Studies on antidiabetic agents. I. Synthesis of 5-[4-(2-methyl-2-phenylpropoxy)-benzyl]thiazolidine-2,4-dione (AL-321) and related compounds

Is Target-Based Drug Discovery Efficient? Discovery and "Off-Target" Mechanisms of All Drugs

Target-based drug discovery is the dominant paradigm of drug discovery; however, a comprehensive evaluation of its real-world efficiency is lacking. Here, a manual systematic review of about 32000 articles and patents dating back to 150 years ago demonstrates its apparent inefficiency. Analyzing the origins of all approved drugs reveals that, despite several decades of dominance, only 9.4% of small-molecule drugs have been discovered through "target-based" assays. Moreover, the therapeutic effects of even this minimal share cannot be solely attributed and reduced to their purported targets, as they depend on numerous off-target mechanisms unconsciously incorporated by phenotypic observations. The data suggest that reductionist target-based drug discovery may be a cause of the productivity crisis in drug discovery. An evidence-based approach to enhance efficiency seems to be prioritizing, in selecting and optimizing molecules, higher-level phenotypic observations that are closer to the sought-after therapeutic effects using tools like artificial intelligence and machine learning.

Synthesis, Anticancer, and Antibacterial Studies of Benzylidene Bearing 5-substituted and 3,5-disubstituted-2,4-Thiazolidinedione Derivatives

AIM

To develop novel compounds having potent anticancer and antibacterial activities.

BACKGROUND

Several studies have proved that benzylidene analogues of clinical 2,4-TZDs, such as troglitazone and ciglitazone, have more potent antiproliferative activity than their parent compounds. Literature studies also revealed that the attachment of more heterocyclic rings, containing nitrogen on 5th position of 2,4-TZD, can enhance the antimicrobial activity. Hence, attachment of various moieties on the benzylidene ring may produce safe and effective compounds in the future.

OBJECTIVE

The objective of the present study was to synthesize a set of novel benzylidene ring containing 5- and 3-substituted-2,4-thiazolidinedione derivatives and evaluate them for their anticancer and antibacterial activity.

METHODS

The synthesized compounds were characterized by IR, NMR, mass, and elemental studies. The in vitro cytotoxicity studies were performed for human breast cancer (MCF-7) and human lung cancer (A549) cells and HepG2 cell-line and compared to standard drug doxorubicin by MTT assay. Antimicrobial activity of the synthesized 2,4-thiazolidinediones derivatives was carried out using the cup plate method with slight modification.

RESULTS

The results obtained showed that TZ-5 and TZ-13 exhibited good antiproliferative activity against A549 cancer cell-line, whereas TZ-10 exhibited moderate antiproliferative activity against HepG2 cell-line when compared to standard drug doxorubicin. TZ-5 also exhibited reasonable activity against the MCF-7 cell-line with doxorubicin as standard. TZ-4, TZ-5, TZ-6, TZ-7, and TZ- 16 exhibited remarkable antibacterial activity against Gram positive and moderate activity against Gram negative bacteria with the standard drug ciprofloxacin.

CONCLUSION

Attachment of heterocyclic rings containing nitrogen as the hetero atom improves the anticancer and antimicrobial potential. Attachment of electronegative elements like halogens can also enhance the antimicrobial activity. Further structure modifications may lead to the development of more potent 2,4-TZD leads that can be evaluated for further advanced studies.

Peroxisome proliferator-activated receptor agonists and antagonists: a patent review (2014-present)

Introduction: Peroxisome proliferator-activated receptors (PPARs), PPARα, PPARδ, and PPARγ, play an important role in the regulation of various physiological processes, specifically lipid and energy metabolism and immunity. PPARα agonists (fibrates) and PPARγ agonists (thiazolidinediones) are used for the treatment of hypertriglyceridemia and type 2 diabetes, respectively. PPARδ activation enhances mitochondrial and energy metabolism but PPARδ-acting drugs are not yet available. Many synthetic ligands for PPARs have been developed to expand their therapeutic applications.Areas covered: The authors searched recent patent activity regarding PPAR ligands. Novel PPARα agonists, PPARδ agonists, PPARγ agonists, PPARα/γ dual agonists, and PPARγ antagonists have been claimed for the treatment of metabolic disease and inflammatory disease. Methods for the combination of PPAR ligands with other drugs and expanded application of PPAR agonists for bone and neurological disease have been also claimed.Expert opinion: Novel PPAR ligands and the combination of PPAR ligands with other drugs have been claimed for the treatment of mitochondrial disease, inflammatory/autoimmune disease, neurological disease, and cancer in addition to metabolic diseases including dyslipidemia and type 2 diabetes. Selective therapeutic actions of PPAR ligands should be exploited to avoid adverse effects. More basic studies are needed to elucidate the molecular mechanisms of selective actions.

Diversity-oriented synthesis of spirothiazolidinediones and their biological evaluation

We report a new synthetic approach to assemble spirothiazolidinediones via a [2 + 2 + 2] cyclotrimerization reaction and the derivatives were further functionalized through DA chemistry and click reaction. Using flow cytometry, it was shown for the first time that the new benzyl alcohol derivatives of thiazolidine-2,4-dione generated here are efficient apoptosis inducers in the HeLa, Hek293, U937, Jurkat, and K562 cell lines.

Synthesis, biological evaluation and molecular docking studies of novel 3,5-disubstituted 2,4-thiazolidinediones derivatives

A series of thirteen novel 2,4-thiazolidinedione derivatives were synthesized through three step reaction procedure. The title compounds were synthesized by Knoevenagel condensation at the 5th position of the 2,4-thiazolidinedione ring. Various physicochemical and spectral studies were conducted to characterize the synthesized derivatives including- IR, Mass, ¹H NMR, ¹³C NMR and elemental analysis. The derivatives were screened for in vivo anti diabetic, in vivo anti-inflammatory and in vitro free radical scavenging activities by carrageenan induced rat paw edema method, alloxan induced diabetes in wistar rats method and FRAP (ferric reducing antioxidant power) method respectively. Some of the derivatives emerged out as potent antidiabetic, anti inflammatory and free radical scavenging agents. Molecular docking was carried out to investigate some possible structural insights into the potential binding patterns of the most potent anti-diabetic molecules NB7,NB12 and NB13 with the active sites of target PPARγ (PDB ID: 2PRG) using MOE software. Dichloro derivative compound NB-7 has shown great potential in the present study as it not only has maximum antidiabetic activity but also possess excellent anti-inflammatory and antioxidant potential.

The Pioglitazone Trek via Human PPAR Gamma: From Discovery to a Medicine at the FDA and Beyond

For almost two decades, pioglitazone has been prescribed primarily to prevent and treat insulin resistance in some type 2 diabetic patients. In this review, we trace the path to discovery of pioglitazone as a thiazolidinedione compound, the glitazone tracks through the regulatory agencies, the trek to molecular agonism in the nucleus and the binding of pioglitazone to the nuclear receptor PPAR gamma. Given the rise in consumption of pioglitazone in T2D patients worldwide and the increased number of clinical trials currently testing alternate medical uses for this drug, there is also merit to some reflection on the reported adverse effects. Going forward, it is imperative to continue investigations into the mechanisms of actions of pioglitazone, the potential of glitazone drugs to contribute to unmet needs in complex diseases associated with the dynamics of adaptive homeostasis, and also the routes to minimizing adverse effects in every-day patients throughout the world.

DFT approach to (benzylthio)acetic acid: Conformational search, molecular (monomer and dimer) structure, vibrational spectroscopy and some electronic properties

The DFT studies were carried out with the B3LYP method utilizing the 6-31G and 6-311++G(d,p) basis sets depending on whether the aim of calculations was to gain the geometry at equilibrium, or to calculate the optimized molecular structure of (benzylthio)acetic acid (Hbta) in the forms of monomer and dimer. The minimum conformational energy search was followed by the potential energy surface (PES) scan of all rotary bonds existing in the acid molecule. The optimized geometrical monomeric and dimeric structures of the title compound were compared with the experimental structural data in the solid state. The detailed vibrational interpretation of experimental infrared and Raman bands was performed on the basis of theoretically simulated ESFF-scaled wavenumbers calculated for the monomer and dimer structures of Hbta. The electronic characteristics of Hbta is also presented in terms of Mulliken atomic charges, frontier molecular orbitals and global reactivity descriptors. Additionally, the MEP and ESP surfaces were computed to predict coordination sites for potential metal complex formation.

G Protein-coupled Receptor 40 (GPR40) and Peroxisome Proliferator-activated Receptor γ (PPARγ): AN INTEGRATED TWO-RECEPTOR SIGNALING PATHWAY

Peroxisome proliferator-activated receptor γ (PPARγ) ligands have been widely used to treat type 2 diabetes mellitus. However, knowledge of PPARγ signaling remains incomplete. In addition to PPARγ, these drugs also activate G protein-coupled receptor 40 (GPR40), a Gαq-coupled free fatty acid receptor linked to MAPK networks and glucose homeostasis. Notably, p38 MAPK activation has been implicated in PPARγ signaling. Here, rosiglitazone (RGZ) activation of GPR40 and p38 MAPK was found to boost PPARγ-induced gene transcription in human endothelium. Inhibition or knockdown of p38 MAPK or expression of a dominant negative (DN) p38 MAPK mutant blunted RGZ-induced PPARγ DNA binding and reporter activity in EA.hy926 human endothelial cells. GPR40 inhibition or knockdown, or expression of a DN-Gαq mutant likewise blocked activation of both p38 MAPK and PPARγ reporters. Importantly, RGZ induction of PPARγ target genes in primary human pulmonary artery endothelial cells (PAECs) was suppressed by knockdown of either p38 MAPK or GPR40. GPR40/PPARγ signal transduction was dependent on p38 MAPK activation and induction of PPARγ co-activator-1 (PGC1α). Silencing of p38 MAPK or GPR40 abolished the ability of RGZ to induce phosphorylation and expression of PGC1α in PAECs. Knockdown of PGC1α, its essential activator SIRT1, or its binding partner/co-activator EP300 inhibited RGZ induction of PPARγ-regulated genes in PAECs. RGZ/GPR40/p38 MAPK signaling also led to EP300 phosphorylation, an event that enhances PPARγ target gene transcription. Thus, GPR40 and PPARγ can function as an integrated two-receptor signal transduction pathway, a finding with implications for rational drug development.

Thiazolidine-2,4-diones: progress towards multifarious applications

The promising activity shown by compounds containing thiazolidine-2,4-dione nucleus in numerous categories such as anti-hyperglycaemics, aldose reductase inhibitors, anti-cancer, anti-inflammatory, anti-arthritics, anti-microbials, etc. has made it an indispensable anchor for development of new therapeutic agents. Varied substituents on the thiazolidine-2,4-dione nucleus have provided a wide spectrum of biological activities. Importance of this nucleus in some activities like, peroxisome proliferator activated receptor γ (PPARγ) agonism and PPARγ-dependent and -independent anti-cancer activities are reviewed separately in literature. Short reviews on biological importance of this nucleus are also known in literature. However, owing to fast development of new drugs possessing thiazolidine-2,4-dione nucleus many research reports are generated in short span of time. So, there is a need to couple the latest information with the earlier information to understand the current status of thiazolidine-2,4-dione nucleus in medicinal chemistry research. In the present review, various derivatives of thiazolidine-2,4-diones with different pharmacological activities are described on the basis of substitution pattern around the nucleus combined with the docking studies performed in the active site of the corresponding receptors with an aim to help medicinal chemists for developing an SAR on thiazolidine-2,4-dione derived compounds for each activity. This discussion will further help in the development of novel thiazolidine-2,4-dione compounds.

Synthesis and pharmacological investigation of 2-(4-dimethylaminophenyl)-3,5-disubstituted thiazolidin-4-ones as anticonvulsants

A new series of 2-(4-dimethylaminophenyl)-3-substituted thiazolidin-4-one-5-yl-acetyl acetamides/benzamides were synthesized by the nucleophilic substitution of 3-substituted-2-(4-dimethylaminophenyl)-thiazolidin-4-one-5-yl-acetylchloride with acetamide and benzamide. The starting material 3-substituted-2-(4-dimethylaminophenyl)-thiazolidin-4-one-5-yl-acetylchloride was synthesized from 3-substituted-2-(4-dimethylaminophenyl)-thiazolidin-4-one-5-yl-acetic acid, which in turn was prepared by one-pot reaction of amino component, p-dimethylamino benzaldehyde and mercapto succinic acid. The title compounds were investigated for their anticonvulsant activities; among the test compounds, compound 2-(4-dimethylaminophenyl)-3-phenylamino-thiazolidine-4-one-5-yl-acetylbenzamide (14) emerged as the most active compound of the series and as moderately more potent than the reference standard diazepam.

Cellular responses to the metal-binding properties of metformin

In recent decades, the antihyperglycemic biguanide metformin has been used extensively in the treatment of type 2 diabetes, despite continuing uncertainty over its direct target. In this article, using two independent approaches, we demonstrate that cellular actions of metformin are disrupted by interference with its metal-binding properties, which have been known for over a century but little studied by biologists. We demonstrate that copper sequestration opposes known actions of metformin not only on AMP-activated protein kinase (AMPK)-dependent signaling, but also on S6 protein phosphorylation. Biguanide/metal interactions are stabilized by extensive π-electron delocalization and by investigating analogs of metformin; we provide evidence that this intrinsic property enables biguanides to regulate AMPK, glucose production, gluconeogenic gene expression, mitochondrial respiration, and mitochondrial copper binding. In contrast, regulation of S6 phosphorylation is prevented only by direct modification of the metal-liganding groups of the biguanide structure, supporting recent data that AMPK and S6 phosphorylation are regulated independently by biguanides. Additional studies with pioglitazone suggest that mitochondrial copper is targeted by both of these clinically important drugs. Together, these results suggest that cellular effects of biguanides depend on their metal-binding properties. This link may illuminate a better understanding of the molecular mechanisms enabling antihyperglycemic drug action.

Peroxisome Proliferators-Activated Receptor (PPAR) Modulators and Metabolic Disorders

Overweight and obesity lead to an increased risk for metabolic disorders such as impaired glucose regulation/insulin resistance, dyslipidemia, and hypertension. Several molecular drug targets with potential to prevent or treat metabolic disorders have been revealed. Interestingly, the activation of peroxisome proliferator-activated receptor (PPAR), which belongs to the nuclear receptor superfamily, has many beneficial clinical effects. PPAR directly modulates gene expression by binding to a specific ligand. All PPAR subtypes (alpha, gamma, and sigma) are involved in glucose metabolism, lipid metabolism, and energy balance. PPAR agonists play an important role in therapeutic aspects of metabolic disorders. However, undesired effects of the existing PPAR agonists have been reported. A great deal of recent research has focused on the discovery of new PPAR modulators with more beneficial effects and more safety without producing undesired side effects. Herein, we briefly review the roles of PPAR in metabolic disorders, the effects of PPAR modulators in metabolic disorders, and the technologies with which to discover new PPAR modulators.

Fibrates, glitazones, and peroxisome proliferator-activated receptors

Several decades ago, fibrates were approved for the treatment of dyslipidemia, whereas thiazolidinediones were screened in animal models to improve glucose homeostasis and were subsequently developed for the treatment of type 2 diabetes mellitus. Relatively recently, these drugs were found to act via peroxisome proliferator-activated receptors, nuclear receptors that control lipid metabolism and glucose homeostasis. In this historical perspective, we discuss the history of discovery of the peroxisome proliferator-activated receptors, from the clinical development of their agonists to the subsequent discovery of these receptors and their mechanisms of action, to finally evoke possibilities of targeted pharmacology for future development of selective peroxisome proliferator-activated receptor modulators.

Lipids as targets for novel anti-inflammatory therapies

Lipids serve important functions as membrane constituents and also as energy storing molecules. Besides these functions certain lipid species have now been recognized as signalling molecules that regulate a multitude of cellular responses including cell growth and death, and also inflammatory reactions. Bioactive lipids are generated by hydrolysis from membrane lipids mainly by phospholipases giving rise to fatty acids and lysophospholipids that either directly exert their function or are further converted to active mediators. This review will summarize the present knowledge about bioactive lipids that either promote or attenuate inflammatory reactions. These lipids include polyunsaturated fatty acids (PUFA), eicosanoids including the epoxyeicosatrienoic acids (EET), peroxisome proliferation activating receptor (PPAR) activators, cannabinoids and the sphingolipids ceramide, sphingosine 1-phosphate and sphingosylphosphorylcholine.

Antihyperglycemic effect of a new thiazolidinedione analogue and its role in ameliorating oxidative stress in alloxan-induced diabetic rats

Thiazolidinediones (TZDs) are a new class of antidiabetic drugs, having an insulin sensitizing effect in patients with type 2 diabetes. The contribution of oxidative stress from the standpoint of lipid and protein damage, alteration in endogenous antioxidant enzymes and effects of newly synthesized compounds, 5-[4-2-(6,7-Dimethyl-1,2,3,4-tetrahydro-2-oxo-4-quinoxalinyl)ethoxy]phenyl]methylene]thiazolid- ine-2,4-dione, (C(1)) in normal/alloxan-induced diabetic rats form the focus area of this study. Its effect was compared to two well-known TZDs, namely pioglitazone and rosiglitazone. It has been concluded from results that after thirty days of administration of C(1), Pg and Rg in alloxan-induced diabetic animal groups, the blood glucose level decreased, more remarkably in C(1) treated group. Also oxidative damage has been studied by estimating hepatic superoxide dismutase (SOD) activity, which was found to be increased (p<0.001 vs. control). An inverse change in SOD values between hepatic and pancreatic/kidney tissues were observed. Treatment with the test compounds lowered the activity of SOD in liver while increased its activity in kidney and pancreas. Similar normalizing effect of C(1) on liver, pancreatic and renal catalase (CAT)/ glutathione peroxidase (GPx) activities were pronounced in diabetic rats (p<0.001 vs. diabetic rats). Decreased reduced glutathione (GSH) content, found in diabetic animals, was significantly elevated to normal levels by C(1) treatment. The treatment with C(1) also decreased the levels of nitric oxide and increased the activities of glutathione-s-transferase and glutathione reductase, as compared to diabetic animals. Evidence of oxidative damage to lipids and proteins was shown through the quantification of protein carbonyl (in tissues) and malondialdehyde levels (both serum and tissues). It was observed that the protein/lipid damage in diabetic rats was improved by treatment with C(1). Total antioxidant activity (TAA) was found to be enhanced in C(1) treated rats (p>0.05 vs. group3, p<0.001 vs. group2, p<0.001 vs. group 4). These results suggest that the newly synthesized TZD derivative (C(1)) has a potential to act as antihyperglycemic and antioxidant agent. In addition, for all parameters checked, it has better efficacy than rosiglitazone and is as effective as pioglitazone.

Nuclear receptor antagonists designed based on the helix-folding inhibition hypothesis

Here we review our studies on the molecular design of nuclear receptor antagonists, including retinoic acid receptor (RAR) antagonists, retinoid X receptor (RXR) antagonists, androgen receptor (AR) antagonists, and vitamin D receptor (VDR) antagonists, based on inhibition of folding of helix 12, which contains a co-activator binding site. Recent progress in structural development studies of peroxisome proliferator-activated receptor (PPAR) ligands is also reviewed.

Design, synthesis and evaluation of carbazole derivatives as PPAR alpha/gamma dual agonists and antioxidants

A series of hydroxycarbazole derivatives were synthesized and evaluated for PPAR alpha/gamma dual agonist as well as antioxidant activities. While most compounds showed good antioxidant activity, some compounds were identified as potential PPAR alpha/gamma dual agonists as well. Compounds 10a and 16 were found to be active in animal studies.

Adiponectin: a relevant player in PPARgamma-agonist-mediated improvements in hepatic insulin sensitivity?

The potent insulin-sensitizing effects of peroxisome proliferator-activated receptor gamma (PPARgamma) agonists are well established. However, it is still a matter of intense debate as to which tissue(s) represent the most critical sites of action for PPARgamma agonists, and what the relevant target genes are that ultimately mediate the improvements in insulin sensitivity. The cell type with the highest levels of PPARgamma is the adipocyte, and as such the adipocyte is an excellent candidate cell to look for critical mediators of PPARgamma agonist action. Adiponectin, an adipocyte-specific secretory protein, is upregulated in response to PPARgamma agonist exposure, and its serum levels consequently increase significantly. Genetic, pharmacological and clinical studies have demonstrated potent insulin-sensitizing effects of adiponectin. Here, we summarize the evidence that implicates adiponectin as a critical mediator of PPARgamma-agonist-mediated improvements in insulin sensitivity, particularly in the context of PPARgamma-agonist-mediated enhancements of hepatic insulin sensitivity.

5-aryl thiazolidine-2,4-diones: discovery of PPAR dual alpha/gamma agonists as antidiabetic agents

A novel series of 5-aryl thiazolidine-2,4-diones based dual PPARalpha/gamma agonists was identified. A number of highly potent and orally bioavailable analogues were synthesized. Efficacy study results of some of these analogues in the db/db mice model of type 2 diabetes showed them superior to rosiglitazone in correcting hyperglycemia and hypertriglyceridemia.

5-Aryl thiazolidine-2,4-diones as selective PPARgamma agonists

A series of 5-aryl thiazolidine-2,4-diones containing 4-phenoxyphenyl side chains was designed, synthesized, and evaluated for PPAR agonist activities. One such compound 28 exhibited comparable levels of glucose correction to rosiglitazone in the db/db mouse type 2 diabetes animal model.

Phenylacetic acid derivatives as hPPAR agonists

Beginning with the weakly active lead structure 1, a new series of hPPAR agonists was developed. In vivo glucose and triglyceride lowering activity was obtained by homologation and oxamination to 3, then conversion to substituted benzisoxazoles 4 and 5. Further manipulation afforded benzofurans 6 and 7. Compound 7 was of comparable potency as a glucose and triglyceride lowering agent in insulin resistant rodents to BRL 49653.

[Discovery and development of a new insulin sensitizing agent, pioglitazone]

Insulin resistance is a characteristic feature of type II diabetes as well as obesity. This insulin resistant state at the peripheral tissue level causes impaired glucose utilization, leading to hyperglycemia. Studies of antidiabetic agents by Takeda originated more than three decades ago when KK mice were introduced, followed by the development of a highly insulin-resistant animal model, KKAy mice. The first 2,4-thiazolidinedione derivative AL-321, which exhibited hypoglycemic effects in KKAy mice, was discovered by modification of the hypolipidemic agent AL-294 as a lead compound. Extensive structure-activity relationship studies on the analogues of AL-321 led to the selection of ciglitazone (ADD-3878) as a candidate for clinical evaluation. Ciglitazone, a prototypical compound in the series, was shown to normalize hyperglycemia, hyperinsulinemia, and hypertriglyceridemia in various insulin-resistant animal models without altering normoglycemia in nondiabetic animal models. However, it appeared that a more potent compound was needed for further clinical evaluation of this class of compound. Further study of this series of compounds led to the finding of pioglitazone (AD-4833) as a promising clinical candidate. Pioglitazone clearly ameliorates the abnormal glucose and lipid metabolism in diabetic patients and was marketed in the USA in August 1999 for the treatment of type II diabetes. Pioglitazone is now marketed in more than 40 countries world wide. Historical aspects of our studies on pioglitazone and its biological activities are described.

[Insulin resistance-reducing effect of a new thiazolidinedione derivative, pioglitazone]

Takeda has a relatively long history in diabetes research. Pioglitazone, a thiazolidinedione derivative, was developed from our basic research on diabetic animal models in the 1960s and our chemical research on lipid-lowering agents in the 1970s. Pioglitazone reduced plasma glucose, triglyceride and insulin levels in obese-diabetic animal models with insulin resistance in liver and/or peripheral tissues, but did not decrease normoglycemia in normal rats and aged dogs or hyperglycemia in insulin-deficient streptozocin-induced diabetic rats and impaired-insulin-secretory Goto-Kakizaki rats. The ED50 of plasma glucose-lowering action was 0.5 mg/kg/day in Wistar fatty rats. These findings clearly indicate that pioglitazone works in animals with insulin resistance and has a quite different mechanism from sulfonylureas and insulin itself. Although the exact mechanism of pioglitazone still remains obscure, pioglitazone normalized abnormalities in the cellular signal transduction of insulin. These effects seem to be due to the inhibitory action of pioglitazone on TNF-alpha production, which is one of the factors responsible for insulin resistance. Pioglitazone is a potent agonist for the peroxisome proliferator-activated receptor, (PPAR)-gamma, that is related to differentiation of adipocytes, and the relationship between TNF-alpha production and PPAR-gamma has been reported. Therefore, the agonistic activity of pioglitazone on PPAR-gamma may be involved in the mechanism of reduction of insulin resistance. The clinical data clearly demonstrated that pioglitazone, at clinical doses of 15-45 mg/day, decreased plasma glucose, HbA1c and triglyceride, increased plasma HDL-cholesterol, but did not alter total cholesterol and LDL-cholesterol levels. These findings suggest that pioglitazone has a benefit for prevention of cardiovascular diseases in addition to diabetic complications.

Three-dimensional quantitative structure activity relationships (3-D-QSAR) of antihyperglycemic agents

A three-dimensional quantitative structure activity relationship study (3-D-QSAR) was performed on a set of thiazolidinedione antihyperglycemic agents using the comparative molecular field analysis (CoMFA) method. The CoMFA models were derived from a training set of 53 compounds. Fifteen compounds, which were not used in model generation were used to validate the CoMFA models. All the compounds were superimposed to the template structure by atom-based and shape-based strategies. The SYBYL QSAR rigid body field fit was also used for aligning the ligands. A total of twelve different alignments were generated. The resulting models exhibited a good cross-validated r2cv values (0.624-0.764) and the conventional r2 values (0.689-0.921). A more robust cross-validation test using cross-validation by 2 groups (leave half out method) was performed 100 times to ascertain the predictiveness of the CoMFA models. The mean of r2cv values from 100 runs ranged from 0.611-0.690. Few models exhibited good external predictivity. These models were then used to define a hypothetical receptor model for antihyperglycemic agents.

Recent developments in oral hypoglycemic agents

Recent large-scale studies in patients with type 2 diabetes have suggested that improved glycemic control will reduce the incidence and severity of chronic complications. However, it is difficult to maintain the blood glucose levels of diabetic patients within a narrow range. Since insulin resistance and impaired insulin secretion cause hyperglycemia in type 2 diabetes, both improvement of insulin resistance and compensation for defective insulin secretion are necessary. Recently, the first insulin sensitizer was released, and a short-acting insulinotropic agent, which should be more convenient for strict glycemic control than sulfonylureas, has also been launched. This review focuses on these two new classes of hypoglycemic agents.

(3-substituted benzyl)thiazolidine-2,4-diones as structurally new antihyperglycemic agents

A series of 3-[(2,4-dioxothiazolidin-5-yl)methyl]benzamide derivatives was prepared as part of a search for antidiabetic agents. A structure-activity relationship study of these compounds led to the identification of 5-[(2,4-dioxothiazolidin-5-yl)methyl]-2-methoxy-N-[[4-(trifluorome thyl)-phenyl]methyl]benzamide (KRP-297) as a candidate drug for the treatment of diabetes mellitus.

Novel euglycemic and hypolipidemic agents: Part-2. Antioxidant moiety as structural motif

Several thiazolidinediones having antioxidant moities in their structural motif have been synthesised and evaluated for their euglycemic and hypolipidemic activities. A few of them have been found to be superior to troglitazone.