Nam Sook Kang

Anti-diabetic and anti-adipogenic effects of a novel selective 11β-hydroxysteroid dehydrogenase type 1 inhibitor, 2-(3-benzoyl)-4-hydroxy-1,1-dioxo-2H-1,2-benzothiazine-2-yl-1-phenylethanone (KR-66344)

The selective inhibitors of 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) have considerable potential for treating type 2 diabetes mellitus and metabolic syndrome. In the present study, we investigated the anti-diabetic and anti-adipogenic effects of 2-(3-benzoyl)-4-hydroxy-1,1-dioxo-2H-1,2-benzothiazine-2-yl-1-phenylethanone (KR-66344), as a 11β-HSD1 inhibitor; we also investigated the underlying molecular mechanisms in the cortisone-induced 3T3-L1 adipogenesis model system and C57BL/6-Lep(ob/ob) mice. KR-66344 concentration-dependently inhibited 11β-HSD1 activity in human liver microsome, mouse C2C12 myotube and human SW982 cells. In the C57BL/6-Lep(ob/ob) mice study, the administration of KR-66344 (200mg/kg/d, orally for 5 days) improved the glucose intolerance as determined by the oral glucose tolerance test, in which the area under the curve (AUC) of the plasma glucose concentration was significantly reduced by 27% compared with the vehicle treated group. Further, KR-66344 suppressed adipocyte differentiation on cortisone-induced adipogenesis in 3T3-L1 cells is associated with the suppression of the cortisone-induced mRNA levels of FABP4, G3PD, PPARγ2 and Glut4, and 11β-HSD1 expression and activity. Our results additionally demonstrate evidence showing that KR-66344 improved glycemic control and inhibited adipogenesis via 11β-HSD1 enzyme activity. Taken together, these results may provide evidence of the therapeutic potential of KR-66344, as a 11β-HSD1 inhibitor, in obesity and type 2 diabetes patients with metabolic syndrome.

Augmentation of PPARγ-TAZ interaction contributes to the anti-adipogenic activity of KR62980

Peroxisome proliferator-activated receptor gamma (PPARgamma) is a ligand-activated transcription factor that plays a pivotal role in the modulation of gene expression involved in adipocyte differentiation and insulin sensitivity. It has been previously established that thiazolidinedione (TZD) PPARgamma ligands such as rosiglitazone have potent anti-diabetic and adipogenic activities. A novel non-TZD ligand for PPARgamma, KR62980 has recently been characterized to increase insulin sensitivity and to be weakly adipogenic in 3T3-L1 cells or anti-adipogenic in rosiglitazone-induced adipocyte differentiation. In this study, we have confirmed that KR62980 substantially suppresses rosiglitazone-induced adipocyte differentiation and attenuates adipogenic gene expression via an induced reduction in PPARgamma activity. KR62980 increased the nuclear localization of TAZ, a PPARgamma suppressor, and also enhanced the interaction between PPARgamma and TAZ, thus resulting in the TAZ-mediated suppression of PPARgamma activity. Furthermore, KR62980 failed to suppress PPARgamma-mediated adipogenic gene expression and adipocyte differentiation in TAZ knockdown 3T3-L1 cells, thus indicating a TAZ-dependent suppressive activity of KR62980 on PPARgamma-mediated function. These findings strongly suggest that the novel PPARgamma ligand, KR62980, may prove to be beneficial to anti-adipogenic function through the suppression of PPARgamma-mediated adipocyte differentiation by activating TAZ.

Reactivation potency of fluorinated pyridinium oximes for acetylcholinesterases inhibited by paraoxon organophosphorus agent

For the purpose of developing new oxime reactivators of acetylcholinesterases (AChE) that have been inhibited by organophosphorus agents, emphasis was given to the finding that the lipophilic nature of fluorinated compounds is responsible for their enhanced transport across the blood brain barrier (BBB). As a result, we have designed and synthesized the fluorinated oxime derivatives, which quantum mechanical calculations suggest should have a greater lipophilicity and BBB permeability than their non-fluorinated analogs. Among the compounds explored in this study, 4 was found to have the highest potency for reactivation of paraoxon-inhibited housefly (HF) AChE.

Cardiovascular effects of a novel selective Rho kinase inhibitor, 2-(1H-indazole-5-yl)amino-4-methoxy-6-piperazino triazine (DW1865)

The arising critical implications of Rho kinase signaling in cardiovascular diseases have been attracting attention in the pharmacological potential of Rho kinase inhibitors. We identified a novel inhibitor of Rho kinase (2-(1H-indazole-5-yl)amino-4-methoxy-6-piperazino triazine; DW 1865) and characterized its effects in biochemical, cellular, tissue and animal based assays. DW 1865 potently inhibited the kinase activity of both Rho kinase 1 and Rho kinase 2 in vitro, and behaved as an ATP-competitive inhibitor. Interestingly, DW1865 was 10 times more potent in inhibiting Rho kinase activities than fasudil as a selective Rho kinase inhibitor. The activity of DW1865 was shown to be highly selective for Rho kinase in the panel assay of 13 other kinases. In the isolated vascular tissue study, DW1865 exerted vasorelaxation in phenylephrine- or 5-hydroxytriptamine-induced contraction in a concentration-dependent manner manner. In spontaneously hypertensive rats, administration of DW1865 caused a significant and dose-related reduction in blood pressure. Furthermore, DW1865 blocked angiotensin II-induced stress fiber formation and cellular hypertrophy in rat heart-derived H9c2 cells. Taken together, these results suggest that DW1865 is a highly selective and potent Rho kinase inhibitor that will alleviate the pathophysiological actions of Rho kinase such as stress fiber formation, cellular hypertrophy, and hypertension.

Discovery of aminopyridines substituted with benzoxazole as orally active c-Met kinase inhibitors.

We report the synthesis and biological evaluation of aminopyridines substituted with benzoxazole. The SAR of the aminopyridines was explored to improve the inhibitory activity against c-Met and to decrease hERG affinity. These studies led to the discovery of amide 24 which showed good c-Met inhibitory potency, low affinity to hERG and favorable pharmacokinetic properties in rats.

Synthesis and biological evaluation of homopiperazine derivatives with beta-aminoacyl group as dipeptidyl peptidase IV inhibitors

Compounds with homopiperazine skeleton are designed to find a potent DPP-IV inhibitor without inhibiting CYP. Thus a series of beta-aminoacyl-containing homopiperazine derivatives was synthesized and evaluated. Compounds with acid moiety were found to be potent inhibitors of DPP-IV without inhibiting CYP 3A4. More specifically, compound 7m showed nanomolar activity with no inhibition towards five subtypes of CYPs, was considered as a prototype for further derivatization. Based on its X-ray co-crystal structure with human DPP-IV, we identified compounds 7s and 7t which showed good in vitro activity, no CYP inhibition, and good selectivity.

Synthesis and biological evaluation of pyrazoline analogues with β-amino acyl group as dipeptidyl peptidase IV inhibitors

A series of pyrazoline derivatives with beta-amino acyl group were synthesized and evaluated for their ability to inhibit dipeptidyl peptidase IV. Several pyrazoline derivatives exhibited submicromolar inhibitory activities against DPP-IV. X-ray co-crystal structure of initial hit compound 1h was determined. Among this series, carboxylic acid substituted pyrazoline derivative 2u was the most active and greatly decreased the inhibitory activity toward CYP3A4 enzyme.

KRC-408, a novel c-Met inhibitor, suppresses cell proliferation and angiogenesis of gastric cancer

Among many cancer therapeutic targets, c-Met receptor tyrosine kinase has recently given particular attention. This kinase and its ligand, hepatocyte growth factor (HGF), play a central role in cell proliferation and the survival of several human cancers. Thus, we developed KRC-408 as a novel c-Met inhibitor and investigated its anti-cancer effects on human gastric cancer. KRC-408 inhibited the phosphorylation of c-Met and its constitutive downstream effectors such as phosphatidylinositol 3-kinase (PI3K), Akt, Mek, and Erk. This compound was found to exert anti-cancer effects stronger than those of 5-fluorouracil (5-FU) on gastric cancer cells, especially cell lines that overexpressed c-Met. Interestingly, cytotoxicity of KRC-408 was lower than that of 5-FU in normal gastric cells. Apoptosis induced by KRC-408 was accompanied by increased levels of cleaved caspase-3 and PARP as well as DNA condensation and fragmentation. Flow cytometry analysis showed an accumulation of gastric cancer cells in the G2/M phase with concomitant loss of cells in the S phase following treatment with this drug. In the angiogenesis studies, KRC-408 inhibited tube formation and migration of human umbilical vein endothelial cells (HUVECs), and suppressed microvessel sprouting from rat aortic rings ex vivo along with blood vessel formation in a Matrigel plug assay in mice. Results of an in vivo mouse xenograft experiment showed that the administration of KRC-408 significantly delayed tumor growth in a dose-dependent manner, and suppressed Akt and Erk phosphorylation as well CD34 expression in tumor tissues. These findings indicate that KCR-408 may exert anti-tumor effects by directly affecting tumor cell growth or survival via the c-Met receptor tyrosine kinase pathway. We therefore suggest that KRC-408 is a novel therapeutic candidate effective against gastric cancers that overexpress c-Met.

Discovery of a potent small molecule SIRT1/2 inhibitor with anticancer effects

SIRT1 and SIRT2 are deacetylase enzymes that belong to the sirtuin family and are involved in tumorigenesis. In our screen for small molecules inhibiting SIRT1/2 toxoflavin was identified. Toxoflavin potently inhibited SIRT1 activity in in vitro deacetylase assay using purified SIRT1 protein. SIRT2 activity was also inhibited by toxoflavin less potently than SIRT1 in deacetylase assay in vitro. Toxoflavin exhibited growth inhibition of various cancer cell lines including A549 lung cancer cells with a GI(50) of 48 nM. Toxoflavin treatment in A549 cells increased the acetylated form of p53, which is a substrate of SIRT1. The acetylation levels of α-tubulin, a SIRT2 substrate, were also increased by toxoflavin treatment dose-dependently. Several toxoflavin derivatives were synthesized to determine the preliminary structure-activity relationship of toxoflavin. Some of the toxoflavin derivatives showed highly selective inhibition against SIRT1. In conclusion, this study presented toxoflavin as a potent SIRT1/2 inhibitor with anticancer activity.

Classification models for CYP450 3A4 inhibitors and non-inhibitors.

Cytochrome P450 3A4 (CYP3A4) is the predominant enzyme involved in the oxidative metabolic pathways of many drugs. The inhibition of this enzyme in many cases leads to an undesired accumulation of the administered therapeutic agent. The purpose of this study is to develop in silico model that can effectively distinguish human CYP3A4 inhibitors from non-inhibitors. Structural diversity of the drug-like compounds CYP3A4 inhibitors and non-inhibitors was obtained from Fujitsu Database and Korea Research Institute of Chemical Technology (KRICT) as training and test sets, respectively. Recursive Partitioning (RP) method was introduced for the classification of inhibitor and non-inhibitor of CYP3A4 because it is an easy and quick classification method to implement. The 2D molecular descriptors were used to classify the compounds into respective inhibitors and non-inhibitors by calculation of the physicochemical properties of CYP3A4 inhibitors such as molecular weights and fractions of 2D VSA chargeable groups. The RP tree model reached 72.33% of accuracy and exceeded this percentage for the sensitivity (75.82%) parameter. This model is further validated by the test set where both accuracy and sensitivity were 72.58% and 82.64%, respectively. The accuracy of the random forest model was increased to 73.8%. The 2D descriptors sufficiently represented the molecular features of CYP3A4 inhibitors. Our model can be used for the prediction of either CYP3A4 inhibitors or non-inhibitors in the early stages of the drug discovery process.