A novel series of 4-phenoxyquinolines: potent and highly selective inhibitors of PDGF receptor autophosphorylation

Umpolung Synthesis of Pyridyl Ethers by BiV -Mediated O-Arylation of Pyridones

We report that O-selective arylation of 2- and 4-pyridones with arylboronic acids is affected by a modular, bismacycle-based system. The utility of this umpolung approach to pyridyl ethers, which is complementary to conventional methods based on S_N Ar or cross-coupling, is demonstrated through the concise synthesis of Ki6783 and picolinafen, and the formal synthesis of cabozantib and golvatinib. Computational investigations reveal that arylation proceeds in a concerted fashion via a 5-membered transition state. The kinetically-controlled regioselectivity for O-arylation-which is reversed relative to previous Bi^V -mediated pyridone arylations-is attributed primarily to the geometric constraints imposed by the bismacyclic scaffold.

Assays for membrane tyrosine kinase receptors: methods for high-throughput screening and utility for diagnostics

The development of novel antagonists or agonists of membrane tyrosine kinase receptors is a large focus of discovery research. This review will provide some background on membrane tyrosine kinases as well as a description of some of the better established assays used for the high-throughput screening of membrane tyrosine kinase inhibitors. Biochemical methods detailed include those using labels such as radioactivity and fluorescence (fluorescence energy transfer, fluorescence and fluorescence polarization) as well as label-free assays using luminescence. These assays are solid phase, liquid phase, as well as bead based. In addition, a discussion on which tools are available to screen for membrane tyrosine kinase receptor modulators/activators using whole-cell assays will be presented. The potential clinical need for testing receptor activation/phosphorylation as well as the possibility of using some of these tests to measure biomarkers of disease or as clinical diagnostic tools to tailor drug therapy or monitor its efficacy will also be discussed.

Design, synthesis, and DNA-binding of N-alkyl(anilino)quinazoline derivatives

New N-alkylanilinoquinazoline derivatives 5, 12, 20, and 22 have been prepared from 4-chloro-6,7-dimethoxyquinazoline 3, 4-chloro-6,7-methylenedioxyquinazoline 19, and commercially available anilines. Differents classes of compounds substituted by an aryloxygroup (6a-c, 16a,b, and 17a,b), (aminophenyl)ureas (12a,b and 13a-f), anilines (4a-m, 20a,b), N-alkyl(aniline) (5a-m, 21a,b, 22a,d), and N-aminoalkyl(aniline) (22e-g) have been synthesized. These molecules were evaluated for their cytotoxic activities and as potential DNA intercalating agents. We studied the strength and mode of binding to DNA of these molecules by DNA melting temperature measurements, fluorescence emission, and circular dichroism. The results of various spectral and gel electrophoresis techniques obtained with the different compounds, in particular compounds 5g and 22f, revealed significant DNA interaction. These experiments confirm that the N-aminoalkyl(anilino)-6,7-dimethoxyquinazoline nucleus is an efficient pharmacophore to trigger binding to DNA, via an intercalative binding process.

Development of linear, ensemble, and nonlinear models for the prediction and interpretation of the biological activity of a set of PDGFR inhibitors

A QSAR modeling study has been done with a set of 79 piperazyinylquinazoline analogues which exhibit PDGFR inhibition. Linear regression and nonlinear computational neural network models were developed. The regression model was developed with a focus on interpretative ability using a PLS technique. However, it also exhibits a good predictive ability after outlier removal. The nonlinear CNN model had superior predictive ability compared to the linear model with a training set error of 0.22 log(IC50) units (R2 = 0.93) and a prediction set error of 0.32 log(IC50) units (R2 = 0.61). A random forest model was also developed to provide an alternate measure of descriptor importance. This approach ranks descriptors, and its results confirm the importance of specific descriptors as characterized by the PLS technique. In addition the neural network model contains the two most important descriptors indicated by the random forest model.

Orally active anti-proliferation agents: novel diphenylamine derivatives as FGF-R2 autophosphorylation inhibitors

(6,7-Disubstituted-quinolin-4-yloxy-phenyl)(4-substituted-phenyl)amine derivatives were synthesized and evaluated by a cellular autophosphorylation assay for FGF-R2 in the human scirrhous gastric carcinoma cell line, OCUM-2MD3. We also performed metabolic stability studies showing that substitutions at the 7-position of quinoline affect its biological stability. In this study, we achieved a remarkable improvement in the solubility and metabolic stability of the diphenylamine derivative. The most promising compound 15e showed a significant decrease in tumor volume when orally administered.

Synthesis and structure–activity relationship for new series of 4-Phenoxyquinoline derivatives as specific inhibitors of platelet-derived growth factor receptor tyrosine kinase

We discovered a new series of 4-phenoxyquinoline derivatives as potent and selective inhibitors of the platelet-derived growth factor receptor (PDGFr) tyrosine kinase. We researched the highly potent and selective inhibitors on the basis of both PDGFr and epidermal growth factor receptor (EGFr) inhibitory activity. First, we found a compound, Ki6783 (1), which inhibited PDGFr autophosphorylation at 0.13 microM, but it did not inhibit EGFr autophosphorylation at 100 microM. After extensive explorations, we found the two desired compounds, Ki6896 (2) and Ki6945 (3), which are substituted by benzoyl and benzamide at the 4-position of the phenoxy group on 4-phenoxyquinoline, respectively. These inhibitory activities were 0.31 and 0.050 microM, respectively, but neither of them inhibited EGFr autophosphorylation at 100 microM. We further investigated the profile of both compounds toward various tyrosine and serine/threonine kinases. The three compounds specifically inhibited PDGFr rather than the other kinases.

Synthesis and structure-activity relationship of diarylamide derivatives as selective inhibitors of the proliferation of human endothelial cells

A series of diarylamide urea derivatives were synthesized and evaluated for their inhibitory activities against human coronary artery endothelial cells (ECs) and human coronary artery smooth muscle cells (SMCs). Compound was superior to Tranilast, in terms of both cell selectivity and the potency of its inhibitory activity toward the proliferation and angiogenesis of ECs.

Identification of orally active, potent, and selective 4-piperazinylquinazolines as antagonists of the platelet-derived growth factor receptor tyrosine kinase family

We have previously found that the 4-[4-(N-substituted carbamoyl)-1-piperazinyl]-6,7-dimethoxyquinazolines can function as potent and selective inhibitors of platelet-derived growth factor receptor (PDGFR) phosphorylation. A series of highly potent, specific, orally active, small molecule kinase inhibitors directed against members of PDGFR receptor have been developed through modifications of the novel quinazoline template I. Systematic modifications in the A-bicyclic ring and D-rings of protype I were carried out to afford potent analogues, which display IC(50) values of <250 nM in cellular betaPDGFR phosphorylation assays. An optimized analogue in this series, 75 (CT53518), inhibits Flt-3, betaPDGFR, and c-Kit receptor phosphorylation with IC(50) values of 50-200 nM, whereas 15-20-fold less potent activity against CSF-1R was observed. This analogue also inhibits autophosphorylation of Flt-3 ligand-stimulated wild-type Flt-3 and a constitutively activated Flt-3/internal tandem duplication (ITD) with IC(50) values of 30-100 nM. Through this optimization process, 75 was found to be metabolically stable and has desirable pharmacokinetic properties in all animal species studied (F% > 50%, T(1/2) > 8 h). Oral administration of 75 promotes mice survival and significantly delayed disease progression in a Flt-3/ITD-mediated leukemia mouse model and shows efficacy in a nude mouse model of chronic myelomonocytic leukemia.

Potent and selective inhibitors of platelet-derived growth factor receptor phosphorylation. 1. Synthesis, structure-activity relationship, and biological effects of a new class of quinazoline derivatives

A new series of 4-[4-(N-substituted carbamoyl)-1-piperazinyl]-6,7-dimethoxyquinazoline derivatives were found to show potent and selective inhibition of platelet-dervied growth factor (PDGF) receptor phosphorylation. In this exploration of the structure-activity relationships (SARs) of the prototype inhibitor KN1022, the 4-nitrophenylurea moiety was probed. We found that 4-substitution on the phenyl ring was optimal and the introduction of more than two substituents on the phenyl ring decreased activities. Bulky substituents on the phenyl ring enhanced activities. Thiourea analogues were also prepared, and the SARs were found to be slightly different from those of the urea derivatives. Through this research, we obtained some potent KN1022 derivatives such as 4-(4-methylphenoxy)phenyl (36, IC(50) 0.02 micromol/L), 4-tert-butylphenyl (16, IC(50) 0.03 micromol/L), and 4-phenoxyphenyl (21, IC(50) 0.08 micromol/L) analogues, which had almost a 10-fold increase in activity against KN1022. These potent compounds retained their high selectivity against the PDGF receptor family similar to KN1022. We also observed that these compounds could inhibit the PDGF-BB-induced proliferation of porcine vascular smooth muscle cells without cell toxicity almost at the same IC(50) values observed for PDGF receptor phosphorylation. To evaluate the biological effects in vivo, we selected some analogues on the basis of the measurement of the plasma drug concentration after oral administration to rats. Oral administration of the 4-chlorophenyl (6), 4-bromophenyl (9), or 4-isopropoxyphenyl (20) analogue to Sprague-Dawley rats (30 mg/kg, twice daily) resulted in significant inhibition (24-38%) of neointima formation in the carotid artery of the balloon catheter deendothelialized vessel in the rats. Therefore, 4-[4-(N-substituted carbamoyl)-1-piperazinyl]-6,7-dimethoxyquinazoline derivatives, which are potent inhibitors of PDGFR phosphorylation, may be expected to represent a new therapeutic approach for the treatment of various aspects of atherosclerosis and other cellular proliferative disorders.

Optimization of 4-phenylamino-3-quinolinecarbonitriles as potent inhibitors of Src kinase activity

Subsequent to the discovery of 4-[(2,4-dichlorophenyl)amino]-6,7-dimethoxy-3-quinolinecarbonitrile (1a) as an inhibitor of Src kinase activity (IC(50) = 30 nM), several additional analogues were prepared. Optimization of the C-4 anilino group of 1a led to 1c, which contains a 2,4-dichloro-5-methoxy-substituted aniline. Replacement of the methoxy group at C-7 of 1c with a 3-(morpholin-4-yl)propoxy group provided 2c, resulting in increased inhibition of both Src kinase activity and Src-mediated cell proliferation. Analogues of 2c with other trisubstituted anilines at C-4 were also potent Src inhibitors, and the propoxy group of 2c was preferred over ethoxy, butoxy, or pentoxy. Replacement of the morpholine group of 2c with a 4-methylpiperazine group provided 31a, which had an IC(50) of 1.2 nM in the Src enzymatic assay, an IC(50) of 100 nM for the inhibition of Src-dependent cell proliferation and was selective for Src over non-Src family kinases. Compound 31a, which had higher 1 and 4 h plasma levels than 2c, effectively inhibited tumor growth in xenograft models.

Synthesis and Src kinase inhibitory activity of a series of 4-phenylamino-3-quinolinecarbonitriles

Screening of a directed compound library in a yeast-based assay identified 4-[(2,4-dichlorophenyl)amino]-6,7-dimethoxy-3-quinolinecarbonitrile (2a) as a Src inhibitor. An enzymatic assay established that 2a was an ATP-competitive inhibitor of the kinase activity of Src. We present here SAR data for 2a which shows that the aniline group at C-4, the carbonitrile group at C-3, and the alkoxy groups at C-6 and C-7 of the quinoline are crucial for optimal activity. Increasing the size of the C-2 substituent of the aniline at C-4 of 2a from chloro to bromo to iodo resulted in a corresponding increase in Src inhibition. Furthermore, replacement of the 7-methoxy group of 2a with various 3-heteroalkylaminopropoxy groups provided increased inhibition of both Src enzymatic and cellular activity. Compound 25, which contains a 3-morpholinopropoxy group, had an IC(50) of 3.8 nM in the Src enzymatic assay and an IC(50) of 940 nM for the inhibition of Src-dependent cell proliferation.

Beneficial effects of a novel inhibitor of platelet-derived growth factor receptor autophosphorylation in the rat with mesangial proliferative glomerulonephritis

1. Our original compound, Ki6896 ((4-t-butylphenyl)(4-[(6,7-dimethoxy-4-quinolyl) oxy]phenyl) methanone) strongly inhibited the autophosphorylation of platelet-derived growth factor (PDGF) beta-receptor (IC50=0.31 microM) and that of basic fibroblast growth factor receptor (IC50=3.1 microM), whereas it did not inhibit some other kinases. 2. The [3H]thymidine incorporation and the growth of mesangial cells under the stimulation of PDGF were inhibited by Ki6896 in a dose-dependent manner. 3. In the mesangial proliferative glomerulonephritis rats induced by anti-Thy-1 monoclonal antibody, glomerulosclerosis was ameliorated and the number of glomerular proliferating cells was decreased by the daily administration of Ki6896. However, the accumulation of type I collagen and fibronectin in the glomeruli was not suppressed by Ki6896.

Synthesis and tyrosine kinase inhibitory activity of a series of 2-amino-8H-pyrido[2,3-d]pyrimidines: identification of potent, selective platelet-derived growth factor receptor tyrosine kinase inhibitors

Screening of a compound library led to the identification of 2-amino-6-(2,6-dichlorophenyl)-8-methylpyrido[2,3-d]pyrimidine (1) as a inhibitor of the platelet-derived growth factor receptor (PDGFr), fibroblast growth factor receptor (FGFr), and c-src tyrosine kinases (TKs). Replacement of the primary amino group at C-2 of 1 with a 4-(N,N-diethylaminoethoxy)phenylamino group yielded 2a, which had greatly increased activity against all three TKs. In the present work, variation of the aromatic group at C-6 and of the alkyl group at N-8 of the pyrido[2,3-d]pyrimidine core provided several analogues that retained potency, including derivatives that were biased toward inhibition of the TK activity of PDGFr. Analogues of 2a with a 3-thiophene or an unsubstituted phenyl group at C-6 were the most potent inhibitors. Compound 54, which had IC50 values of 31, 88, and 31 nM against PDGFr, FGFr, and c-src TK activity, respectively, was active in a variety of PDGF-dependent cellular assays and blocked the in vivo growth of three PDGF-dependent tumor lines.