Nonpeptide small-molecular inhibitors of dipeptidyl peptidase IV: N-phenylphthalimide analogs

Novel Potent and Selective DPP-4 Inhibitors: Design, Synthesis and Molecular Docking Study of Dihydropyrimidine Phthalimide Hybrids

Background: Dipeptidyl peptidase-4 (DPP-4) inhibitors have emerged as anti-hyperglycemic agents that improve glycemic control in type 2 diabetic patients, either as monotherapy or in combination with other antidiabetic drugs. Methods: A novel series of dihydropyrimidine phthalimide hybrids was synthesized and evaluated for their in vitro and in vivo DPP-4 inhibition activity and selectivity using alogliptin as reference. Oral glucose tolerance test was assessed in type 2 diabetic rats after chronic treatment with the synthesized hybrids ± metformin. Cytotoxicity and antioxidant assays were performed. Additionally, molecular docking study with DPP-4 and structure activity relationship of the novel hybrids were also studied. Results: Among the synthesized hybrids, 10g, 10i, 10e, 10d and 10b had stronger in vitro DPP-4 inhibitory activity than alogliptin. Moreover, an in vivo DPP-4 inhibition assay revealed that 10g and 10i have the strongest and the most extended blood DPP-4 inhibitory activity compared to alogliptin. In type 2 diabetic rats, hybrids 10g, 10i and 10e exhibited better glycemic control than alogliptin, an effect that further supported by metformin combination. Finally, 10j, 10e, 10h and 10d had the highest radical scavenging activity in DPPH assay. Conclusions: Hybrids 10g, 10i and 10e are potent DPP-4 inhibitors which may be beneficial for T2DM treatment.

Synthesis of N-phenylphthalimide derivatives as alpha-glucosidase inhibitors

Sixteen N-phenylphthalimide derivatives were synthesized and their ability to inhibit alpha-glucosidase was investigated. N-(2,4-dinitrophenyl)phthalimide was a potent inhibitor of yeast alpha-glucosidase (IC50; 0.158 +/- 0.005 mM) and maltase (IC50; 0.051 +/- 0.008 mM), whereas it did not inhibit sucrase. From a Lineweaver-Burk plot of alpha-glucosidase kinetics, N-(2,4-dichlorophenyl)phthalimide was found to be a competitive inhibitor of yeast alpha-glucosidase. These results indicate that N-(2,4-dinitrophenyl)phthalimide could be a representative of a new group of alpha-glucosidase inhibitors.

Liver X receptor antagonists with a phthalimide skeleton derived from thalidomide-related glucosidase inhibitors

Alpha-glucosidase inhibitors with a chlorinated phthalimide or a thiophthalimide skeleton, derived from thalidomide, were found to possess liver X receptor (LXR) antagonistic activity. Novel LXR antagonists with a 2'-substituted phenylphthalimide skeleton were obtained by structural development of glucosidase inhibitors derived from thalidomide.

Structural development studies of nuclear receptor ligands

Studies in our laboratory are focused on structural development studies of biological response modifiers (BRMs), including nuclear receptor (NR) ligands, which act directly on cells at the gene expression level, and thalidomide (and related molecules), which modulates a variety of physiological processes. Our studies on the molecular design of ligands for retinoic acid receptor (RAR), androgen receptor (AR), vitamin D receptor (VDR), farnesoid X receptor (FXR), and peroxisome proliferator-activated receptor (PPAR) are reviewed.

Aminopeptidase-N/CD13 (EC 3.4.11.2) inhibitors: chemistry, biological evaluations, and therapeutic prospects

Aminopeptidase N (APN)/CD13 (EC 3.4.11.2) is a transmembrane protease present in a wide variety of human tissues and cell types (endothelial, epithelial, fibroblast, leukocyte). APN/CD13 expression is dysregulated in inflammatory diseases and in cancers (solid and hematologic tumors). APN/CD13 serves as a receptor for coronaviruses. Natural and synthetic inhibitors of APN activity have been characterized. These inhibitors have revealed that APN is able to modulate bioactive peptide responses (pain management, vasopressin release) and to influence immune functions and major biological events (cell proliferation, secretion, invasion, angiogenesis). Therefore, inhibition of APN/CD13 may lead to the development of anti-cancer and anti-inflammatory drugs. This review provides an update on the biological and pharmacological profiles of known natural and synthetic APN inhibitors. Current status on their potential use as therapeutic agents is discussed with regard to toxicity and specificity.

Design and synthesis of phthalimide-type histone deacetylase inhibitors

Several hydroxamic acid derivatives with a substituted phthalimide group as a linker and/or cap structure, prepared during structural development studies based on thalidomide, were found to have histone deacetylase (HDAC)-inhibitory activity. Structure-activity relationship studies indicated that nature of the substituent introduced at the phthalimide nitrogen atom, introduction of a hydroxamic acid structure, and distance between the N-hydroxyl group and the cap structure are important for HDAC-inhibitory activity.

Design and synthesis of subtype-selective cyclooxygenase (COX) inhibitors derived from thalidomide

A series of substituted indoline and indole derivatives with cyclooxygenase (COX)-inhibitory activity was prepared during our structural development studies based on thalidomide as a multi-template lead compound. Structure-activity relationship studies indicated that the nature of the substituent introduced at the benzene ring of the indoline (indole) backbone, and the length and type of the linking group between the nitrogen atom of indoline (indole) and the N-substituent are important for the activity. This study has led to the identification of COX-1-selective inhibitors, and these should be useful not only as pharmacological tools to investigate the physiology and pathophysiology of COX, but also as sophisticated leads for the development of novel drugs to treat COX-associated diseases, such as inflammatory diseases, and cancer.

Structure and function studies of glucagon-like peptide-1 (GLP-1): the designing of a novel pharmacological agent for the treatment of diabetes

Glucagon-like peptide-1 (GLP-1) is a proglucagon-derived peptide secreted from gut endocrine cells in response to nutrient ingestion. The multifaceted actions of GLP-1 include the following: (1) the stimulation of insulin secretion and of its gene expression, (2) the inhibition of glucagon secretion, (3) the inhibition of food intake, (4) the proliferation and differentiation of beta cells, and (5) the protection of beta-cells from apoptosis. The therapeutic utility of the native GLP-1 molecule is limited by its rapid enzymatic degradation by a serine protease termed dipeptidyl peptidase-IV (DPP-IV). The present article reviews the research studies aimed at elucidating the biosynthesis, metabolism, and molecular characteristics of GLP-1 since it is from these studies that the development of a GLP-1-like pharmacological agent may be derived.

Thalidomide as a Nitric Oxide Synthase Inhibitor and Its Structural Development

Thalidomide has been found to exhibit weak nitric oxide synthase (NOS)-inhibitory activity. Structural development studies of thalidomide showed that some N-2,6-dimethylphenylhomophthalimide analogs possess NOS-inhibiting activity.

N-Phenylphthalimide-Type Cyclooxygenase (COX) Inhibitors Derived from Thalidomide: Substituent Effects on Subtype Selectivity

Several N-substituted phenylphthalimide and phenylhomophthalimide derivatives with cyclooxygenase (COX)-inhibitory activity were prepared during structural development studies based on thalidomide as a lead compound. Substituent effects on the subtype selectivity were investigated.

Cyclooxygenase inhibitors derived from thalidomide

Several N-3,5-dimethylphenylphthalimide analogs possessing more potent cyclooxygenase-inhibiting activity than that of aspirin were prepared during structural development studies based on thalidomide. Substituent effects on the activity were investigated.

Dipeptidyl-peptidase IV from bench to bedside: an update on structural properties, functions, and clinical aspects of the enzyme DPP IV

Dipeptidyl-peptidase IV/CD26 (DPP IV) is a cell-surface protease belonging to the prolyloligopeptidase family. It selectively removes the N-terminal dipeptide from peptides with proline or alanine in the second position. Apart from its catalytic activity, it interacts with several proteins, for instance, adenosine deaminase, the HIV gp120 protein, fibronectin, collagen, the chemokine receptor CXCR4, and the tyrosine phosphatase CD45. DPP IV is expressed on a specific set of T lymphocytes, where it is up-regulated after activation. It is also expressed in a variety of tissues, primarily on endothelial and epithelial cells. A soluble form is present in plasma and other body fluids. DPP IV has been proposed as a diagnostic or prognostic marker for various tumors, hematological malignancies, immunological, inflammatory, psychoneuroendocrine disorders, and viral infections. DPP IV truncates many bioactive peptides of medical importance. It plays a role in glucose homeostasis through proteolytic inactivation of the incretins. DPP IV inhibitors improve glucose tolerance and pancreatic islet cell function in animal models of type 2 diabetes and in diabetic patients. The role of DPP IV/ CD26 within the immune system is a combination of its exopeptidase activity and its interactions with different molecules. This enables DPP IV/CD26 to serve as a co-stimulatory molecule to influence T cell activity and to modulate chemotaxis. DPP IV is also implicated in HIV-1 entry, malignant transformation, and tumor invasion.

Thalidomide and its analogues as cyclooxygenase inhibitors

Thalidomide showed cyclooxygenase (COX)-1/2 inhibitory activity with a potency comparable to that of aspirin. Structural development studies of thalidomide resulted in potent COX-1/2 inhibitors, and COX-1-selective and COX-2-selective inhibitors.

Structural development of biological response modifiers based on thalidomide

Thalidomide (N-alpha-phthalimidoglutarimide) is a teratogenic hypnotic/sedative agent which was used widely in the late 1950s and the early 1960s. In spite of its withdrawal from the market because of its severe teratogenicity, there has been a resurgence of interest in the drug in recent years due to its potential usefulness for the treatment of various diseases, including acquired immunodeficiency syndrome (AIDS) and various cancers. It has been revealed that thalidomide elicits pleiotropic effects and is a multi-target drug. Our structural development studies of thalidomide, focusing on tumor necrosis factor-alpha(TNF-alpha) production-regulating activity, anti-androgenic activity, puromycin-sensitive aminopeptidase-inhibiting activity, alpha-glucosidase-inhibiting activity, and inhibitory activities toward some other enzymes, are reviewed in relation to the pharmacological effects of thalidomide.

Thymidine phosphorylase inhibitors with a homophthalimide skeleton

Several N-phenylhomophthalimide derivatives were prepared and their inhibitory activity on thymidine phosphorylase/ platelet-derived endothelial cell growth factor (TP/PD-ECGF) was assessed. Among them, 2-(2,6-diethylphenyl)-7-nitro-1,2,3,4-tetrahydroisoquinoline-1,3-dione (9) was found to be a more potent inhibitor than the classical inhibitor, 5-nitrouracil (1). Lineweaver-Burk plot analysis indicated that 9 shows mixed-type competitive inhibition of TP/PD-ECGF, while 1 is a competitive inhibitor.

Specific inhibitor of puromycin-sensitive aminopeptidase with a homophthalimide skeleton: identification of the target molecule and a structure-activity relationship study

2-(2,6-Diethylphenyl)-1,2,3,4-tetrahydroisoquinoline-1,3-dione (2: PIQ-22) was found to be a potent and specific inhibitor of puromycin-sensitive aminopeptidase (PSA). Lineweaver-Burk plot analysis showed that PSA is inhibited by PIQ-22 in a non-competitive manner. Structure -activity relationship studies indicated that tautomerism of the imidobenzoylketone group in the cyclic imide moiety of the PIQ-22 skeleton is important for the inhibitory activity.