postdose, DPP-4 inhibition was >80%. Following an oral glucose tolerance test, 24 h after the last dose, statistically significant reductions of glucose excursions were observed with linagliptin (2.5, 5 and 10 mg doses) compared with placebo. Linagliptin was well tolerated. The frequency of adverse events (AEs) was not higher with linagliptin (54%) than with placebo (75%). No serious AEs and no episodes of hypoglycaemia were reported.

CONCLUSIONS

In type 2 diabetic patients, multiple rising doses of linagliptin were well tolerated and resulted in significant improvements of glucose parameters. Together with the favourable pharmacokinetics, these results confirm the unique profile of linagliptin in the DPP-4 inhibitor class.

Dipeptidyl peptidase-IV inhibitor use associated with increased risk of ACE inhibitor-associated angioedema

Dipeptidyl peptidase-IV (DPP-IV) inhibitors decrease degradation of the incretins. DPP-IV inhibitors also decrease degradation of peptides, such as substance P, that may be involved in the pathogenesis of angiotensin-converting enzyme (ACE) inhibitor-associated angioedema. This study tested the hypothesis that DPP-IV inhibition affects risk of clinical angioedema, by comparing the incidence of angioedema in patients treated with the DPP-IV inhibitor vildagliptin versus those treated with comparator in Phase III randomized clinical trials. Prospectively defined angioedema-related events were adjudicated in a blinded fashion by an internal medicine adjudication committee and expert reviewer. Concurrent ACE inhibitor or angiotensin receptor blocker exposure was ascertained from case report forms. Study drug exposure was ascertained from unblinded data from phase III studies. Odds ratios and 95% confidence intervals comparing angioedema risk in vildagliptin-treated and comparator-treated patients were calculated for the overall population and for patients taking ACE inhibitors or angiotensin receptor blockers, using both an analysis of pooled data and a meta-analysis (Peto method). Overall, there was no association between vildagliptin use and angioedema. Among individuals taking an ACE inhibitor, however, vildagliptin use was associated with an increased risk of angioedema (14 confirmed cases among 2754 vildagliptin users versus 1 case among 1819 comparator users: odds ratio 4.57 [95% confidence interval 1.57 to 13.28]) in the meta-analysis. Vildagliptin use may be associated with increased risk of angioedema among patients taking ACE inhibitors, although absolute risk is small. Physicians confronted with angioedema in a patient taking an ACE inhibitor and DPP-IV inhibitor should consider this possible drug-drug interaction.

Incretin therapies: effects beyond glycemic control

Impaired insulin secretion plays a major role in the pathogenesis of type 2 diabetes mellitus, and progressive loss of beta-cell function is a pathophysiologic hallmark of type 2 diabetes. Recent science has elaborated on the role of the incretin hormones on beta-cell function and insulin secretion, as well as the role that incretin-based pharmacotherapies may have on glycemic control and beta-cell function, possibly altering the progressive loss of beta-cell function and possibly reversing/halting disease progression. However, incretin-based therapies may also have benefits extending beyond glycemic control and insulin secretion. In this review we examine some of those "beyond-glycemic" benefits, including presentation of data on weight reduction, blood pressure lowering, beneficial changes in the lipid profile, and improvements in myocardial and endothelial function. We investigate how those effects may help ameliorate the cardiovascular burden in patients with diabetes.

Incretin therapies: effects beyond glycemic control

Impaired insulin secretion plays a major role in the pathogenesis of type 2 diabetes mellitus, and progressive loss of beta-cell function is a pathophysiologic hallmark of type 2 diabetes. Recent science has elaborated on the role of the incretin hormones on beta-cell function and insulin secretion, as well as the role that incretin-based pharmacotherapies may have on glycemic control and beta-cell function, possibly altering the progressive loss of beta-cell function and possibly reversing/halting disease progression. However, incretin-based therapies may also have benefits extending beyond glycemic control and insulin secretion. In this review we examine some of those "beyond-glycemic" benefits, including presentation of data on weight reduction, blood pressure lowering, beneficial changes in the lipid profile, and improvements in myocardial and endothelial function. We investigate how those effects may help ameliorate the cardiovascular burden in patients with diabetes.

Incretin-based therapies: new treatments for type 2 diabetes in the new millennium

The advent of 'incretin-based therapies' - GLP-1 agonists and dipeptidyl-peptidase-4 inhibitors - which result in improvements in glycemic control comparable to those with existing oral hypoglycemic agents, and potentially improve cardiovascular and pancreatic beta-cell function, represents a major therapeutic advance in the management of type 2 diabetes. Gastrointestinal adverse effects occur commonly with GLP-1 agonists, and rarely with DPP-4 inhibitors, but are dose-dependent and usually transient. The low risk of hypoglycemia, and beneficial or neutral effects on body weight, render GLP-1 agonists and DPP-4 inhibitors suitable alternatives to insulin secretagogues and insulin in overweight and elderly patients. Incretin-based therapies also improve quality of life in patients with type 2 diabetes, and may be cost-effective in the long term.

Long-term 2-year safety and efficacy of vildagliptin compared with rosiglitazone in drug-naïve patients with type 2 diabetes mellitus

AIMS

To assess the long-term safety and the sustained glycaemic control of vildagliptin compared with rosiglitazone over 2-year treatment in drug-naïve type 2 diabetes mellitus patients.

METHODS

This was an additional 80-week, multicentre, double-blind and active-controlled extension to a 24-week core study comparing the treatments of vildagliptin (50 mg b.i.d., n = 396) to rosiglitazone (8 mg q.d., n = 202). The primary efficacy variable was the mean change in haemoglobin A1c (HbA1c) from the core study baseline (day 1) to the end of 104 weeks (the extension endpoint).

RESULTS

Vildagliptin and rosiglitazone showed statistically significant and sustained HbA1c reductions from a core mean baseline of 8.6 and 8.7% to 7.8 and 7.3% respectively (both significant, p < 0.001). However, rosiglitazone-treated patients showed significantly greater mean HbA1c reductions (mean difference 0.62%, s.e. 0.13, p < 0.001) compared with vildagliptin. The overall lipid profile significantly improved with vildagliptin compared to rosiglitazone treatment. Body weight remained unchanged in vildagliptin-treated patients despite improvements in glycaemic control but significantly increased (mean change from core study baseline 4.67 kg) in rosiglitazone-treated patients (p < 0.001). Notably, a lower incidence of peripheral oedema was seen with vildagliptin (4.6%) compared with rosiglitazone treatment (11.1%). More serious adverse events (SAEs) occurred in vildagliptin- than rosiglitazone-treated patients (12.5 and 9.1% respectively), but only one SAE each in both treatment group was suspected to be related to study drug. Three non-study drug-related deaths (vildagliptin: 2 and rosiglitazone: 1) were reported. Four mild hypoglycaemic events were observed with vildagliptin.

CONCLUSIONS

This study showed that the similar short-term HbA1c reductions seen with both vildagliptin and rosiglitazone treatments were more durable after 104 weeks of treatment with rosiglitazone than vildagliptin. However, this greater durability with rosiglitazone was at the expense of weight gain (almost 5 kg), higher incidences of peripheral oedema and a less favourable plasma lipid profile compared with vildagliptin.

The backbone of oral glucose-lowering therapy: time for a paradigm shift?

The complex array of metabolic abnormalities associated with type 2 diabetes provides a number of new targets for therapeutic intervention. Although the established oral glucose-lowering therapies, metformin and the sulfonylureas, continue to provide the backbone of therapeutic approaches, the thiazolidinediones (TZDs) also play an important role. Further, a new class of oral agents, the dipeptidyl peptidase-IV (DPP-IV) inhibitors, has recently become available with apparent utility in decreasing postprandial glucose excursions. This review examines how the TZDs and the DPP-IV inhibitors might integrate into current treatment strategies, considering not only glycemic goals, but also longer-term benefits such as durability of glycemic control, effect on metabolic parameters and cardiovascular outcomes. A practical approach is taken, reflecting potential clinical situations in which therapeutic intervention is required.

Study of the pharmacokinetic interaction of vildagliptin and metformin in patients with type 2 diabetes

OBJECTIVE

Metformin is widely used for treating patients with type 2 diabetes, often as first-line therapy; however, many patients with type 2 diabetes are unable to maintain adequate glycemic control with metformin alone. Vildagliptin, an orally active, potent and selective dipeptidyl peptidase IV (DPP-4) inhibitor, may represent an appropriate antihyperglycemic agent for combination with metformin to improve glycemic control in such patients. This study assessed the effects of coadministration of vildagliptin and metformin on the steady-state pharmacokinetics of each drug.

RESEARCH DESIGN AND METHODS

In this open-label, single-center, randomized, three-period, three-treatment crossover study, 17 patients with type 2 diabetes received vildagliptin 100 mg once daily; metformin 1000 mg once daily; or vildagliptin 100 mg once daily plus metformin 1000 mg once daily. Blood samples for pharmacokinetic sampling were taken frequently on the final day (Day 5) of each treatment period. Lack of pharmacokinetic interaction was defined as the ratio of geometric mean (GMR) and 90% confidence interval (CI) for combination:monotherapy being within the range 0.80-1.25.

RESULTS

Coadministration with metformin had no effect on vildagliptin AUC(0-24) (GMR, 0.94; 90% CI 0.90, 0.99) although there was an 18% decrease in vildagliptin C(max) (GMR 0.82; 90% CI 0.73, 0.91). Coadministration with vildagliptin had no effect on metformin C(max) (GMR 1.04; 90% CI 0.94, 1.16). but caused a 15% increase in AUC(0-24) (GMR 1.15; 90% CI 1.06, 1.25). Both monotherapies and combination therapy were well tolerated. Seven patients reported a total of 10 adverse events; none was serious.

CONCLUSIONS

Coadministration of vildagliptin and metformin had a small effect on the pharmacokinetics of each drug in patients with type 2 diabetes; however, this is not likely to be clinically relevant. This small, open-label trial suggests that vildagliptin could be coadministered with metformin without any dose adjustment for either agent.

Vildagliptin: a new oral treatment for type 2 diabetes mellitus

Vildagliptin is a new oral antidiabetic agent that enhances pancreatic islet cell responsiveness to glucose. An extensive clinical program involving approximately 22,000 patients and 7000 patient-years of exposure to vildagliptin has shown that the agent is well tolerated and efficacious in improving glycemic control in patients with type 2 diabetes mellitus (T2DM). Monotherapy trials have shown that significant HbA1c lowering is accompanied by body weight-neutral and lipid-neutral effects, low risk of edema, and low risk of hypoglycemia. These characteristics make vildagliptin a favorable partner for combination therapy. Studies of vildagliptin as an add-on to metformin have shown significant improvements in glycemic control (comparable to that of thiazolidinedione add-on), with the combination being well tolerated and associated with low risks for hypoglycemia and adverse effects on weight or lipid levels. Good tolerability and clinically relevant improvements in glycemic control have also been observed with vildagliptin as an add-on treatment to sulfonylurea, thiazolidinedione, or insulin treatment or in initial combination treatment with pioglitazone. Improved beta-cell function and glycemic control have been shown with vildagliptin in subjects with impaired glucose tolerance and in T2DM patients with mild hyperglycemia, with some evidence in the latter suggesting the potential for modifying disease course.

Vildagliptin enhances islet responsiveness to both hyper- and hypoglycemia in patients with type 2 diabetes

CONTEXT

Dipeptidyl peptidase-4 inhibitors act by increasing plasma levels of glucagon-like peptide-1 and suppressing excessive glucagon secretion in patients with type 2 diabetes. However, their effects on the glucagon response to hypoglycemia are not established.

OBJECTIVE

The aim of the study was to assess effects of the dipeptidyl peptidase-4 inhibitor vildagliptin on alpha-cell response to hyper- and hypoglycemia.

DESIGN

We conducted a single-center, randomized, double-blind, placebo-controlled, two-period crossover study of 28-d treatment, with a 4-wk between-period washout.

PATIENTS

We studied drug-naive patients with type 2 diabetes and baseline glycosylated hemoglobin of 7.5% or less.

INTERVENTION

Participants received vildagliptin (100 mg/d) or placebo as outpatients. PRIMARY OUTCOME MEASURE(S): We measured the following: 1) change in plasma glucagon levels during hypoglycemic (2.5 mm glucose) clamp; and 2) incremental (Delta) glucagon area under the concentration-time curve from time 0 to 60 min (AUC(0-60 min)) during standard meal test. Before the study, it was hypothesized that vildagliptin would suppress glucagon secretion during meal tests and enhance the glucagon response to hypoglycemia.

RESULTS

The mean change in glucagon during hypoglycemic clamp was 46.7 +/- 6.9 ng/liter with vildagliptin treatment and 33.9 +/- 6.7 ng/liter with placebo; the between-treatment difference was 12.8 +/- 7.0 ng/liter (P = 0.039), representing a 38% increase with vildagliptin. In contrast, the mean glucagon DeltaAUC(0-60 min) during meal test with vildagliptin was 512 +/- 163 ng/liter x min vs. 861 +/- 130 ng/liter x min with placebo; the between-treatment difference was -349 +/- 158 ng/liter x min (P = 0.019), representing a 41% decrease with vildagliptin.

CONCLUSIONS

Vildagliptin enhances alpha-cell responsiveness to both the suppressive effects of hyperglycemia and the stimulatory effects of hypoglycemia. These effects likely contribute to the efficacy of vildagliptin to improve glycemic control as well as to its low hypoglycemic potential.

Effects of vildagliptin twice daily vs. sitagliptin once daily on 24-hour acute glucose fluctuations

There is increasing evidence that glycemic disorders such as rapid glucose fluctuations over a daily period might play an important role on diabetic complications. We evaluated the efficacy of sitagliptin 100 mg once daily vs. vildagliptin 50 mg twice daily on daily blood glucose fluctuations in patients with type 2 diabetes that was inadequately controlled by metformin. Forty-eight-hour continuous subcutaneous glucose monitoring (CSGM) was performed in patients treated with metformin plus vildagliptin (n=18) or sitagliptin (n=20) over a period of 3 months. The mean amplitude of glycemic excursions (MAGE) was used for assessing glucose fluctuations during the day. During a standardized meal, glucagon-like peptide-1 (GLP-1), glucagon, and insulin were measured. CSGM shows large MAGE decrements in the vildagliptin group compared with the sitagliptin group (P<.01). A marked increase in GLP-1 occurred during interprandial period in vildagliptin bid-treated toward sitagliptin 100 mg once daily (P<.01). Glucagon was more suppressed during interprandial period in subjects receiving vildagliptin compared to those receiving sitagliptin (P<.01). Since MAGE is associated with an activation of oxidative stress, our data suggest that dipeptidyl peptidase IV inhibition therapy should target not only reducing HbA(1c) but also flattening acute glucose fluctuations over a daily period.

New treatments in type 2 diabetes: a focus on the incretin-based therapies

The demonstration that the incretin hormone glucagon-like peptide 1 can improve glycaemic control in patients with type 2 diabetes has led to the rapid development during the last decade of promising new classes of agent for the management of type 2 diabetes. These agents possess a range of physiological effects that are associated with improved glycaemic control in diabetes including stimulation of glucose-dependent insulin secretion, suppression of glucagon secretion, slowing of gastric emptying, and reduction of food intake. In addition, preclinical studies suggest that incretin-based therapies may improve beta-cell function via enhancement of beta-cell mass and induction of genes important for differentiated beta-cell function. Exenatide, and the dipeptidyl peptidase-4 inhibitors, sitagliptin and vildagliptin are already approved, and liraglutide is currently completing Phase 3 trials. As these agents and standard oral therapies for type 2 diabetes lower glucose levels through different, but potentially complementary mechanisms, their use in combination should provide effective, potentially additive, glycaemic control. The incretin-based therapies also offer other advantages such as weight loss with exenatide and liraglutide, a reduced risk of hypoglycaemia, and as suggested by preclinical studies, a potential beta-cell preserving effect. Long-term outcome and safety data are not available for these agents, but they appear generally well-tolerated in comparison with existing therapies for type 2 diabetes. The multiple underlying glucose-lowering actions of the incretin-based therapies, as well as a lack of weight gain or even weight loss, make these important new additions to available antidiabetic agents expanding the treatment options available for patients.

Emerging dipeptidyl peptidase-4 inhibitors for the treatment of diabetes

Inhibition of dipeptidyl peptidase-4 (DPP-4) prevents the inactivation of glucagon-like peptide-1 (GLP-1). This increases circulating levels of active GLP-1, stimulates insulin secretion and inhibits glucagon secretion, resulting in lowering of glucose levels and improvement of glycemic control in patients with type 2 diabetes. Several DPP-4 inhibitors are emerging for therapeutic use. Most experience exists for sitagliptin, vildagliptin, saxagliptin and alogliptin. They all improve metabolic control in type 2 diabetes in monotherapy and in combination therapy with metformin, sulfonylurea and thiazolidinediones. Vildagliptin and alogliptin have also been shown to improve glycemic control when added to insulin therapy, and sitagliptin improves glycemic control in triple therapy with metformin plus thiazolidinedione. DPP-4 inhibition also shows a favorable safety profile, high tolerability, only a minimal risk of hypoglycemia, and body-weight neutrality. The main clinical indication for DPP-4 inhibitors will be in the early stage of type 2 diabetes, in combination with metformin or other treatments in subjects with inadequate glycemic control on these treatments alone. The durability and long-term safety of DPP-4 inhibition, as well as clinical positioning in relation to GLP-1 mimetics, remain now to be established.

Importance of postprandial glucose levels as a target for glycemic control in type 2 diabetes

Increasing evidence supports the importance of postprandial glucose (PPG) in glycemic control with regard to the development of complications in patients with diabetes. PPG plays a critical role in determining overall glycemic control, particularly in patients who are close to their glycemic goals. Data also indicate that postprandial hyperglycemia may have a greater effect on the development of cardiovascular complications compared with elevated fasting plasma glucose. Several antidiabetic agents that specifically target PPG are currently available, including glinides, glucagon-like peptide-1 mimetics, dipeptidyl peptidase-4 inhibitors, and rapid-acting insulin analogs. A more intensive approach to managing PPG may improve the care of patients with diabetes and, ultimately, the outcome of these patients.

Fifty-two-week efficacy and safety of vildagliptin vs. glimepiride in patients with type 2 diabetes mellitus inadequately controlled on metformin monotherapy

AIM

To examine the efficacy and safety of vildagliptin vs. glimepiride as add-on therapy to metformin in patients with type 2 diabetes mellitus in a 52-week interim analysis of a large, randomized, double-blind, multicentre study. The primary objective was to demonstrate non-inferiority of vildagliptin vs. glimepiride in glycosylated haemoglobin (HbA(1c)) reduction at week 52.

METHODS

Patients inadequately controlled on metformin monotherapy (HbA(1c) 6.5-8.5%) and receiving a stable dose of metformin (mean dose 1898 mg/day; mean duration of use 36 months) were randomized 1:1 to receive vildagliptin (50 mg twice daily, n = 1396) or glimepiride (titrated up to 6 mg/day; mean dose 4.5 mg/day, n = 1393).

RESULTS

Non-inferiority of vildagliptin was demonstrated (97.5% confidence interval 0.02%, 0.16%) with a mean (SE) change from baseline HbA(1c) (7.3% in both groups) to week 52 endpoint of -0.44% (0.02%) with vildagliptin and -0.53% (0.02%) with glimepiride. Although a similar proportion of patients reached a target HbA(1c) level of <7% with vildagliptin and glimepiride (54.1 and 55.5%, respectively), a greater proportion of patients reached this target without hypoglycaemia in the vildagliptin group (50.9 vs. 44.3%; p < 0.01). Fasting plasma glucose (FPG) reductions were comparable between groups (mean [SE] -1.01 [0.06] mmol/l and -1.14 [0.06] mmol/l respectively). Vildagliptin significantly reduced body weight relative to glimepiride (mean [SE] change from baseline -0.23 [0.11] kg; between-group difference -1.79 kg; p < 0.001) and resulted in a 10-fold lower incidence of hypoglycaemia than glimepiride (1.7 vs. 16.2% of patients presenting at least one hypoglycaemic event; 39 vs. 554 hypoglycaemic events, p < 0.01). No severe hypoglycaemia occurred with vildagliptin compared with 10 episodes with glimepiride (p < 0.01), and no patient in the vildagliptin group discontinued because of hypoglycaemia compared with 11 patients in the glimepiride group. The incidence of adverse events (AEs), serious AEs and adjudicated cardiovascular events was 74.5, 7.1 and 0.9%, respectively, in patients receiving vildagliptin, and 81.1, 9.5 and 1.6%, respectively, in patients receiving glimepiride.

CONCLUSIONS

When metformin alone fails to maintain sufficient glycaemic control, the addition of vildagliptin provides comparable efficacy to that of glimepiride after 52 weeks and displays a favourable AE profile, with no weight gain and a significant reduction in hypoglycaemia compared with glimepiride.

Drug evaluation: vildagliptin-metformin single-tablet combination

The single-tablet combination of vildagliptin and metformin addresses key defects of type 2 diabetes for improved glycemic control. By inhibiting the dipeptidyl peptidase-4 (DPP-4) enzyme, vildagliptin raises the levels of the active incretin hormones, glucagon-like peptide 1 and glucose-dependent insulinotropic peptide. This leads to increased synthesis and release of insulin from the pancreatic beta cells and decreased release of glucagon from the pancreatic alpha cells. The combination tablet also contains metformin, which addresses insulin resistance. The complementary mechanisms of action of the two agents in combination have been shown to provide additive and sustained reductions in hemoglobin A(1c) compared with metformin monotherapy. In active-controlled trials, the vildagliptin-metformin combination has been shown to produce equivalent reductions in hemoglobin A(1c) to pioglitazone-metformin and glimepiride-metformin combinations, without significant risk of hypoglycemia and without causing weight gain. In clinical trials, the overall incidence of any adverse event was similar in patients randomized to vildagliptin plus metformin and placebo plus metformin. Available data support the use of vildagliptin in combination with metformin as a promising second-line treatment for the management of type 2 diabetes and this is reflected in the latest UK National Institute for Health and Clinical Excellence draft guideline for consultation on new agents for blood glucose control in type 2 diabetes.

Inhibition of dipeptidyl peptidase-4 by vildagliptin during glucagon-like Peptide 1 infusion increases liver glucose uptake in the conscious dog

OBJECTIVE

This study investigated the acute effects of treatment with vildagliptin on dipeptidyl peptidase-4 (DPP-4) activity, glucagon-like peptide 1 (GLP-1) concentration, pancreatic hormone levels, and glucose metabolism. The primary aims were to determine the effects of DPP-4 inhibition on GLP-1 clearance and on hepatic glucose uptake.

RESEARCH DESIGN AND METHODS

Fasted conscious dogs were studied in the presence (n = 6) or absence (control, n = 6) of oral vildagliptin (1 mg/kg). In both groups, GLP-1 was infused into the portal vein (1 pmol . kg(-1) . min(-1)) for 240 min. During the same time, glucose was delivered into the portal vein at 4 mg . kg(-1) . min(-1) and into a peripheral vein at a variable rate to maintain the arterial plasma glucose level at 160 mg/dl.

RESULTS

Vildagliptin fully inhibited DPP-4 over the 4-h experimental period. GLP-1 concentrations were increased in the vildagliptin-treated group (50 +/- 3 vs. 85 +/- 7 pmol/l in the portal vein in control and vildagliptin-treated dogs, respectively; P < 0.05) as a result of a 40% decrease in GLP-1 clearance (38 +/- 5 and 22 +/- 2 ml . kg(-1) . min(-1), respectively; P < 0.05). Although hepatic insulin and glucagon levels were not significantly altered, there was a tendency for plasma insulin to be greater (hepatic levels were 73 +/- 10 vs. 88 +/- 15 microU/ml, respectively). During vildagliptin treatment, net hepatic glucose uptake was threefold greater than in the control group. This effect was greater than that predicted by the change in insulin.

CONCLUSIONS

Vildagliptin fully inhibited DPP-4 activity, reduced GLP-1 clearance by 40%, and increased hepatic glucose disposal by means beyond the effects of GLP-1 on insulin and glucagon secretion.

Dipeptidyl peptidase-4 inhibition by vildagliptin and the effect on insulin secretion and action in response to meal ingestion in type 2 diabetes

OBJECTIVE

The purpose of this study was to determine the mechanism by which dipeptidyl peptidase-4 inhibitors lower postprandial glucose concentrations.

RESEARCH DESIGN AND METHODS

We measured insulin secretion and action as well as glucose effectiveness in 14 subjects with type 2 diabetes who received vildagliptin (50 mg b.i.d.) or placebo for 10 days in random order separated by a 3-week washout. On day 9 of each period, subjects ate a mixed meal. Insulin sensitivity (S(I)), glucose effectiveness, and beta-cell responsivity indexes were estimated using the oral glucose and C-peptide minimal models. At 300 min 0.02 unit/kg insulin was administered intravenously.

RESULTS

Vildagliptin reduced postprandial glucose concentrations (905 +/- 94 vs. 1,008 +/- 104 mmol/6 h, P = 0.02). Vildagliptin did not alter net S(I) (7.71 +/- 1.28 vs. 6.41 +/- 0.84 10(-4) dl x kg(-1) x min(-1) x muU(-1) x ml(-1), P = 0.13) or glucose effectiveness (0.019 +/- 0.002 vs. 0.018 +/- 0.002 dl x kg(-1) x min(-1), P = 0.65). However, the net beta-cell responsivity index was increased (35.7 +/- 5.2 vs. 28.9 +/- 5.2 10(-9) min(-1), P = 0.03) as was total disposition index (381 +/- 48 vs. 261 +/- 35 10(-14) dl x kg(-1) x min(-2) x pmol(-1) x l(-1), P = 0.006). Vildagliptin lowered postprandial glucagon concentrations (27.0 +/- 1.1 vs. 29.7 +/- 1.5 microg x l(-1) x 6 h(-1), P = 0.03), especially after administration of exogenous insulin (81.5 +/- 6.4 vs. 99.3 +/- 5.6 ng/l, P = 0.02).

CONCLUSIONS

Vildagliptin lowers postprandial glucose concentrations by stimulating insulin secretion and suppressing glucagon secretion but not by altered insulin action or glucose effectiveness. A novel observation is that vildagliptin alters alpha-cell responsiveness to insulin administration, but the significance of this action is as yet unclear.

Treatment with the dipeptidyl peptidase-4 inhibitor vildagliptin improves fasting islet-cell function in subjects with type 2 diabetes

CONTEXT

Dipeptidyl peptidase 4 (DPP-4) inhibitors are proposed to lower blood glucose in type 2 diabetes mellitus (T2DM) by prolonging the activity of the circulating incretins, glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide 1 (GLP-1). Consistent with this mechanism of action, DPP-4 inhibitors improve glucose tolerance after meals by increasing insulin and reducing glucagon levels in the plasma. However, DPP-4 inhibitors also reduce fasting blood glucose, an unexpected effect because circulating levels of active GIP and GLP-1 are low in the postabsorptive state.

OBJECTIVE

The objective of the study was to examine the effects of DPP-4 inhibition on fasting islet function.

DESIGN

We conducted a randomized, double-blind, placebo-controlled trial.

SETTING

The study was performed in General Clinical Research Centers at two University Hospitals.

SUBJECTS

Forty-one subjects with T2DM were treated with metformin or diet, having good glycemic control with glycosylated hemoglobin values of 6.2-7.5%.

INTERVENTION

Subjects were treated with vildagliptin (50 mg twice daily) or placebo for 3 months, followed by a 2-wk washout. Major Outcome Measure: We measured insulin secretion in response to iv glucose and arginine before and after treatment and after drug washout.

RESULTS

There were small and comparable reductions in glycosylated hemoglobin in both groups over 3 months. Vildagliptin increased fasting GLP-1 levels in subjects taking metformin, but not those managed with diet, and raised active GIP levels slightly. DPP-4 inhibitor treatment improved the acute insulin and C-peptide responses to glucose (50 and 100% respectively; P < 0.05) and increased the slope of the C-peptide response to glucose (33%; P = 0.023).

CONCLUSION

Vildagliptin improves islet function in T2DM under fasting conditions. This suggests that DPP-4 inhibition has metabolic benefits in addition to enhancing meal-induced GLP-1 and GIP activity.

Beta-cell function assessment from modelling of oral tests: an effective approach

The quantitative study of beta-cell function has relied on mathematical models for almost 40 years. During the last decades, the initial elaborate models have been simplified with the aim of obtaining mathematical methods suitable for the assessment of beta-cell function in an individual from an intravenous test. In more recent times, modelling methods have been proposed for analysing oral glucose tolerance tests or meal tests. In this review, we describe these methods with particular emphasis on an approach we have developed. We discuss the relevance of potentiation of insulin secretion in an oral glucose test, which our model has reintroduced after the historical models. We provide evidence on the validity of the method and illustrate significant applications. We emphasize the importance of quantifying beta-cell function through multiple indices and highlight how our approach has provided new insight on the relationships between beta-cell function and insulin sensitivity and on the role of beta-cell function in glucose intolerance and diabetes.

An examination of beta-cell function measures and their potential use for estimating beta-cell mass

A characteristic and dominant feature of type 2 diabetes is a reduction in beta-cell function that is associated with a decrease in beta-cell volume. A decline in the first-phase insulin response following intravenous glucose administration can be demonstrated as the fasting glucose concentration increases. This response is completely absent before the glucose threshold that defines diabetes has been reached and at a time when beta-cells are clearly still present, implying that a functional beta-cell lesion has to exist independent of beta-cell loss. Surgical or chemical reductions of up to 65% of beta-cell volume demonstrate that functional adaptation of the normal beta-cell prevents a rise in fasting glucose or reduction in first-phase insulin response. However, the ability of glucose to potentiate the beta-cell's response to non-glucose secretagogues is reduced and is more closely associated with the reduction in beta-cell volume. The future, in terms of prevention and treatment of type 2 diabetes, lies in the ability to prevent and revert both beta-cell loss and dysfunction. However, until beta-cell volume can be quantified reliably and non-invasively, we will need to rely on the ability of glucose to potentiate insulin release as the best surrogate estimate of the number of beta-cells.

Evidence that vildagliptin attenuates deterioration of glycaemic control during 2-year treatment of patients with type 2 diabetes and mild hyperglycaemia

AIM

To assess the 2-year efficacy and tolerability of vildagliptin (50 mg once daily) in patients with type 2 diabetes (T2DM) and mild hyperglycaemia.

METHODS

This was a multicentre, randomized, double-blind, placebo-controlled trial comprising a 52-week core study with a 4-week, active treatment-free washout followed by a 52-week extension study with another washout period conducted in 131 drug-naïve patients with T2DM and mild hyperglycaemia [glycosylated haemoglobin (HbA(1c)) 6.2-7.2%]. All patients received lifestyle counselling at each study visit. Efficacy and tolerability were assessed during visits at weeks 0 (core study baseline), 4, 8, 12, 16, 24, 32, 40 and 52 of active treatment; at week 56 (i.e. after the first washout period); at weeks 68, 80, 96 and 108 and at week 112 (i.e. after the second washout period). Standard meal tests were also performed at weeks 0, 24, 52, 56, 80, 108 and 112 to assess postprandial glycaemia and beta-cell function, which was quantified by glucose area under the curve (AUC(0-2) (h))/insulin secretory rate (ISR) AUC(0-2) (h) (ISR/G). Changes from baseline and between-treatment differences (placebo-adjusted changes from baseline during vildagliptin treatment) were analysed by ancova.

RESULTS

The placebo-adjusted change from week 0 in HbA(1c) was -0.3 +/- 0.1% after 1 year of vildagliptin treatment (p < 0.001) and -0.5 +/- 0.2% after 2 years (p = 0.008). The placebo-adjusted change from core study baseline in fasting plasma glucose, in glucose AUC(0-2) (h) and in the beta-cell function parameter, ISR/G, tended to be greater after 2 years than after 1 year of treatment with vildagliptin. Even after a 4-week washout, the placebo-adjusted change from week 0 to week 112 in ISR/G was 3.2 +/- 1.6 pmol/min/m(2)/mM (p = 0.058) and the placebo-adjusted difference in the change from week 0 to week 112 in HbA(1c) was -0.3 +/- 0.1% (p = 0.051). The incidences of adverse events (AEs), serious AEs and discontinuations because of AEs were similar in the two treatment groups, and hypoglycaemic episodes were reported by no patient receiving vildagliptin and by two patients receiving placebo.

CONCLUSIONS

In drug-naïve patients with mild hyperglycaemia, 2-year treatment with vildagliptin 50 mg once daily attenuated the progressive loss of glycaemic control seen in patients receiving only lifestyle counselling (and placebo). This appears to be because of a corresponding attenuation of the deterioration of beta-cell function as assessed by ISR/G.

Effects of vildagliptin on glucose control in patients with type 2 diabetes inadequately controlled with a sulphonylurea

AIM

To compare the efficacy and tolerability of vildagliptin vs. placebo in patients with type 2 diabetes mellitus (T2DM) who are inadequately controlled [haemoglobin A(1c) (HbA(1c)) 7.5 to 11%] with prior sulphonylurea (SU) monotherapy.

METHODS

This 24-week, multicentre, randomized, double-blind, placebo-controlled study assessed the effects of the dipeptidyl peptidase-4 inhibitor vildagliptin (50 mg given once or twice daily) vs. placebo added to glimepiride (4 mg once daily) in 515 patients with T2DM. Adjusted mean changes from baseline to end-point (AMDelta) in HbA(1c), fasting plasma glucose, fasting lipids and body weight were compared by analysis of covariance.

RESULTS

The between-group difference (vildagliptin - placebo) in AMDelta HbA(1c) was -0.6 +/- 0.1% in patients receiving vildagliptin 50 mg daily and -0.7 +/- 0.1% in those receiving 100 mg daily (p < 0.001 vs. placebo for both). Greater efficacy was seen in patients > or =65 years of age (-0.7 +/- 0.1% and -0.8 +/- 0.2% for 50 and 100 mg daily respectively) and in patients with baseline HbA(1c) > 9% (Delta = -1.0 +/- 0.2% and -0.9 +/- 0.2% for 50 and 100 mg daily respectively). Relative to placebo, patients receiving vildagliptin also had improvements in beta-cell function and postprandial glucose, with small changes in fasting lipids and body weight. The incidences of adverse events (AEs) (67.1, 66.3 and 64.2%) and serious AEs (2.9, 2.4 and 5.1%) were similar in patients receiving 50 mg vildagliptin, 100 mg vildagliptin or placebo respectively. The incidence of hypoglycaemic events was low but slightly higher in the group receiving vildagliptin 100 mg (3.6%) than in the group receiving vildagliptin 50 mg (1.2%) or placebo (0.6%).

CONCLUSIONS

In patients with T2DM inadequately controlled with prior SU monotherapy, addition of vildagliptin (50 or 100 mg daily) to glimepiride (4 mg once daily) improves glycaemic control and is well tolerated. Addition of vildagliptin 50 mg daily to SU monotherapy may be a particularly attractive therapy in elderly patients.

Incretin-based therapies in type 2 diabetes mellitus

CONTEXT

Glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide are incretins secreted from enteroendocrine cells postprandially in part to regulate glucose homeostasis. Dysregulation of these hormones is evident in type 2 diabetes mellitus (T2DM). Two new drugs, exenatide (GLP-1 mimetic) and sitagliptin [dipeptidyl peptidase (DPP) 4 inhibitor], have been approved by regulatory agencies for treating T2DM. Liraglutide (GLP-1 mimetic) and vildagliptin (DPP 4 inhibitor) are expected to arrive on the market soon.

EVIDENCE ACQUISITION

The background of incretin-based therapy and selected clinical trials of these four drugs are reviewed. A MEDLINE search was conducted for published articles using the key words incretin, glucose-dependent insulinotropic polypeptide, GLP-1, exendin-4, exenatide, DPP 4, liraglutide, sitagliptin, and vildagliptin.

EVIDENCE SYNTHESIS

Exenatide and liraglutide are injection based. Three-year follow-up data on exenatide showed a sustained weight loss and glycosylated hemoglobin (HbA(1c)) reduction of 1%. Nausea and vomiting are common. Results from phase 3 studies are pending on liraglutide. Sitagliptin and vildagliptin are orally active. In 24-wk studies, sitagliptin reduces HbA(1c) by 0.6-0.8% as monotherapy, 1.8% as initial combination therapy with metformin, and 0.7% as add-on therapy to metformin. Vildagliptin monotherapy lowered HbA(1c) by 1.0-1.4% after 24 wk. Their major side effects are urinary tract and nasopharyngeal infections and headaches. Exenatide and liraglutide cause weight loss, whereas sitagliptin and vildagliptin do not.

CONCLUSIONS

The availability of GLP-1 mimetics and DPP 4 inhibitors has increased our armamentarium for treating T2DM. Unresolved issues such as the effects of GLP-1 mimetics and DPP 4 inhibitors on beta-cell mass, the mechanism by which GLP-1 mimetics lowers glucagon levels, and exactly how DPP 4 inhibitors lead to a decline in plasma glucose levels without an increase in insulin secretion, need further research.

Combination pharmacotherapy with incretins: what works best and when?

The incretin hormone glucagon-like peptide-1 agonists and dipeptidyl peptidase-4 inhibitors fill an unaddressed therapeutic gap in the treatment of type 2 diabetes mellitus (T2DM) by potentiating insulin secretion in pancreatic beta cells, suppressing glucagon secretion, delaying gastric emptying, and reducing appetite. The incretin therapies, alone or in combination with metformin and/or thiazolidinediones, yield improved glycemic control without risk of hypoglycemia and the potential for weight neutrality or even weight loss. New incretin-based approaches offer promising new strategies for treating T2DM by recruiting new, physiologically based mechanisms of action for glucoregulation in the context of a favorable safety profile.

Multidisciplinary interventions: mapping new horizons in diabetes care

More than 20 million people in the United States, or 7% of the population, have diabetes, with health care and work-related costs estimated to be $174 billion in 2007. Obesity constitutes one of the major driving factors behind this epidemic. Most drugs currently used to treat diabetes address the primary metabolic defects in type 2 diabetes mellitus, which are insulin resistance and pancreatic islet dysfunction. Incretin augmentation therapies, such as glucagon-like peptide-1 receptor agonists and dipeptidyl peptidase IV inhibitors, restore glucose homeostasis by addressing some of the unmet needs in diabetes therapies related to alpha-cell dysfunction and chronic beta-cell dysfunction. This new group of drugs offers certain advantages because its use is characterized by a low incidence of hypoglycemia and the absence of weight gain. Moreover, the use of fixed-dose combinations of dipeptidyl peptidase IV inhibitors with other oral antidiabetic agents seems very attractive to patients because of their reduced pill intake and minimized financial burden, which may improve adherence. An efficient strategy to slow down the epidemic of diabetes must include these emerging therapies and regimens, coupled with intensive patient education that includes information on treatment benefits and adverse effects, medication costs, and medication regimen complexity.

Robust improvements in fasting and prandial measures of beta-cell function with vildagliptin in drug-naïve patients: analysis of pooled vildagliptin monotherapy database

AIM

To assess the effects of 24-week treatment with vildagliptin on measures of beta-cell function in a broad spectrum of drug-naïve patients with type 2 diabetes (T2DM).

METHODS

Data from all double-blind, multicentre, randomized, placebo- or active-controlled trials conducted in drug-naïve patients with T2DM were pooled from all patients receiving monotherapy with vildagliptin (100 mg daily: 50 mg twice daily or 100 mg once daily, n = 1855) or placebo (n = 347). Fasting measures of beta-cell function [homeostasis model assessment of beta-cell function (HOMA-B) and proinsulin : insulin ratio] were assessed in the overall pooled monotherapy population. Standard meal tests were performed at baseline and week 24 in a subset of patients, and effects of vildagliptin (100 mg daily, n = 227) on dynamic (meal test-derived) measures of beta-cell function [insulin secretion rate relative to glucose (ISR/G) and insulinogenic indices] were assessed relative to baseline and vs. placebo (n = 29).

RESULTS

In the overall population, vildagliptin significantly increased HOMA-B both relative to baseline [adjusted mean change (AMDelta) = 10.3 +/- 1.5] and vs. placebo (between-treatment difference in AMDelta = 11.5 +/- 4.5, p = 0.01) and significantly decreased the proinsulin : insulin ratio relative to baseline (AMDelta = -0.05 +/- 0.01) and vs. placebo (between-treatment difference in AMDelta = -0.09 +/- 0.02, p < 0.001). Relative to baseline, vildagliptin monotherapy significantly increased all meal test-derived parameters, and ISR/G (between-treatment difference in AMDelta = 9.8 +/- 2.8 pmol/min/m(2)/mM, p < 0.001) and the insulinogenic index(0-peak glucose) (between-treatment difference in AMDelta = 0.24 +/- 0.05 pmol/mmol, p = 0.045) were significantly increased vs. placebo.

CONCLUSIONS

Vildagliptin monotherapy consistently produced robust improvements in both fasting and meal test-derived measures of beta-cell function across a broad spectrum of drug-naïve patients with T2DM. All Phase III trials described (NCT 00099905, NCT 00099866, NCT 00099918, NCT 00101673, NCT 00101803 and NCT 00120536) are registered with ClinicalTrials.gov.

Accelerating drug development using biomarkers: a case study with sitagliptin, a novel DPP4 inhibitor for type 2 diabetes

The leveraged use of biomarkers presents an opportunity in understanding target engagement and disease impact while accelerating drug development. For effective integration in drug development, it is essential for biomarkers to aid in the elucidation of mechanisms of action and disease progression. The recent years have witnessed significant progress in biomarker selection, validation, and qualification, while enabling surrogate and clinical endpoint qualification and application. Biomarkers play a central role in target validation for novel mechanisms. They also play a central role in the learning/confirming paradigm, particularly when utilized in concert with pharmacokinetic/pharmacodynamic modeling. Clearly, these attributes make biomarker integration attractive for scientific and regulatory applications to new drug development. In this review, applications of proximal, or target engagement, and distal, or disease-related, biomarkers are highlighted using the example of the recent development of sitagliptin for type 2 diabetes, wherein elucidation of target engagement and disease-related biomarkers significantly accelerated sitagliptin drug development. Importantly, use of biomarkers as tools facilitated design of clinical efficacy trials while streamlining dose focus and optimization, the net impact of which reduced overall cycle time to filing as compared to the industry average.

Efficacy and tolerability of vildagliptin in drug-naïve patients with type 2 diabetes and mild hyperglycaemia*

AIM

This study was conducted to assess efficacy and tolerability of vildagliptin in drug-naïve patients with type 2 diabetes and mild hyperglycaemia.

METHODS

Multicentre, double-blind, randomized, placebo-controlled, parallel-group study of 52-week treatment with vildagliptin (50 mg q.d.) in 306 drug-naïve patients with type 2 diabetes (A1C = 6.2-7.5%). A1C, fasting plasma glucose (FPG) and measures of prandial glucose control and beta-cell function determined during standard meal tests were assessed.

RESULTS

Baseline A1C and FPG averaged 6.7% and 7.1 mmol/l, respectively, in patients randomized to vildagliptin (n = 156) and 6.8% and 7.2 mmol/l in those randomized to placebo (n = 150). A1C decreased modestly in vildagliptin-treated patients (Delta = -0.2 +/- 0.1%) and increased in patients receiving placebo (Delta = 0.1 +/- 0.1%). The between-group difference (vildagliptin - placebo) in adjusted mean change (AM Delta) in A1C was -0.3 +/- 0.1% (p < 0.001). FPG increased in patients receiving placebo (Delta = 0.5 +/- 0.1 mmol/l) and to a significantly lesser extent in vildagliptin-treated patients (between-group difference in AM Delta FPG = -0.4 +/- 0.2 mmol/l, p = 0.032). Relative to placebo, 2-h postprandial glucose (PPG) decreased (-0.9 +/- 0.4 mmol/l, p = 0.012), and insulin secretory rate (ISR) relative to glucose [ISR area under the curve (AUC)(0-2) (h)/glucose AUC(0-2) (h)] increased (+5.0 +/- 1.2 pmol/min/m(2)/mM, p < 0.001). Mean body weight decreased by 0.5 +/- 0.3 kg in vildagliptin-treated patients and by 0.2 +/- 0.3 kg in patients receiving placebo. The side-effect profile of vildagliptin was similar to that of placebo, and one hypoglycaemic episode occurred in one patient receiving placebo.

CONCLUSIONS

In drug-naïve patients with mild hyperglycaemia, relative to placebo, 52-week treatment with vildagliptin 50 mg q.d. significantly decreases A1C, FPG and PPG and improves beta-cell function without weight gain or hypoglycaemia.

Value of the intravenous and oral glucose tolerance tests for detecting subtle impairments in insulin sensitivity and beta-cell function in former gestational diabetes

OBJECTIVE

Women with former gestational diabetes mellitus (fGDM) often show defects in both insulin sensitivity and beta-cell function but it is not clear which defect plays the major role or which appears first. This might be because fGDM women are often studied as a unique group and not divided according to their glucose tolerance. Different findings might also be the result of using different tests. Our aim was to study insulin sensitivity and beta-cell function with two independent glucose tolerance tests in fGDM women divided according to their glucose tolerance.

DESIGN AND PATIENTS

A total of 108 fGDM women divided into normal glucose tolerance (IGT; N = 82), impaired glucose metabolism (IGM; N = 20) and overt type 2 diabetes (T2DM; N = 6) groups, and 38 healthy control women (CNT) underwent intravenous (IVGTT) and oral glucose tolerance tests (OGTT). Measurements Insulin sensitivity and beta-cell function were assessed by both the IVGTT and the OGTT.

RESULTS

Both tests revealed impaired insulin sensitivity in the normotolerant group compared to controls (IVGTT: 4.2 +/- 0.3 vs. 5.4 +/- 0.4 10(-4) min(-1) (microU/ml)(-1); OGTT: 440 +/- 7 vs. 472 +/- 9 ml min(-1) m(-2)). Conversely, no difference was found in beta-cell function from the IVGTT. However, some parameters of beta-cell function by OGTT modelling analysis were found to be impaired: glucose sensitivity (106 +/- 5 vs. 124 +/- 7 pmol min(-1) m(-2) mm(-1), P = 0.0407) and insulin secretion at 5 mm glucose (168 +/- 9 vs. 206 +/- 10 pmol min(-1) m(-2), P = 0.003).

CONCLUSIONS

Both insulin sensitivity and beta-cell function are impaired in normotolerant fGDM but the subtle defect in beta-cell function is disclosed only by OGTT modelling analysis.

The islet enhancer vildagliptin: mechanisms of improved glucose metabolism

Vildagliptin is a potent, selective and reversible inhibitor of dipeptidyl peptidase-4 (DPP-4), the enzyme responsible for rapid inactivation of the incretin hormones glucagon-like peptide-1 (GLP-1) and gastric inhibitory polypeptide (GIP). GLP-1 and GIP are important for the maintenance of normal glucose homeostasis as they enhance the sensitivity of insulin (beta-cell) and glucagon (alpha-cell) secretion to glucose. The delicate balance that is achieved by the incretin hormones is disturbed in type 2 diabetes mellitus (T2DM). Mechanistic studies of vildagliptin performed to characterise the effects of DPP-4 inhibition on pancreatic islet function and glucose metabolism have found that vildagliptin produces dose-dependent reductions in DPP-4; these result in persistent levels of active GLP-1 and GIP in the circulation leading to improved beta-cell sensitivity to glucose and glucose-dependent insulin secretion, and improved alpha-cell sensitivity to glucose and reduction in inappropriate glucagon secretion. These islet effects in turn lead to a reduction of the inappropriate endogenous glucose production and glucose utilisation during meals, resulting in improved glucose tolerance, and to a reduction of the inappropriate endogenous glucose production during the postabsorptive period that contributes to a reduced fasting hyperglycaemia. These islet effects are associated with improved insulin sensitivity and reduced meal-related hypertriglyceridaemia. In contrast, the GLP-1 effect of significantly delaying gastric emptying was not evident with vildagliptin treatment. The metabolic benefits of vildagliptin observed in T2DM are also evident in subjects with impaired glucose tolerance. Hence, vildagliptin improves glucose metabolism mainly by improving islet function.

Effect of food on the pharmacokinetics of a vildagliptin/metformin (50/1000 mg) fixed-dose combination tablet in healthy volunteers

OBJECTIVE

Vildagliptin is an orally active, potent and selective DPP-4 inhibitor that improves glycemic control in patients with type 2 diabetes by increasing alpha- and beta-cell responsiveness to glucose.

RESEARCH DESIGN AND METHODS

This open-label, single-center, randomized, two-period crossover study in healthy subjects (n=23) ages 18-45 years investigated the effect of food on the pharmacokinetics of vildagliptin and metformin following administration of a vildagliptin/metformin (50/1000 mg) fixed-dose combination tablet.

RESULTS

Administration of the fixed-dose combination tablet following a high-fat meal had no effect on vildagliptin AUC(0-infinity) (ratio of geometric mean for fed:fasted state, 1.10 [90% CI 1.03, 1.18]), C(max) (ratio of means 0.98 [90% CI 0.85, 1.13]) or median t(max) (2.5 h in fed and fasted states). The rate of absorption of metformin was decreased when given with food, as reflected by the prolonged t(max) (2-4 h) and reduction in C(max) (by 26%), but the extent of absorption was not changed. The food effect on the metformin component of the fixed-dose combination tablets was consistent with, but of a lesser magnitude compared with data stated.

CONCLUSIONS

The vildagliptin/metformin (50/1000 mg) fixed-dose combination tablet can be administered in the same manner as metformin, and can be recommended to be taken with meals to reduce the gastrointestinal symptoms associated with metformin.

Non-linear increase in GLP-1 levels in response to DPP-IV inhibition in healthy adult subjects

AIM

Dipeptidyl peptidase-IV (DPP-IV) inhibitors represent a new promising therapeutic intervention for the treatment of type 2 diabetes mellitus. The aim of this study was to investigate the effects of DPP-IV inhibition by PF-00734200, a potent competitive DPP-IV inhibitor, on the dynamics of DPP-IV activity and glucagon-like peptide-1 (GLP-1) kinetics in healthy adult subjects.

METHODS

This was a prospective randomized, crossover, placebo-controlled, ascending, single, oral dose study conducted at a clinical research centre. Twenty-seven healthy adult subjects were randomized to receive placebo or PF-00734200 with doses ranging from 0.3 to 300 mg (n = 9 per dose group). Pharmacokinetic and pharmacodynamic end points (DPP-IV activity and GLP-1) were measured prior to, and various times after, dosing.

RESULTS

PF-00734200 was well tolerated in all subjects. Pharmacokinetics (PK) data indicate that the drug was rapidly absorbed and declined in a biphasic fashion. Mean maximum concentration and area under concentration curve appeared to increase with doses proportionally. DPP-IV inhibition increased with PF-00734200 concentrations, which can be described by an E(max) model with EC50 approximately being 14 ng/ml. DPP-IV inhibition led to greater GLP-1 level accumulation compared with placebo. Plasma GLP-1 levels stimulated by meals were augmented by DPP-IV inhibition. However, the increase in GLP-1 with DPP-IV inhibition was non-linear and maximized at 10 mg, a dose which resulted in about 75% weighted average DPP-IV inhibition over 24 h and a 2.3-fold increase in GLP-1 over placebo. Moreover, even with near complete inhibition of DPP-IV for over 24 h at the highest PF-00734200 dose levels, the GLP-1 levels actually declined during the night compared with postdinner levels.

CONCLUSION

DPP-IV inhibition by PF-00734200 resulted in a non-linear increase in plasma GLP-1 level, suggesting GLP-1 levels may be limited by meal stimulus or by production capacity. In addition, GLP-1 level declined even during maximal DPP-IV inhibition, suggesting that there may be additional pathways of GLP-1 elimination other than DPP-IV enzymatic breakdown.

Vildagliptin: the evidence for its place in the treatment of type 2 diabetes mellitus

INTRODUCTION

Type 2 diabetes is increasing in prevalence worldwide and is a leading cause of morbidity and mortality, mainly due to the development of complications. Vildagliptin is an inhibitor of dipeptidyl peptidase 4 (DPP-4), a new class of oral antidiabetic agents.

AIMS

To evaluate the role of vildagliptin in the management of type 2 diabetes.

EVIDENCE REVIEW

Clear evidence shows that vildagliptin improves glycemic control (measured by glycosylated hemoglobin and blood glucose levels) more than placebo in adults with type 2 diabetes, either as monotherapy or in combination with metformin. Vildagliptin is as effective as pioglitazone and rosiglitazone, and slightly less effective than metformin, although better tolerated. Further glycemic control is achieved when adding vildagliptin to metformin, pioglitazone, or glimepride. There is evidence that vildagliptin improves beta-cell function and insulin sensitivity. Vildagliptin does not appear to be associated with weight gain or with a higher risk of hypoglycemia than placebo or other commonly used oral antidiabetic agents. Economic evidence is currently lacking.

PLACE IN THERAPY

Vildagliptin improves glycemic control with little if any weight gain or hypoglycemia in adult patients with type 2 diabetes when given alone or in combination with metformin, thiazolidinediones, or sulfonylureas. Since many diabetic patients require combination therapy, the complementary mechanism of action of vildagliptin and other commonly prescribed antidiabetic drugs represents an important new therapeutic option in diabetes management.

The dipeptidyl peptidase-4 inhibitor PHX1149 improves blood glucose control in patients with type 2 diabetes mellitus

AIM

To determine the efficacy and tolerability of PHX1149, a novel dipeptidyl peptidase-4 (DPP4) inhibitor, in patients with type 2 diabetes.

METHODS

This is a multicentre, randomized, double-blind, placebo-controlled, 4-week study in patients with type 2 diabetes with suboptimal metabolic control. Patients with a baseline haemoglobin A(1c) (HbA(1c)) of 7.3 to 11.0% were randomized 1 : 1 : 1 : 1 to receive once-daily oral therapy with either PHX1149 (100, 200 or 400 mg) or placebo; patients were on a constant background therapy of either metformin alone or metformin plus a glitazone.

RESULTS

Treatment with 100, 200 or 400 mg of PHX1149 significantly decreased postprandial glucose area under the curve AUC(0-2 h) by approximately 20% (+0.11 +/- 0.50, -2.08 +/- 0.51, -1.73 +/- 0.49 and -1.88 +/- 0.48 mmol/l x h, respectively, for placebo and 100, 200 and 400 mg (p = 0.002, 0.008 and 0.004 vs. placebo). Postprandial AUC(0-2 h) of intact glucagon-like peptide-1, the principal mediator of the biological effects of DPP4 inhibitors, was increased by 3.90 +/- 2.83, 11.63 +/- 2.86, 16.42 +/- 2.72 and 15.75 +/- 2.71 pmol/l x h, respectively, for placebo and 100, 200 and 400 mg (p = 0.053, 0.001 and 0.002 vs. placebo). Mean HbA(1c) was lower in all dose groups; the placebo-corrected change in the groups receiving 400 mg PHX1149 was -0.28% (p = 0.02). DPP4 inhibition on day 28 was 53, 73 and 78% at 24 h postdose in the groups receiving 100, 200 and 400 mg PHX1149, respectively. There were no differences in adverse events between PHX1149-treated and placebo subjects.

CONCLUSIONS

Addition of the DPP4 inhibitor PHX1149 to a stable regimen of metformin or metformin plus a glitazone in patients with type 2 diabetes was well tolerated and improved blood glucose control.

Comparison of vildagliptin and acarbose monotherapy in patients with Type 2 diabetes: a 24-week, double-blind, randomized trial

AIMS

To compare the efficacy and tolerability of the dipeptidyl peptidase-4 inhibitor, vildagliptin, with the alpha glucosidase inhibitor, acarbose, in drug-naive patients with Type 2 diabetes.

METHODS

This multi-centre, randomized, double-blind, parallel-arm study compared the efficacy and tolerability of vildagliptin (100 mg daily, given as 50 mg twice daily, n = 441) and acarbose (up to 300 mg daily, given as three equally divided doses, n = 220) during 24-week treatment in drug-naive patients with Type 2 diabetes.

RESULTS

Monotherapy with vildagliptin or acarbose decreased glycated haemoglobin (HbA(1c)) (baseline approximately 8.6%) to a similar extent during 24-week treatment. The adjusted mean change from baseline to end-point (AMDelta) in HbA(1c) was -1.4 +/- 0.1% and -1.3 +/- 0.1% in patients receiving vildagliptin and acarbose, respectively, meeting the statistical criterion for non-inferiority (upper limit of 95% confidence interval for between-treatment difference < or = 0.4%). The decrease in fasting plasma glucose was similar with acarbose (-1.5 +/- 0.2 mmol/l) and vildagliptin (-1.2 +/- 0.1 mmol/l). Body weight did not change in vildagliptin-treated patients (-0.4 +/- 0.1 kg) but decreased in acarbose-treated patients (-1.7 +/- 0.2 kg, P < 0.001 vs. vildagliptin). The proportion of patients experiencing any adverse event (AE) was 35% vs. 51% in patients receiving vildagliptin or acarbose, respectively; gastrointestinal AEs were significantly more frequent with acarbose (25.5%) than vildagliptin (12.3%, P < 0.001). No hypoglycaemia was reported for either group.

CONCLUSIONS

Vildagliptin is effective and well tolerated in patients with Type 2 diabetes, demonstrating similar glycaemic reductions to acarbose, but with better tolerability.

Preserving insulin secretion in Type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) is a complex disease characterized by insulin resistance and a progressive decline in β-cell function and mass. Current evidence suggests that β-cell dysfunction is present early in the course of the disease and that this dysfunction, rather than insulin resistance, is primarily responsible for the progression of T2DM. β-cell dysfunction can be accelerated by glucose toxicity, lipotoxicity, oxidative stress, chronic increases in inflammatory mediators and, potentially, the use of sulfonylureas. This review suggests that future efforts to limit the impact of T2DM must focus on strategies to preserve β-cell function. Several interventions have shown promise in this regard, including lifestyle modifications, thiazolidinediones, potassium channel openers, incretin mimetics, cytokine antagonists, bariatric surgery and dipeptidyl peptidase IV inhibitors, although therapeutic insulin remains the most robust and physiological approach.