Dipeptidyl peptidase IV inhibitors and the incretin system in type 2 diabetes mellitus

As understanding of type 2 diabetes mellitus pathophysiology expands, treatments continue to evolve and new pharmacologic targets emerge. Patients with type 2 diabetes exhibit deficiencies of the incretin system; thus, methods for increasing insulinotropic hormones have become a popular target for therapy. A new class of oral antidiabetics has emerged-the dipeptidyl peptidase IV (DPP-IV) inhibitors. Unlike conventional oral antidiabetic agents, these agents promote glucose homeostasis through inhibition of DPP-IV, the enzyme responsible for degradation of two key glucoregulatory hormones: glucagon-like peptide-1 (GLP-1), which extends the action of insulin while also suppressing the release of glucagon, and glucose-dependent insulinotropic peptide (GIP). Other proposed mechanisms of action of GLP-1 and thus DPP-IV inhibitors include satiety, increased beta-cell production, and inhibition of apoptosis of beta cells. Clinical studies have evaluated the potential for DPP-IV inhibition to reduce glucagon levels, delay gastric emptying, and stimulate insulin release. The DPP-IV inhibitors appear to have excellent therapeutic potential in the management of type 2 diabetes as monotherapy or in combination with existing agents, such as metformin. Their pharmacokinetic and pharmacodynamic profiles support once-daily dosing, with sustainable reductions in glycosylated hemoglobin levels and relatively few adverse effects. Their distinctive mechanism of action and adverse-event profiles may offer advantages over existing therapies, including low risk for hypoglycemia and possible augmentation of pancreatic beta-cell regeneration.     

Gut peptides in the treatment of diabetes mellitus

It has been known for at least one century that agents secreted from the intestine during meal absorption regulates glucose assimilation. Extensive research during the past three decades has identified two gut hormones, glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic peptide (GIP, also known as gastric inhibitory polypeptide) that are important in postprandial glucose metabolism. Both peptides are incretins; they are secreted during carbohydrate absorption and increase insulin secretion. Since they are potent insulin secretagogues, GIP and GLP-1 have received considerable attention as potential diabetes therapeutics. However, only GLP-1 exerts insulinotropic properties when administered to patients with Type 2 diabetes. Both GLP-1 and GIP are rapidly inactivated in the circulation by the enzyme dipeptidyl peptidase IV (DPP-IV). The application of GLP-1 into clinical practice has been delayed due to the need to develop compounds that overcome this rapid inactivation. Two approaches have been taken to utilise the insulinotropic and glucose-lowering actions of GLP-1 as an antidiabetic agent: the development of DPPIV-resistant analogues and the inhibition of DPP-IV. This review focuses on the physiology of GLP-1 and GIP and the advances that have been made thus far in developing treatments based on these physiological incretins for Type 2 diabetes.     

Gut peptides in the treatment of diabetes mellitus

It has been known for at least one century that agents secreted from the intestine during meal absorption regulates glucose assimilation. Extensive research during the past three decades has identified two gut hormones, glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic peptide (GIP, also known as gastric inhibitory polypeptide) that are important in postprandial glucose metabolism. Both peptides are incretins; they are secreted during carbohydrate absorption and increase insulin secretion. Since they are potent insulin secretagogues, GIP and GLP-1 have received considerable attention as potential diabetes therapeutics. However, only GLP-1 exerts insulinotropic properties when administered to patients with Type 2 diabetes. Both GLP-1 and GIP are rapidly inactivated in the circulation by the enzyme dipeptidyl peptidase IV (DPP-IV). The application of GLP-1 into clinical practice has been delayed due to the need to develop compounds that overcome this rapid inactivation. Two approaches have been taken to utilise the insulinotropic and glucose-lowering actions of GLP-1 as an antidiabetic agent: the development of DPP-IV-resistant analogues and the inhibition of DPP-IV. This review focuses on the physiology of GLP-1 and GIP and the advances that have been made thus far in developing treatments based on these physiological incretins for Type 2 diabetes.     

Current advances and therapeutic potential of agents targeting dipeptidyl peptidases-IV, -II, 8/9 and fibroblast activation protein

Dipeptidyl peptidase-IV (DPP-IV), a serine protease that specifically cleaves the N-terminal dipeptide with a preference for L-proline or L-alanine at the penultimate position, is involved in the degradation of incretin hormones, including glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP). GLP-1 regulates glucose homeostasis by stimulating insulin secretion, inhibiting glucagon release, and delaying gastric emptying. Intravenous GLP-1 has been shown to increase insulin secretion in response to elevated glucose levels and offers therapeutic benefit for patients with type 2 diabetes. However, the therapeutic application of GLP-1 is severely compromised by its lack of oral activity and its rapid degradation by plasma DPP-IV. Consequently, small-molecule DPP-IV inhibitors that could extend the duration of action of GLP-1 and prolong its beneficial effects have been investigated as potential therapeutics for type 2 diabetes. This review summarizes important structural classes of DPP-IV inhibitors, focusing mainly on their inhibitory potency and selectivity for DPP-IV over other related peptidases such as DPP-II, DPP8, DPP9, and FAP. Because inhibition of DPP8 and/or DPP9 has been shown to cause severe toxicity in preclinical species, high selectivity is an important criterion in selecting DPP-IV inhibitors for clinical development. As of today, several DPP-IV inhibitors have completed phase III clinical studies for the treatment of type 2 diabetes. A brief overview of clinical efficacy data on these inhibitor drugs is provided here. In addition, biological activities of other related dipeptidyl peptidases (DPP-II, DPP8, DPP9, and FAP) will be summarized. Selective inhibitors for these peptidases and their therapeutic potential will be discussed.     

Structurally modified analogues of glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) as future antidiabetic agents

Glucagon-like peptide-1(7-36)amide (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) are gastrointestinal insulin-releasing hormones involved in the regulation of postprandial nutrient homeostasis. These two incretin hormones are glucose-dependent stimulators of pancreatic beta-cell function, exhibiting a spectrum of secondary extrapancreatic activities, which favour the efficient control of blood glucose homeostasis. Such actions of GLP-1 and GIP have generated considerable interest in their possible exploitation as novel agents for the treatment of type 2 diabetes. Despite the many attributes of GLP-1 and GIP as possible future antidiabetic agents, their rapid degradation in the circulation by dipeptidyl peptidase IV (DPP IV) to inactive truncated forms GLP-1(9-36)amide and GIP(3-42), severely limits their therapeutic usefulness. This review will consider recent developments in the design and effectiveness of synthetic DPP IV-resistant analogues of GLP-1 and GIP. Consideration will be given to the effects of N-terminal modification and amino acid substitution of GLP-1 and GIP either side of the DPP IV cleavage site on (i) susceptibility to enzymatic degradation, (ii) binding to native hormone receptor, (iii) ability to elevate intracellular cyclic AMP, (iv) potency as insulin secretagogues, and (v) antihyperglycaemic activity in type 2 diabetes. It will be shown that structural modification can produce a varied set of biological activities, ranging from more efficacious analogues to those which antagonise the activity of the native hormone. The antidiabetic properties of the best GLP-1 and GIP analogues indeed promise to provide the basis for novel, effective and long-acting drugs for type 2 diabetes therapy. This approach is currently being pursued actively by the pharmaceutical industry.     

From the bench to the bedside: dipeptidyl peptidase IV inhibitors, a new class of oral antihyperglycemic agents

New therapeutic agents are needed to combat the ever-increasing prevalence of diabetes. The two incretins glucagon-like peptide-1 (7-36) (GLP-1(7-36)) amide and glucose-dependent insulinotropic peptide (GIP) are released from the small intestine in response to the ingestion of nutrients and regulate glucose homeostasis in a glucose-dependent fashion; however, the action of both incretins is terminated by the rapid N-terminal cleavage of two amino acid residues of GLP-1 and GIP by dipeptidyl peptidase-IV (DPP-IV). The preservation of active GLP-1 and GIP by inhibiting DPP-IV activity is an attractive strategy for the treatment of diabetes in patients who exhibit a reduced incretin response. This strategy has resulted in the launch of two DPP-IV inhibitor drugs; sitagliptin in North America, several European territories, and various other countries, and vildagliptin in the EU as well as various countries. This article provides an overview of the recent advances in and the lessons learned from the design of potent and selective small-molecule inhibitors of DPP-IV for the treatment of type 2 diabetes.     

Inhibitors of dipeptidyl peptidase IV--recent advances and structural views

Prevalence of type 2 diabetes has increased dramatically in the last decades. Current medicines are not yet capable to efficiently prevent or reverse progression of the disease and its associated comorbidities. As a consequence, there is a great need for novel antidiabetic drugs. Treatments of type 2 diabetes that are based on enhanced and sustained action of insulinotropic incretin hormones such as GLP-1 have received much attention in the past years. Treatment strategies include administration of: 1) GLP-1 analogues that are resistant to degradation by the serine protease DPP-IV, and 2) small molecule DPP-IV inhibitors that are able to provide sustained action of endogenous GLP-1, again by preventing its degradation. This review summarizes recent research results for the second approach. It briefly touches upon the advantages that treatment of type 2 diabetes with DPP-IV inhibitors may offer over current medications. In the main section, several important structural classes of DPP-IV inhibitors are described and compared based on literature data. Specific attention is given to the analysis of several X-ray structures of enzyme-inhibitor co-crystals. Finally, as clinical data are steadily emerging for some of the most advanced development candidates, the last section of this review is providing a brief overview of some efficacy data from recent clinical studies with DPP-IV inhibitors.     

Sitagliptin: Profile of a novel DPP-4 inhibitor for the treatment of type 2 diabetes

Novel therapeutic strategies for type 2 diabetes are needed, since the current treatment options neither address all pathophysiological mechanisms nor achieve the glycemic target goals. A general islet-cell dysfunction including insulin- and glucagon-secretion defects contributes to the pathophysiology of type 2 diabetes. Improving islet function by incretin hormone action is a novel therapeutic approach. Glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic peptide (GIP) are important incretin hormones contributing to 50-70% of the stimulation of insulin secretion after a meal. Dipeptidyl-peptidase IV (DPP-4) inhibitors inhibit the degradation of GLP-1 and GIP as well as that of other regulatory peptides. Sitagliptin, a DPP-4 inhibitor, is orally active and has been shown to be efficacious and safe in clinical studies. Sitagliptin has received approval in Mexico, the United States and other countries. Like other DPP-4 inhibitors, sitagliptin reduces hemoglobin A1c (HbA1c), fasting and postprandial glucose by glucose-dependent stimulation of insulin secretion and inhibition of glucagon secretion. Sitagliptin is weight neutral. Indirect measures show a possible improvement of beta-cell function. Sitagliptin does not cause a higher rate of hypoglycemia in comparison to metformin or placebo. This article gives an overview of the mechanisms of action, pharmacology and clinical trial results of sitagliptin.     

Sitagliptin: profile of a novel DPP-4 inhibitor for the treatment of type 2 diabetes (update)

Novel therapeutic strategies for type 2 diabetes are needed, since the current treatment options neither address all pathophysiological mechanisms nor achieve the glycemic target goals. A general islet-cell dysfunction including insulin- and glucagon-secretion defects contributes to the pathophysiology of type 2 diabetes. Improving islet function by incretin hormone action is a novel therapeutic approach. Glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic peptide (GIP) are important incretin hormones contributing to 50-70% of the stimulation of insulin secretion after a meal. Dipeptidyl-peptidase IV (DPP-4) inhibitors inhibit the degradation of GLP-1 and GIP as well as that of other regulatory peptides. Sitagliptin, a DPP-4 inhibitor, is orally active and has been shown to be efficacious and safe in clinical studies. Sitagliptin has received approval in Mexico, the United States and other countries. Like other DPP-4 inhibitors, sitagliptin reduces hemoglobin A1c (HbA1c), fasting and postprandial glucose by glucose-dependent stimulation of insulin secretion and inhibition of glucagon secretion. Sitagliptin is weight neutral. Indirect measures show a possible improvement of beta-cell function. Sitagliptin does not cause a higher rate of hypoglycemia in comparison to metformin or placebo. This article gives an overview of the mechanisms of action, pharmacology and clinical trial results of sitagliptin.     

新型糖尿病治疗药物二肽基肽酶IV抑制药的研究进展

二肽基肽酶IV(DPP-IV)抑制药是治疗2型糖尿病的一类新型口服降糖药。DPP-IV抑制药能抑制DDP-IV活性,从而减少胰高糖素样肽1(GLP-1)、葡萄糖依赖性促胰岛素肽(GIP)等的降解,并在GLP-1及GIP的作用下,促进胰岛素的分泌,在有效降低血糖的同时还具有保护胰岛β细胞的功能。本文就该类药物的研究现状及应用前景进行综述。     

Replacing SUs with incretin-based therapies for type 2 diabetes mellitus: challenges and feasibility

Type 2 diabetes mellitus (T2DM) is a progressive disease characterized by insulin resistance, a steady decline in glucose-induced insulin secretion (most likely caused by a progressive decrease in functional beta-cell mass), and inappropriately regulated glucagon secretion; in combination, these effects result in hyperglycemia. In 1958, sulfonylurea (SU) was introduced to the market as one of the first oral treatments for T2DM. Since then, the ability of SU to stimulate the release of insulin from pancreatic beta-cells by the closure of ATP-sensitive K+-channels has been employed as one of the most widespread treatment options for T2DM. However, SUs are associated with weight gain and a risk of hypoglycemia, and the one-track antidiabetic mechanism of SUs often results in patients being treated with additional antidiabetic drugs. In recent studies, SU has proven to be associated with increased beta-cell apoptosis, suggesting that SU may actually accelerate the progressive decrease in beta-cell mass, thereby promoting the need for insulin replacement. In contrast, the newly developed incretin-based therapies for T2DM employ the beta-cell-preserving properties of incretin hormones - glucagon-like peptide 1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP). More importantly, incretin-based therapies potentiate glucose-stimulated insulin secretion and may restore reduced glucose-induced insulin secretion in T2DM. Furthermore, the insulinotropic effects of GLP-1 and GIP are glucose-dependent, reducing the risk of hypoglycemia. GLP-1 inhibits glucagon secretion and decreases gastrointestinal motility, in turn reducing food intake and body weight. This feature review focuses on the challenges and feasibilities of replacing SU with incretin-based therapy in patients with T2DM.     

Glucagon like peptides-1 modulators as newer target for diabetes

Diabetes mellitus (DM) has been recognized as a growing world-wide epidemic by many health advocacy groups including the World Health Organization (WHO). DM affects about 6% of the North American population. A recent report estimated that 8.2% of adult population worldwide has impaired glucose tolerance. Current treatment approaches include diet, exercise, and a variety of pharmacological agents including insulin, biguanides, sulfonylureas and thiazolidinediones. New therapies are still needed to control metabolic abnormalities, and also to preserve beta-cell mass and to prevent loss of beta-cell function. In many cases monotherapy gradually fails to improve blood glucose control and combination therapy is employed. The long-term success of these treatments varies substantially. Thus, there is an imperative need for novel therapeutic approaches for glycemic control that can complement existing therapies and possibly attempt to preserve normal physiological response to meal intake. Glucagon-like peptide 1 (GLP-1) is a drug candidate which potentially fulfils these conditions. Glucoregulatory actions of GLP-1 include glucose-dependent enhancement of insulin secretion, inhibition of glucagon secretion, slowing of gastric emptying and reduction of food intake. GLP-1 is rapidly inactivated by amino peptidase, Dipeptidyl Peptidase-IV (DPP-IV) and the utility of DPP-IV inhibitors are also under investigation. There is a recent upsurge in the development of GLP-1 mimetics and DPP-IV inhibitors as potential antidiabetic agents. The present review summarizes the concepts of GLP-1 based therapy for type 2 diabetes and the current preclinical and clinical development in GLP-1 modulators.     

DPP-4 inhibitors in diabetic complications: role of DPP-4 beyond glucose control

Dipeptidyl peptidase-4 (DPP-4) inhibitors (gliptins) are an emerging class of antidiabetic drugs that constitutes approximately fifty percent of the market share of the oral hypoglycemic drugs. Its mechanism of action for lowering blood glucose is essentially via inhibition of the rapid degradation of incretin hormones, such as glucagon-like peptide (GLP)-1 and gastric inhibitory polypeptide (GIP), thus the plasma concentration of GLP-1 increases, which promotes insulin secretion from the pancreatic β cells and suppresses glucagon secretion from the α cells. In addition to the direct actions on the pancreas, GLP-1 exhibits diverse actions on different tissues through its action on GLP-1 receptor, which is expressed ubiquitously. Moreover, DPP-4 has multiple substrates besides GLP-1 and GIP, including cytokines, chemokines, neuropeptides, and growth factors, which are involved in many pathophysiological conditions. Recently, it was suggested that DPP-4 is a new adipokine secreted from the adipose tissue, which plays an important role in the regulation of the endocrine function in obesity-associated type 2 diabetes. Consequently, DPP-4 inhibitors have been reported to exhibit cytoprotective functions against various diabetic complications affecting the liver, heart, kidneys, retina, and neurons. This review outlines the current understanding of the effect of DPP-4 inhibitors on the complications associated with type 2 diabetes, such as liver steatosis and inflammation, dysfunction of the adipose tissue and pancreas, cardiovascular diseases, nephropathy, and neuropathy in preclinical and clinical studies.     

Treatment of type 2 diabetes mellitus with agonists of the GLP-1 receptor or DPP-IV inhibitors

Glucagon-like peptide-1 (GLP-1) is a peptide hormone from the gut that stimulates insulin secretion and protects beta-cells, inhibits glucagon secretion and gastric emptying, and reduces appetite and food intake. In agreement with these actions, it has been shown to be highly effective in the treatment of Type 2 diabetes, causing marked improvements in glycaemic profile, insulin sensitivity and beta-cell performance, as well as weight reduction. The hormone is metabolised rapidly by the enzyme dipeptidyl peptidase IV (DPP-IV) and, therefore, cannot be easily used clinically. Instead, resistant analogues of the hormone (or agonists of the GLP-1 receptor) are in development, along with DPP-IV inhibitors, which have been demonstrated to protect the endogenous hormone and enhance its activity. Agonists include both albumin-bound analogues of GLP-1 and exendin-4, a lizard peptide. Clinical studies with exendin have been carried out for > 6 months and have indicated efficacy in patients inadequately treated with oral antidiabetic agents. Orally active DPP-IV inhibitors, suitable for once-daily administration, have demonstrated similar efficacy. Diabetes therapy, based on GLP-1 receptor activation, therefore, appears very promising.     

Dipeptide boronic acid inhibitors of dipeptidyl peptidase IV: determinants of potency and in vivo efficacy and safety

Dipeptidyl peptidase IV (DPP-IV; E.C. 3.4.14.5), a serine protease that degrades the incretin hormones GLP-1 and GIP, is now a validated target for the treatment of type 2 diabetes. Dipeptide boronic acids, among the first, and still among the most potent DPP-IV inhibitors known, suffer from a concern over their safety. Here we evaluate the potency, in vivo efficacy, and safety of a selected set of these inhibitors. The adverse effects induced by boronic acid-based DPP-IV inhibitors are essentially limited to what has been observed previously for non-boronic acid inhibitors and attributed to cross-reactivity with DPP8/9. While consistent with the DPP8/9 hypothesis, they are also consistent with cross-reactivity with some other intracellular target. The results further show that the potency of simple dipeptide boronic acid-based inhibitors can be combined with selectivity against DPP8/9 in vivo to produce agents with a relatively wide therapeutic index (>500) in rodents.     

治疗2型糖尿病药物研究新进展

目的介绍近年来应用于2型糖尿病的新型药物GLP-1类似物、DPP-IV阻断剂及作用于ECS的药物。方法归纳总结国外相关文献,介绍其作用机制、临床实践、不良反应、权威使用指南。结果与结论此类药物具有一定应用前景,但仍存在较多问题,需要进一步探讨和研究。     

ASP8497 is a novel selective and competitive dipeptidyl peptidase-IV inhibitor with antihyperglycemic activity

Dipeptidyl peptidase (DPP)-IV inhibitors are expected to become a useful new class of antidiabetic agent. The aim of the present study is to characterize the in vitro and in vivo profile of ASP8497, (2S,4S)-4-fluoro-1-({[4-methyl-1-(methylsulfonyl)piperidin-4-yl]amino}acetyl)pyrrolidine-2-carbonitrile monofumarate, which is a novel DPP-IV inhibitor. ASP8497 inhibited DPP-IV in plasma from mice, rats, dogs and humans with IC(50) values of 3.86, 2.36, 5.53 and 5.30 nM, respectively. In contrast, ASP8497 did not potently inhibit DPP8 or DPP9 activity (IC(50)>200 nM). Kinetic analysis indicated that ASP8497 inhibits DPP-IV activity in a competitive manner. In streptozotocin-nicotinamide-induced diabetic mice, ASP8497 (3 mg/kg) significantly reduced glucose excursion during the oral glucose tolerance test conducted 0.5 and 8.5 h after administration, with increases in plasma insulin and active glucagon-like peptide-1 (GLP-1) levels. In contrast, ASP8497 (3 and 30 mg/kg) did not cause hypoglycemia in fasted normal mice. Furthermore, administration of exogenous GLP-1 induced significant inhibition of gastric emptying and small intestinal transit rates, but ASP8497 (30 mg/kg) had no significant effects in normal mice. These present preclinical studies indicate that ASP8497 is a novel selective DPP-IV inhibitor with long-acting antidiabetic effect that might be a potential agent for type 2 diabetes.     

Sitagliptin with metformin: profile of a combination for the treatment of type 2 diabetes

Sitagliptin, a novel orally-active dipeptidyl-peptidase (DPP-4) inhibitor has been introduced into type 2 diabetes therapy. Sitagliptin inhibits the degradation of glucagon-like peptide-1 (GLP-1) and gastric inhibitory polypeptide (GIP), as well as that of other regulatory peptides important for glucose homeostasis. It reduces haemoglobin A1c (HbA1c), fasting and postprandial glucose by glucose- dependent stimulation of insulin secretion and inhibition of glucagon secretion. Sitagliptin is weight neutral. Indirect measures show a possible improvement of beta-cell function. Sitagliptin does not cause hypoglycemia when compared to metformin or placebo. Metformin, which has a different unique mechanism, has been used in type 2 diabetes for approximately 50 years. Metformin improves insulin resistance and is the first-line antidiabetic drug in use today. The combination of a DPP-4 inhibitor with metformin allows a broad and complementary spectrum of antidiabetic actions. This combination does not increase the risk of hypoglycaemia nor does it promote weight gain, an adverse effect of various other oral antidiabetic combinations. This article gives an overview of the data available on the combined antidiabetic effects of metformin and sitagliptin.     

Inhibition of DPP-4: a new therapeutic approach for the treatment of type 2 diabetes

ABSTRACT

Background: Glucagon-like peptide-1 (GLP?1) and glucose-dependent insulinotropic polypeptide (GIP) are hormones secreted by the enteroendocrine cells of the gut in response to the ingestion of nutrients. These incretin hormones, so called because they increase insulin secretion, are key modulators of pancreatic islet hormone secretion and, thus, glucose homeostasis. The glucoregulatory effects of incretins are the basis for new therapies currently being developed for the treatment of type 2 diabetes mellitus (T2DM). Drugs that inhibit dipeptidyl peptidase-4 (DPP?4), a ubiquitous enzyme that rapidly inactivates both GLP-1 and GIP, increase active levels of these hormones and, in doing so, improve islet function and glycemic control in T2DM.

Scope: In this review, we briefly describe (1) the role of pancreatic islet dysfunction in the onset and progression of T2DM, (2) the rationale for developing drugs that enhance incretin activity, (3) the evidence that inhibition of DPP?4 is effective in ameliorating islet dysfunction and improving glycemic control in T2DM, (4) the efficacy, safety, and tolerability of DPP?4 inhibitors as monotherapy and in combination with other antidiabetic agents, and (5) the potential utility of DPP?4 inhibitors relative to existing oral antidiabetic agents and newer antidiabetic drugs in the pipeline. The review is based upon MEDLINE literature searches (1966–August 2006) and abstracts and presentations from the American Diabetes Association Scientific Sessions (2002–2006) and the European Association for the Study of Diabetes Annual Meetings (1998–2006). Basic science, preclinical, and clinical studies and review articles published in the English language were evaluated and selected based upon consideration of their originality, relevance, and frequency of citation.

Findings: DPP?4 inhibitors are a new class of antidiabetogenic drugs that provide comparable efficacy to current treatments. They are effective as monotherapy in patients inadequately controlled with diet and exercise and as add-on therapy in combination with metformin, thiazolidinediones, and insulin. The DPP?4 inhibitors are well tolerated, carry a low risk of producing hypoglycemia, and are weight-neutral. The long-term durability of effect on glycemic control and β?cell morphology and function remain to be established.

Conclusions: Islet cell dysfunction is central to the pathogenesis of T2DM. Incretin-based therapies, including GLP-1 analogues and DPP?4 inhibitors, have been shown to restore glucose homeostasis and improve glycemic control. The DPP?4 inhibitors, which can be used as monotherapy or in combination with other antidiabetic drugs, are a promising new treatment option, especially for patients with early-stage T2DM and more severe hyperglycemia.     

Computational studies on structurally diverse dipeptidyl peptidase IV inhibitors: an approach for new antidiabetic drug development

Dipeptidyl peptidase IV (DPP-IV) deactivates the natural hypoglycemic incretin hormone GLP-1. Inhibition of this enzyme restores glucose homeostasis in diabetic patients making it an attractive target for the development of new antidiabetic drugs. With this in mind, we suggested an in silico work flow for the identification of novel DPP-IV inhibitors. Ligand-based and structure-based pharmacophores were designed using HipHop program provided in catalyst and ligandScout 3.0 software, respectively. Generated models were validated by receiver operating characteristic curve analysis, Guner–Henry scoring method and by pharmacophore-based screening of marketed DPP-IV inhibitors. Ligand-based pharmacophore model A scored 0.8 AUC value, 0.865 Guner–Henry score and gave all marketed DPP-IV inhibitors as hits through screening while structure-based pharmacophore B scored 0.77 AUC value, 0.66 Guner–Henry score and gave four marketed DPP-IV inhibitors as hits (except alogliptin) out of five. These validated pharmacophores have effectively been used in search of three databases, Maybridge hitfinder collection, Chemdiv, and Asinex. Resulting hits were subjected to molecular docking using ligandfit program. Five hit compounds namely Asinex ASN 09417841, AW 00785, ChemDiv 0173-0023, ChemDiv 0276-0112, and ChemDiv 8010-1357 scored high Ligscore1 and ?PLP1 score comparable to standard drug sitagliptin. Good interactions were found with important residues like Glu205, Glu206, Tyr662, Phe357, Arg358, Tyr666 etc. They were reported as novel virtual leads to design potent DPP-IV inhibitors.