Comparison between vildagliptin and metformin to sustain reductions in HbA(1c) over 1 year in drug-naïve patients with Type 2 diabetes

Comparing the actions of older and newer therapies on body weight: to what extent should these effects guide the selection of antidiabetic therapy?

BACKGROUND

Type 2 diabetes patients are usually overweight or obese. Further weight gain induced by antidiabetic treatment should be avoided if possible. Much attention has been focussed recently on the potential for GLP-1 mimetics, in particular, to reduce weight.

AIMS

Effects on weight are but one of several important criteria in selecting antidiabetic therapy, however. This review explores the effects on weight of older classes of antidiabetic agents (metformin, sulfonylureas, thiazolidinediones) and the newer drugs acting via the GLP-1 system. Other aspects of their therapeutic profiles and current therapeutic use are reviewed briefly to place effects on weight within a broader context.

FINDINGS

Comparative trials demonstrated weight neutrality or weight reduction with metformin, and weight increases with a sulfonylurea or thiazolidinedione. There was no clinically significant change in weight with DPP-4 inhibitors and a small and variable decrease in weight (about 3 kg or less) with GLP-1 mimetics. Improved clinical outcomes have been demonstrated for metformin and a sulfonylurea (cardiovascular and microvascular benefits, respectively, in the UK Prospective Diabetes Study), and secondary endpoints improved modestly with pioglitazone in the PROactive trial. No outcome benefits have been demonstrated to date with GLP-1-based therapies, and these agents exert little effect on cardiovascular risk factors. Concerns remain over long-term safety of these agents and this must be weighed against any potential benefit on weight management.

CONCLUSIONS

Considering effects on weight within the overall risk-benefit profile of antidiabetic therapies, metformin continues to justify its place at the head of current management algorithms for type 2 diabetes, due to its decades-long clinical evidence base, cardiovascular outcome benefits and low cost.

Dipeptydil peptidase-4 inhibitors in type 2 diabetes: a meta-analysis of randomized clinical trials

BACKGROUND AND AIM

The role of Dipeptidyl Peptidase-4 (DPP-4) inhibitors in the treatment of type 2 diabetes is debated; many recent trials, which were not included in previous meta-analyses, could add relevant information.

METHODS AND RESULTS

All available randomized controlled trials (RCTs), either published or unpublished, performed in type 2 diabetic patients with DPP-4 inhibitors, with a duration >12 weeks were meta-analyzed for HbA1c, BMI, hypoglycemia, and other adverse events. A total of 41 RCTs (9 of which are unpublished) was retrieved and included in the analysis. Gliptins determine a significant improvement of HbA1c in comparison with a placebo (-0.7 [-0.8:-0.6]), with a low risk of hypoglycemia. DPP-4 inhibitors show a similar efficacy in monotherapy and in combination with other agents. The risk of cardiovascular events and all-cause death with DPP-4 inhibitors is 0.76 [0.46-1.28] and 0.78 [0.40-1.51], respectively.

CONCLUSIONS

DPP-4 inhibitors reduce HbA1c, although to a lesser extent than sulphonylureas, with no weight gain and no hypoglycemic risk; further data are needed to assess their long-term safety.

Comparative evaluation of incretin-based antidiabetic medications and alternative therapies to be added to metformin in the case of monotherapy failure

Aims/Introduction:  To compare clinical consequences of using inretin-based medications versus conventional antidiabetic agents as add-on to metformin in case of monotherapy failure in patients with type 2 diabetes.

MATERIALS AND METHODS

  The medical literature including recent abstracts from international diabetes conferences was searched for reports from clinical trials with incretin mimetics (GLP-1 receptor agonists), inhibitors of dipeptidyl peptidase-4 (DPP-4, incretin enhancers) and conventional antidiabtic drugs coadministered with metformin after monotherapy failure. A scoring system is suggested to compare the clinical utility of using incretin-based versus conventional antidiabetic agents in this situation.

RESULTS

  Incretin mimetics and DPP-4 inhibitors on top of metformin treatment help achieve glycaemic control comparable to other efficient antidiabetic drugs, both if separate or head-to-head trials were considered. Incretin-based antidiabetic drugs did not cause hypoglycaemia (different from sulfonylureas, meglitinides and insulin) and weight gain (different from sulfonylureas, meglitinides, thiazolidinediones, and insulin). DPP-4 inhibitors were weight neutral, incretin mimetics lead to weight loss. The clinical profile of incretin-based medications received the highest scores, followed by α-glucosidase inhibitors, with far lower scores assigned to insulin, glitazones, and sulfonyureas (in this order).

CONCLUSIONS

  Based on the results from clinical trials, incretin-based medications have been shown to be efficacious antidiabetic drugs with a favourable adverse event and tolerability profile. This leads to high scores using a novel system paying attention to multiple facets contributing to the selection of antidiabetic drugs for general recommendation and individual treatment choices.

Risk of fatal and nonfatal lactic acidosis with metformin use in type 2 diabetes mellitus

BACKGROUND

Metformin is an oral anti-hyperglycemic agent that has been shown to reduce total mortality compared to other anti-hyperglycemic agents, in the treatment of type 2 diabetes mellitus. Metformin, however, is thought to increase the risk of lactic acidosis, and has been considered to be contraindicated in many chronic hypoxemic conditions that may be associated with lactic acidosis, such as cardiovascular, renal, hepatic and pulmonary disease, and advancing age.

OBJECTIVES

To assess the incidence of fatal and nonfatal lactic acidosis, and to evaluate blood lactate levels, for those on metformin treatment compared to placebo or non-metformin therapies.

SEARCH STRATEGY

A comprehensive search was performed of electronic databases to identify studies of metformin treatment. The search was augmented by scanning references of identified articles, and by contacting principal investigators.

SELECTION CRITERIA

Prospective trials and observational cohort studies in patients with type 2 diabetes of least one month duration were included if they evaluated metformin, alone or in combination with other treatments, compared to placebo or any other glucose-lowering therapy.

DATA COLLECTION AND ANALYSIS

The incidence of fatal and nonfatal lactic acidosis was recorded as cases per patient-years, for metformin treatment and for non-metformin treatments. The upper limit for the true incidence of cases was calculated using Poisson statistics. In a second analysis lactate levels were measured as a net change from baseline or as mean treatment values (basal and stimulated by food or exercise) for treatment and comparison groups. The pooled results were recorded as a weighted mean difference (WMD) in mmol/L, using the fixed-effect model for continuous data.

MAIN RESULTS

Pooled data from 347 comparative trials and cohort studies revealed no cases of fatal or nonfatal lactic acidosis in 70,490 patient-years of metformin use or in 55,451 patients-years in the non-metformin group. Using Poisson statistics the upper limit for the true incidence of lactic acidosis per 100,000 patient-years was 4.3 cases in the metformin group and 5.4 cases in the non-metformin group. There was no difference in lactate levels, either as mean treatment levels or as a net change from baseline, for metformin compared to non-metformin therapies.

AUTHORS' CONCLUSIONS

There is no evidence from prospective comparative trials or from observational cohort studies that metformin is associated with an increased risk of lactic acidosis, or with increased levels of lactate, compared to other anti-hyperglycemic treatments.

The incretin system and cardiometabolic disease

Rates of type 2 diabetes, obesity and their associated detrimental cardiovascular effects are rapidly increasing. Despite the availability of several treatment options for type 2 diabetes and the use of intensive regimens combining several antidiabetic drugs, less than one-half of all patients reach a target glycosylated hemoglobin level of less than 7%. Disease progression due to ongoing deterioration of pancreatic islet cell health and beta-cell function is likely responsible. Therefore, there is a need to identify new pharmacological compounds that may not only treat hyperglycemia, but may also correct impaired glucose homeostasis and preserve endogenous beta-cell function. Identification and characterization of the incretin system and its effect on glucose homeostasis have resulted in the development of new antidiabetic agents that target these concerns. The current review examines the incretin effect and the pharmacological agents that have been developed based on the understanding of this physiological system. The influence of incretins on the cardiovascular system beyond the proatherogenic effect of type 2 diabetes will also be discussed.

A comparison of efficacy and safety of vildagliptin and gliclazide in combination with metformin in patients with Type 2 diabetes inadequately controlled with metformin alone: a 52-week, randomized study

AIM

To demonstrate non-inferiority of vildagliptin compared with gliclazide, as an add-on therapy, in patients with Type 2 diabetes inadequately controlled with metformin in a 52-week, randomized, double-blind, active-controlled study.

METHODS

Patients receiving a stable dose of metformin (> or = 1500 mg) were randomized (1 : 1) to receive vildagliptin (50 mg twice daily; n = 513) or gliclazide (up to 320 mg/day; n = 494).

RESULTS

Non-inferiority of vildagliptin was demonstrated (95% confidence interval -0.11%, 0.20%) with a mean change (se) from baseline glycated haemoglobin (HbA(1c)) (approximately 8.5% in both groups) to a 52-week endpoint of -0.81% (0.06) with vildagliptin and -0.85% (0.06) with gliclazide. Although a similar proportion of patients reached HbA(1c) < 7.0%, the total number of hypoglycaemic events was lower in the vildagliptin group (6 vs. 11 events). Vildagliptin was non-inferior (margin 0.6 mmol/l) to gliclazide in reducing fasting plasma glucose (1.31 vs. 1.52 mmol/l, P = 0.257). The overall incidence of any adverse events was similar in both groups (approximately 61%), but the number of serious adverse events was higher in the gliclazide group (8.7 vs. 6.7%). The number of patients who discontinued as a result of an unsatisfactory effect was higher in the vildagliptin group (n = 22 vs. 13, respectively) compared with gliclazide, but vildagliptin did not induce weight gain.

CONCLUSION

In patients with Type 2 diabetes inadequately controlled with metformin, addition of vildagliptin provided similar HbA(1c)-lowering efficacy compared with gliclazide after 52 weeks of treatment. Although both treatments were well tolerated, vildagliptin-treated patients had fewer hypoglycaemic events and did not gain weight.

Regulation of lipid metabolism by energy availability: a role for the central nervous system

The central nervous system (CNS) is crucial in the regulation of energy homeostasis. Many neuroanatomical studies have shown that the white adipose tissue (WAT) is innervated by the sympathetic nervous system, which plays a critical role in adipocyte lipid metabolism. Therefore, there are currently numerous reports indicating that signals from the CNS control the amount of fat by modulating the storage or oxidation of fatty acids. Importantly, some CNS pathways regulate adipocyte metabolism independently of food intake, suggesting that some signals possess alternative mechanisms to regulate energy homeostasis. In this review, we mainly focus on how neuronal circuits within the hypothalamus, such as leptin- ghrelin-and resistin-responsive neurons, as well as melanocortins, neuropeptide Y, and the cannabinoid system exert their actions on lipid metabolism in peripheral tissues such as WAT, liver or muscle. Dissecting the complicated interactions between peripheral signals and neuronal circuits regulating lipid metabolism might open new avenues for the development of new therapies preventing and treating obesity and its associated cardiometabolic sequelae.

Reaching HbA1c goals with saxagliptin in combination with other oral antidiabetic drugs

A large percentage of individuals with type 2 diabetes in the United States are not reaching their glycemic goals. In response to data from large outcomes trials and newer classes of therapeutic agents, various organizations and opinion-forming bodies recently updated their clinical practice recommendations for type 2 diabetes. The recommendations, as set by the American Diabetes Association (ADA)/European Association for the Study of Diabetes (EASD), the American Association of Clinical Endocrinologists/American College of Endocrinology, and the Canadian Diabetes Association, are similar in their emphasis on lifestyle modification and the importance of treating fasting and postprandial glucose, both of which are significant contributors to achieving glycated hemoglobin (HbA1c) targets. However, the recommendations differ in focus, depth, and specific treatment approaches. With the exception of the ADA/EASD consensus, dipeptidyl peptidase-4 (DPP-4) inhibitors have been included as alternative first- or second-line therapy due, in part, to their glucose-dependent mechanism of action that complements the actions of other oral antidiabetic drugs (OADs). The DPP-4 inhibitor, saxagliptin, demonstrates significant glycemia-lowering effects as monotherapy and in combination therapy, is weight neutral and well tolerated, and has a low risk of hypoglycemia. The added efficacy of saxagliptin in combination with other OADs in improving glycemic parameters has resulted in a significant proportion of patients achieving an HbA1c <7% versus monotherapy or active comparator. Combination therapy with saxagliptin can thus offer a potential advantage in achieving glycemic goals for the majority of patients with type 2 diabetes without additional tolerability concerns.

Current developments in the treatment of diabetes: the incretin therapies

The prevalence of type 2 diabetes in the UK has increased enormously over recent years and is closely associated with obesity and other risk factors for cardiovascular disease. The incretin system, which contributes significantly to the insulin response in healthy individuals, but is impaired in individuals with diabetes, offers a target for the development of agents that address many aspects of diabetes. These agents are broadly split into two categories — the glucagon-like polypeptide-1 (GLP-1) receptor agonists and the dipeptidyl peptidase-4 (DPP-4) inhibitors. The DPP-4 inhibitors sitagliptin and vildagliptin, along with the GLP-1 receptor agonists exenatide and liraglutide are currently approved for use and offer effective glycaemic control with a low risk of hypoglycaemia. GLP-1 receptor agonists may offer further benefits over both DPP-4 inhibitors and conventional therapies, such as reductions in body weight and blood pressure. Here we review the incretin system (with particular reference to GLP-1) and consider the development of these two classes of antidiabetic therapy, discussing the safety and efficacy of some of the latest available GLP-1 receptor agonists and DPP-4 inhibitors.

Dipeptidyl peptidase-4 inhibitors in the management of type 2 diabetes: safety, tolerability, and efficacy

Although glycemic control is an important and effective way to prevent and minimize the worsening of diabetes-related complications, type 2 diabetes is a progressive disease which often proves difficult to manage. Most affected patients will eventually require therapy with multiple medications in order to reach appropriate glycemic targets. The dipeptidyl peptidase-4 (DPP-4) inhibitors constitute a relatively new class of oral medications for the treatment of type 2 diabetes, which has become widely incorporated into clinical practice. This review summarizes the available data on the efficacy, safety, and tolerability of these medications.

Vildagliptin in clinical practice: a review of literature

Vildagliptin is the second member of the DPP-IV inhibitor class of drugs licensed for the treatment of type 2 diabetes mellitus (T2DM). The novel action of these drugs has promoted a new outlook in the pathobiology of T2DM. This review undertakes to examine the clinical studies published to date, with the aim of evaluating the position of vildagliptin among the drugs that are now available to treat this common dysmetabolic state.

Risk of fatal and nonfatal lactic acidosis with metformin use in type 2 diabetes mellitus

BACKGROUND

Metformin is an oral anti-hyperglycemic agent that has been shown to reduce total mortality compared to other anti-hyperglycemic agents, in the treatment of type 2 diabetes mellitus. Metformin, however, is thought to increase the risk of lactic acidosis, and has been considered to be contraindicated in many chronic hypoxemic conditions that may be associated with lactic acidosis, such as cardiovascular, renal, hepatic and pulmonary disease, and advancing age.

OBJECTIVES

To assess the incidence of fatal and nonfatal lactic acidosis, and to evaluate blood lactate levels, for those on metformin treatment compared to placebo or non-metformin therapies.

SEARCH STRATEGY

A comprehensive search was performed of electronic databases to identify studies of metformin treatment. The search was augmented by scanning references of identified articles, and by contacting principal investigators.

SELECTION CRITERIA

Prospective trials and observational cohort studies in patients with type 2 diabetes of least one month duration were included if they evaluated metformin, alone or in combination with other treatments, compared to placebo or any other glucose-lowering therapy.

DATA COLLECTION AND ANALYSIS

The incidence of fatal and nonfatal lactic acidosis was recorded as cases per patient-years, for metformin treatment and for non-metformin treatments. The upper limit for the true incidence of cases was calculated using Poisson statistics. In a second analysis lactate levels were measured as a net change from baseline or as mean treatment values (basal and stimulated by food or exercise) for treatment and comparison groups. The pooled results were recorded as a weighted mean difference (WMD) in mmol/L, using the fixed-effect model for continuous data.

MAIN RESULTS

Pooled data from 347 comparative trials and cohort studies revealed no cases of fatal or nonfatal lactic acidosis in 70,490 patient-years of metformin use or in 55,451 patients-years in the non-metformin group. Using Poisson statistics the upper limit for the true incidence of lactic acidosis per 100,000 patient-years was 4.3 cases in the metformin group and 5.4 cases in the non-metformin group. There was no difference in lactate levels, either as mean treatment levels or as a net change from baseline, for metformin compared to non-metformin therapies.

AUTHORS' CONCLUSIONS

There is no evidence from prospective comparative trials or from observational cohort studies that metformin is associated with an increased risk of lactic acidosis, or with increased levels of lactate, compared to other anti-hyperglycemic treatments.

DPP-4 inhibitors in clinical practice

Type 2 diabetes is a very common worldwide disorder, with major consequences for patients, society, and health care services. Good glycemic control is an important aspect of diabetes management because it has a significant impact on diabetes-related microvascular and possibly macrovascular complications. Based on our understanding of the pathogenesis of diabetes, multiple pharmacological interventions have been developed in the past 60 years. Although effective, none have had a lasting effect on glycemic control because of the progressive nature of type 2 diabetes requiring combination therapies and insulin treatment. In addition, several pharmacologic interventions have undesirable side effects, including hypoglycemia and weight gain. Drugs targeting the incretin pathway are the latest addition to the available antidiabetes agents. Incretin-based therapy is either delivered orally (dipeptidyl peptidase-4 [DPP-4]) inhibitors or injected subcutaneously (glucagon-like peptide-1 [GLP-1] mimetics and analogues). Dipeptidyl peptidase-4 inhibitors are effective either as a single or combination therapy in lowering glycated hemoglobin, fasting and postprandial glucose levels, with a low incidence of hypoglycemia and no weight gain. There are 3 DPP-4 inhibitors currently available (sitagliptin, saxagliptin, and vildagliptin), with more expected to be available in the future. In this article, we review the scientific background for incretin-based therapy and the available evidence regarding the role and efficacy of DPP-4 inhibitors in the treatment of patients with type 2 diabetes.

Future perspectives for insulinotropic agents in the treatment of type 2 diabetes-DPP-4 inhibitors and sulphonylureas

The introduction of dipeptidyl-peptidase IV inhibitors (DPP-4 inhibitors) brought a novel class of insulinotropic agents into the treatment options for type 2 diabetes. This paper compares the actions, clinical efficacy and safety of sulphonylureas with those of the DPP-4 inhibitors. First, the mode of action of both classes of antidiabetic agents is described. Then clinical studies for both substances in monotherapy and combination therapies are compared concerning their effects on glycaemic parameters and long-term duration of action. Hypoglycaemia incidence and other adverse effects are compared and data on cardiovascular parameters and endpoints are summarized. The effects of sulphonylureas and DPP-4 inhibitors on beta-cell function and beta-cell mass are highlighted. The present and future indications for both sulphonylureas and DPP-4 inhibitors are discussed.

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.

Pharmacotherapy of hyperglycemia

Type 2 diabetes mellitus (T2DM) is a chronic, progressive disorder that affects more than 230 million people worldwide and is expected to affect 366 million by 2030. Both the prevalence of T2DM and the cost of its long term complications has driven the focus and emphasis on treatments aimed at reducing hyperglycemia and controlling hypertension and dyslipidemia. In the last 5 years new glucose lowering drugs acting on novel pathways have been developed, licensed and launched. These drugs include the glucagon-like peptide (GLP-1) agonists, exenatide, and dipeptidyl peptidase (DPP-IV) inhibitors such as sitagliptin and saxagliptin. This review describes current approaches to T2DM treatment, focusing on newer agents which tend to be associated with less hypoglycemia and possible weight loss, and addresses the potential roles of novel oral pharmacologic agents in the late-stages of development that might provide new options for the management of this disease.

Differential chemistry (structure), mechanism of action, and pharmacology of GLP-1 receptor agonists and DPP-4 inhibitors

OBJECTIVE

To review the pharmacology (absorption, metabolism, distribution, elimination, and contraindications) of incretin-based agents currently available and in regulatory review for the treatment of patients with type 2 diabetes.

DATA SOURCES

Medline search of all relevant clinical and review articles.

STUDY SELECTION

English-language articles pertinent to the pharmacology, pharmacodynamics, pharmacokinetics, efficacy, and safety of glucagon-like peptide-1 (GLP-1) agonists and dipeptidyl peptidase-4 (DPP-4) inhibitors were reviewed for relevance.

DATA EXTRACTION

Data pertinent to the pharmacology, pharmacodynamics, pharmacokinetics, efficacy, and safety of GLP-1 agonists and DPP-4 inhibitors were extracted and used.

DATA SYNTHESIS

Incretin hormones are secreted from the gastrointestinal tract following meal ingestion, the two most important of which are glucose-dependent insulinotropic polypeptide (GIP) and GLP-1. Patients with type 2 diabetes have an impaired response to GIP, while intravenous GLP-1 has been shown to increase insulin secretion in response to elevated glucose levels. Incretin-based agents include GLP-1 receptor agonists, which mimic endogenous GLP-1, and DPP-4 inhibitors (e.g., sitagliptin, vildagliptin, saxagliptin, alogliptin), which inhibit the breakdown of endogenous incretin hormones. GLP-1 receptor agonists stimulate insulin secretion in a glucose-dependent manner and suppress glucagon secretion with a low risk of hypoglycemia. The GLP-1 receptor agonists are further differentiated as either human analogues (e.g., liraglutide) or synthetic exendin-based mimetics (e.g., exenatide). These agents delay gastric emptying and may beneficially affect satiety and are thus associated with weight reduction.

CONCLUSION

GLP-1 receptor agonists and DPP-4 inhibitors facilitate therapy intensification and achievement of established glycemic goals. They enhance postprandial and fasting glycemic control, and use may improve beta-cell function and possibly preserve beta-cell mass. GLP-1 receptor agonists may also have favorable effects on blood pressure. They may be introduced as adjuncts to ongoing therapy with conventional agents with a potential benefit of slowing the progression of type 2 diabetes.

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.

Incretin-based therapy: how do incretin mimetics and DPP-4 inhibitors fit into treatment algorithms for type 2 diabetic patients?

Incretin-based antidiabetic medications have been approved for clinical use for approximately two to three years. While their major clinical characteristics have been known from clinical trials, the discussion now focuses on the best clinical use of GLP-1 receptor agonists (incretin mimetics) and inhibitors of the protease dipeptidyl peptidase-4 (DPP-4). Any novel drug will not fully disclose its spectrum of beneficial and adverse activity before long-term trials with clinical endpoints are available. This, typically, will last 5-8 years. Nevertheless, there are convincing reasons to use incretin mimetics and DPP-4 inhibitors even in the absence of such results. This decision should be based on specific patient characteristics and (expected) treatment results, in comparison to other available treatment options. The present manuscript tries to describe the current state-of-the-art of using incretin mimetics and DPP-4 inhibitors in clinical practice, including an attempt to suggest their place in treatment algorithms for type 2-diabetic patients.

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.

An Update of Recent Trials with Vildagliptin, a Dipeptidyl Peptidase-4 Inhibitor for the Treatment of Type 2 Diabetes

Objective:

To review the clinical efficacy and tolerability of vildagliptin, a dipeptidyl peptidase-4 (DPP-4) inhibitor, for the treatment of type 2 diabetes, based on recent Phase 3 trials.

Data Sources:

Primary literature and review articles were obtained via a MEDLINE search (2005–November 2007) using the search terms diabetes, vildagliptin, and LAF-237. Additional data from abstracts presented at clinical meetings were included when appropriate.

Study Selection:

Nine double-blind, randomized, multicenter, parallel-group trials and vildagliptin studies were identified and reviewed.

Data Synthesis:

Vildagliptin, a selective DPP-4 inhibitor, has been shown to produce clinically significant reductions in hemoglobin A1c (A1C) levels when used as monotherapy (0.6–1%) or in combination with other glucose-lowering agents (mean decrease 0.7%). Phase 3 trials indicated a 24- to 52-week sustained effect on reduction of blood glucose in patients with type 2 diabetes. The primary endpoint for all trials was change from baseline A1C. In the intent-to-treat population, baseline A1C was compared with end-of-study A1C. More than 2,500 patients with type 2 diabetes enrolled in monotherapy trials; an additional 2,119 participated in combination therapy trials. Males outnumbered females, and all groups included obese patients. The most common adverse effects reported were nasopharyngitis, headache, and dizziness. Vildagliptin was weight-neutral and produced a rate of hypoglycemia similar to that of placebo.

Conclusions:

Vildagliptin appears to be a promising agent for the management of type 2 diabetes.

Efficacy and safety of incretin-based therapies in patients with type 2 diabetes mellitus

This article aims to provide an overview of efficacy and safety data on glucagon-like peptide-1 (GLP-1) receptor agonists and dipeptidyl peptidase-4 (DPP-4) inhibitors in the treatment of type 2 diabetes mellitus. Our goal is to differentiate the clinical profiles of GLP-1 receptor agonists and DPP-4 inhibitors, as well as the individual agents within each class. Additionally, we examine the utility of GLP-1 receptor agonists and DPP-4 inhibitors as these agents may be applied at different stages of type 2 diabetes therapy and discuss recently published clinical findings and their implications for treatment.

Unraveling the science of incretin biology

Type 2 diabetes mellitus has become an enormous and worldwide healthcare problem that is almost certain to worsen. Current therapies, which address glycemia and insulin resistance, have not adequately addressed the complications and treatment failures associated with this disease. New treatments based on the incretin hormones provide a novel approach to address some components of the complex pathophysiology of type 2 diabetes. The purpose of this review is to elucidate the science of the incretin hormones and describe the incretin effect and its regulatory role in beta-cell function, insulin secretion, and glucose metabolism. The key endogenous hormones of incretin system are glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1); a key enzymatic regulator of these hormones is dipeptidyl peptidase-4, which rapidly inactivates/degrades the incretin hormones. The roles of the incretin hormones in the regulation of glucose metabolism and other related physiologic processes such as gut motility and food intake are disturbed in type 2 diabetes. These disturbances--defects in the incretin system--contribute to the pathophysiology of type 2 diabetes in manifold ways. Consequently, therapies designed to address impairments to the effects of the incretin hormones have the potential to improve glucose regulation and other abnormalities (e.g., weight gain, loss of beta-cell function) associated with type 2 diabetes.

Unraveling the science of incretin biology

Type 2 diabetes mellitus has become an enormous and worldwide healthcare problem that is almost certain to worsen. Current therapies, which address glycemia and insulin resistance, have not adequately addressed the complications and treatment failures associated with this disease. New treatments based on the incretin hormones provide a novel approach to address some components of the complex pathophysiology of type 2 diabetes. The purpose of this review is to elucidate the science of the incretin hormones and describe the incretin effect and its regulatory role in beta-cell function, insulin secretion, and glucose metabolism. The key endogenous hormones of incretin system are glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1); a key enzymatic regulator of these hormones is dipeptidyl peptidase-4, which rapidly inactivates/degrades the incretin hormones. The roles of the incretin hormones in the regulation of glucose metabolism and other related physiologic processes such as gut motility and food intake are disturbed in type 2 diabetes. These disturbances--defects in the incretin system--contribute to the pathophysiology of type 2 diabetes in manifold ways. Consequently, therapies designed to address impairments to the effects of the incretin hormones have the potential to improve glucose regulation and other abnormalities (e.g., weight gain, loss of beta-cell function) associated with type 2 diabetes.

Efficacy and safety of incretin-based therapies in patients with type 2 diabetes mellitus

This article aims to provide an overview of efficacy and safety data on glucagon-like peptide-1 (GLP-1) receptor agonists and dipeptidyl peptidase-4 (DPP-4) inhibitors in the treatment of type 2 diabetes mellitus. Our goal is to differentiate the clinical profiles of GLP-1 receptor agonists and DPP-4 inhibitors, as well as the individual agents within each class. Additionally, we examine the utility of GLP-1 receptor agonists and DPP-4 inhibitors as these agents may be applied at different stages of type 2 diabetes therapy and discuss recently published clinical findings and their implications for treatment.

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.

The therapeutic role of incretin mimetics and DPP-4 inhibitors

PURPOSE

Gastric inhibitory peptide (GIP) and glucagon-like peptide-1 (GLP-1) stimulate the secretion of insulin when blood glucose levels are elevated and inhibit the postprandial release of glucagon. An increased understanding of the role of these incretin hormones in insulin and blood glucose regulation has resulted in the development of new types of medications for managing diabetes. GLP-1 agonists and dipeptidyl peptidase-IV (DPP-4) inhibitors are 2 classes of medications that have been shown to offer benefits for patients with type 2 diabetes. To use and teach patients how to use these medications effectively, educators need to understand their mechanisms of action, indications and contraindications, side effects, and effectiveness. Expanding the number of options available has increased the complexity of providing care and education, but also offers new opportunities to help our patients achieve better outcomes.

CONCLUSION

This article provides an overview of the physiology of insulin regulation and the roles of GIP, GLP-1, and DPP-4; discusses how the action of incretin hormones is affected by diabetes; and describes the therapeutic agents in these classes and their potential use by people with diabetes.

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.

Islet G protein-coupled receptors as potential targets for treatment of type 2 diabetes

Islet dysfunction - characterized by a combination of defective insulin secretion, inappropriately high glucagon secretion and reduced beta-cell mass - has a central role in the pathophysiology of type 2 diabetes. Several G protein-coupled receptors (GPCRs) expressed in islet beta-cells are known to be involved in the regulation of islet function, and therefore are potential therapeutic targets. This is evident from the recent success of glucagon-like peptide 1 (GLP1) mimetics and dipeptidyl peptidase 4 (DPP4) inhibitors, which promote activation of the GLP1 receptor to stimulate insulin secretion and inhibit glucagon secretion, and also have the potential to increase beta-cell mass. Other islet beta-cell GPCRs that are involved in the regulation of islet function include the glucose-dependent insulinotropic peptide (GIP) receptor, lipid GPCRs, pleiotropic peptide GPCRs and islet biogenic amine GPCRs. This Review summarizes islet GPCR expression, signalling and function, and highlights their potential as targets for the treatment of type 2 diabetes.

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.

DPP4 inhibitors: from sitagliptin monotherapy to the new alogliptin-pioglitazone combination therapy

Diabetes mellitus (DM) is currently considered to be an epidemic disease. A safe and effective treatment has long been sought by scientists. Incretin mimetics and dipeptidyl peptidase-4 (DPP4) inhibitors represent a new class of agents that have recently been included as antidiabetic drugs. Although only a limited number of studies exist regarding the treatment of DM based on the incretin effect, DPP4 inhibitors have so far proved to be safe and effective, both when administered alone or in combination with other antidiabetic medication. This review focuses on incretin-effect physiology, as well as the DPP4 inhibitors, from sitagliptin to the new alogliptin-pioglitazone combination agent, given as monotherapy and in combination with other antidiabetic agents.

Impact of incretin therapy on islet dysfunction: an underlying defect in the pathophysiology of type 2 diabetes

Glucose homeostasis is governed by a complex interplay of hormonal signaling and modulation. Insulin, glucagon, amylin, the incretin hormones glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1), and other hormones and enzymes interact to maintain glucose homeostasis and normal cellular metabolism. Derangements in these hormonal interactions, particularly insulin deficits and impaired insulin action, result in the development of type 2 diabetes-but only in individuals who have experienced significant dysfunction or loss of beta-cells, located in the pancreatic islets of Langerhans. Much less is known about the impact of alpha-cell dysregulation on glucose homeostasis, although it has been demonstrated that glucagon-secreting alpha-cells, also located in the pancreatic islets, play an important role in glucose metabolism. Because beta-cell dysfunction occurs early in the course of type 2 diabetes and is progressive, early intervention with therapies that improve beta-cell function is desirable. In addition to reducing HbA1c and fasting plasma glucose, the recently developed diabetes therapies GLP-1 receptor agonists (eg, exenatide, liraglutide) and dipeptidyl peptidase-4 (DPP-4) inhibitors (eg, sitagliptin, vildagliptin) appear to have beneficial effects on beta-cell dysfunction and, possibly, on alpha-cell dysregulation.

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.

Dipeptidyl peptidase-4 as a new target of action for type 2 diabetes mellitus: a systematic review

Type 2 diabetes mellitus is a metabolic disease leading to microvascular and macrovascular complications including coronary artery disease and stroke. Management of diabetes has been challenging, particularly in the presence of the enormous prevalence of obesity. In recent years, various inhibitors of the enzyme dipeptidyl peptidase (DPP)-4 have been developed to treat diabetes. The enzyme DPP-4 cleaves incretins, which, among other functions, stimulate insulin and suppresses glucagon. Inhibition of this enzyme results in an increase in the half-life and the sustained physiologic action of incretins, leading to an improvement in hyperglycemia. One such agent, namely sitagliptin (MK-04,310), has been introduced into the United States market, and another agent, vildagliptin (LAF237), is being used in Europe and elsewhere. This article is intended to evaluate the effectiveness of DPP-4 inhibitors as a therapeutic modality for managing type 2 diabetes. The authors conducted a literature search of various databases to identify the clinical trials involving the DPP inhibitors and concluded that the DPP-4 inhibitors, for example, sitagliptin and vildagliptin, are efficacious for managing diabetes as monotherapy or combination therapy.

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.

Emerging role of dipeptidyl peptidase-4 inhibitors in the management of type 2 diabetes

BACKGROUND

In type 2 diabetes mellitus (T2DM) there is a progressive loss of beta-cell function. One new approach yielding promising results is the use of the orally active dipeptidyl peptidase-4 (DPP-4) inhibitors. However, every new compound for T2DM has to prove long-term safety especially on cardiovascular outcomes.

OBJECTIVES

Systematic review and meta-analysis of the effects of sitagliptin and vildagliptin therapy on main efficacy parameters and safety. SELECTION CRITERIA, DATA COLLECTION, AND ANALYSIS: Randomized controlled clinical studies of at least 12 weeks' duration in T2DM.

RESULTS

DPP-4 inhibitors versus placebo showed glycosylated hemoglobin A1c (A1c) improvements of 0.7% versus placebo but not compared to monotherapy with other hypoglycemic agents (0.3% in favor of controls). The overall risk profile of DPP-4 inhibitors was low, however a 34% relative risk increase (95% confidence interval 10% to 64%, P = 0.004) was noted for all-cause infection associated with sitagliptin use. No data on immune function, health-related quality of life and diabetic complications could be extracted.

CONCLUSIONS

DPP-4 inhibitors have some theoretical advantages over existing therapies with oral antidiabetic compounds but should currently be restricted to individual patients. Long-term data on cardiovascular outcomes and safety are needed before widespread use of these new agents.

Incretin-based therapies in type 2 diabetes: a review of clinical results

GLP-1 analogues (incretin mimetics) and DPP-4 inhibitors (incretin enhancers) represent new classes of anti-diabetic agents for the treatment of type 2 diabetes. The efficacy and safety of the incretin mimetic exenatide and of the DPP-4 inhibitors, sitagliptin and vildagliptin, have been clearly demonstrated by a very large number of clinical trials. Efficacy was demonstrated in terms of reduction of HbA1c, fasting and postprandial glucose. Moreover, exenatide showed a favourable effect on weight, while DPP-4 inhibitors were neutral with respect to this outcome. The low rate of hypoglycemic events seen in all studies confirms the glucose dependent action of incretins.

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.

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.

Metformin therapy and clinical uses

Metformin is now established as a first-line antidiabetic therapy for the management of type 2 diabetes. Its early use in treatment algorithms is supported by lack of weight gain, low risk of hypoglycaemia and its mode of action to counter insulin resistance. The drug's anti-atherosclerotic and cardioprotective effects have recently been confirmed in prospective and retrospective studies, and appear to reflect a collection of glucose-independent effects on the vascular endothelium, suppressant effects on glycation, oxidative stress and formation of adhesion molecules, stimulation of fibrinolysis and favourable effects on the lipid profile. Although avoidance of troublesome gastrointestinal tolerability issues requires careful dose titration, the risk of serious adverse events is considered low provided that contra-indications (especially with respect to renal function) are observed. As many of its actions go beyond glucose lowering, emerging evidence indicates potential benefits in other insulin-resistant states and possibly tumour suppression.

DPP-4 inhibitors and GLP-1 analogues: for whom? Which place for incretins in the management of type 2 diabetic patients?

This review tries to delineate how to insert the GLP-1 based agents, DPP4-inhibitors (sitagliptin and vildagliptin) and GLP-1 analogues (exenatide and liraglutide), in the guidelines and the daily practice for the management of type 2 diabetes (T2DM). Orally administered DPP-4 inhibitors reduce HbA(1c) by 0.5-1.1%, without hypoglycaemic events and no weight gain. The subcutaneous injected GLP-1 analogues show larger reductions in HbA(1c) by 0.8-1.7% and a weight loss (1.75-3.8 kg) with most gastrointestinal common adverse events contributing to a significant treatment interruption. Regarding the efficacy, the cost and the safety of these drugs they will no challenge the use of metformin as the initial therapy of T2DM. In patients'not tolerating metformin or in older patients, DPP-4 inhibitors seem to be an excellent alternative monotherapy. Several studies argue in favour of the use of DPP-4 inhibitors in combination with metformin as a promising second line treatment. This combination offers advantages when compared to others currently used, particularly if one considers the more stringent guidelines with a higher risk of hypoglycaemic events in patient receiving sulfonylureas and mild hyperglycaemia or weight gain with thiazolidinedione (TZD). Oral triple therapy, metformin + TZD + incretin-based drug, has several theoretical advantages but is not supported by any published trial. Finally, obtaining the acceptance of injections once to twice daily vs. oral administration of OADs will probably remain difficult during the first years of treatment in many patients. Nevertheless a long-acting release exenatide formulation (i.e. once weekly), for subcutaneous injection in patients with type 2 diabetes under development shows promising preliminary results. If confirmed, the use of this new class of drugs should be largely developed from monotherapy to combinations (bitherapy or tritherapy), and even instead of insulin or in association with insulin. The long-term effect of GLP-1 based agents on glycaemic control has not yet been established, and their potential impact on beta-cell function in humans remains an area of active investigation. So, further studies are required and will allow progressively determining the use of incretin-based agents in T2DM treatment strategy. Their efficacy, safety and their cost vs. older strategies, will be really evaluated by physicians in the real daily practice and by large and long term systematic surveys, as recently shown in other therapeutic fields.

Therapeutic approach of type 2 diabetes mellitus with GLP-1 based therapies

The goal of this review is to think about how to incorporate the GLP-1 based agents, represented by the dipeptidyl peptidase-4 (DPP-4) inhibitors or the glucagon-like peptide-1 (GLP-1) analogs, in the guidelines for the management of type 2 diabetes (T2DM). Orally administered DPP-4 inhibitors, such as sitagliptin and vildagliptin, reduce HbA(1c) (absolute values) by 0.5-1.1% (5 to 12%, relative values), with few adverse events and no weight gain. The sub-cutaneous injected GLP-1 analogs show larger reductions in HbA(1c) (0.8-1.7%, absolute values; 9.4-20.0%, relative values), associated with weight loss (1.75-3.8 kg); their most common adverse events are gastrointestinal symptoms which contribute to a substantial treatment interruption. If they do not challenge the use of metformin as the initial therapy of T2DM, several studies argue in favour of the use of DPP-4 inhibitors, either in combination with metformin as the initial treatment or, in add-on therapy to metformin. The advantages of this combination over others currently used are reviewed. In patients not tolerating metformin, DPP-4 inhibitors seem to be an excellent alternative as a monotherapy. As long as oral triple therapy is concerned, the choice for the association metformin + thiazolidinedione + incretin-based drug, has again several theoretical advantages against other triple therapy combinations. Finally, in patients with T2DM inadequately controlled with maximal tolerated oral multi-therapies, GLP-1 agonists are a good alternative to insulin therapy, allowing reaching a better glycaemic control together with a weight loss. However, for patients who do not tolerate GLP-1 agonist treatment, and for those not reaching the HbA(1c) target, insulin will remain necessary, allowing getting a better metabolic control, with few adverse events. The long-term effect of these new agents on glycaemic control has not yet been established, and their potential impact on beta-cell function in humans remains an area of active investigation. So, further studies are needed and will allow progressively refining the use of incretin-based agents in T2DM treatment strategy.