N-(Aryl)-4-(azolylethyl)thiazole-5-carboxamides: novel potent inhibitors of VEGF receptors I and II

Novel potent derivatives of N-(aryl)-4-(azolylethyl)thiazole-5-carboxamides are described as inhibitors of vascular endothelial growth factor receptor II (VEGFR-2). Several compounds display VEGFR-2 inhibitory activity reaching IC(50)<100 nM in both enzymatic and cellular assays. The compounds also inhibit the related tyrosine kinase, VEGFR-1. By controlling the substitution pattern on the 5-carboxamido pharmacophore, both dual and specific VEGFR-2 thiazoles were identified.     

Exploration of acridine scaffold as a potentially interesting scaffold for discovering novel multi-target VEGFR-2 and Src kinase inhibitors

VEGFR-2 and Src kinases both play important roles in cancers. In certain cancers, Src works synergistically with VEGFR-2 to promote its activation. Development of multi-target drugs against VEGFR-2 and Src is of therapeutic advantage against these cancers. By using molecular docking and SVM virtual screening methods and based on subsequent synthesis and bioassay studies, we identified 9-aminoacridine derivatives with an acridine scaffold as potentially interesting novel dual VEGFR-2 and Src inhibitors. The acridine scaffold has been historically used for deriving topoisomerase inhibitors, but has not been found in existing VEGFR-2 inhibitors and Src inhibitors. A series of 21 acridine derivatives were synthesized and evaluated for their antiproliferative activities against K562, HepG-2, and MCF-7 cells. Some of these compounds showed better activities against K562 cells in vitro than imatinib. The structure-activity relationships (SAR) of these compounds were analyzed. One of the compounds (7r) showed low μM activity against K562 and HepG-2 cancer cell-lines, and inhibited VEGFR-2 and Src at inhibition rates of 44% and 8% at 50μM, respectively, without inhibition of topoisomerase. Moreover, 10μM compound 7r could reduce the levels of activated ERK1/2 in a time dependant manner, a downstream effector of both VEGFR-2 and Src. Our study suggested that acridine scaffold is a potentially interesting scaffold for developing novel multi-target kinase inhibitors such as VEGFR-2 and Src dual inhibitors.     

Synthesis and anti-tumor activity of [1,4] dioxino [2,3-f] quinazoline derivatives as dual inhibitors of c-Met and VEGFR-2

Both c-Met and VEGFR-2 were important targets for cancer therapies. In order to develop reversible and non-covalent c-Met and VEGFR-2 dual inhibitors, a series of [1,4]dioxino[2,3-f]quinazoline derivatives were designed and synthesized. The enzyme assay demonstrated that most target compounds had inhibition potency on both c-Met and VEGFR-2 with IC₅₀ values in nanomolar range especially compounds 7m and 7k. Based on further cell proliferation assay in vitro, compound 7k showed significantly anti-tumor activity in vivo on a hepatocellular carcinoma (MHCC97H cells) xenograft mouse model. We docked the compound 7m with c-Met and VEGFR-2 kinases, and interpreted the SAR of these analogues. All results indicated that the target compounds were dual inhibitors of c-Met and VEGFR-2 kinases that held promising potential in cancer therapy.     

(1,2,3-Triazol-4-yl)benzenamines: Synthesis and activity against VEGF receptors 1 and 2

Derivatives of (1,2,3-triazol-4-yl)benzenamines are described as potent and ATP-competitive inhibitors of vascular endothelial growth factor receptors I and II (VEGFR-1/2). A number of compounds exhibited VEGFR-2 and VEGFR-1 inhibitory activity comparable to that of Vatalanib? in both HTRF enzymatic and cellular assays.     

De novo design of VEGFR-2 tyrosine kinase inhibitors based on a linked-fragment approach

Vascular endothelial growth factor receptor-2 (VEGFR-2) tyrosine kinase inhibitors have been demonstrated to possess substantial antitumor activity. VEGFR-2 tyrosine kinase inhibitors are crucial for development of antitumor drugs. Based on the crystal structure of VEGFR-2 tyrosine kinase, a linked-fragment strategy was employed to design novel VEGFR-2 tyrosine kinase inhibitors, and 1000 compounds were generated in this process. Absorption, distribution, metabolism, excretion and toxicity (ADMET) were used to screen the 1000 compounds, and 59 compounds were acceptable. Scaffold hopping was then used for further screening, and only four compounds were obtained in this way. Then, the binding energy of the four molecules to VEGFR-2 tyrosine kinase was calculated using molecular docking, and their values were found to be lower than that of Sorafenib. Finally, molecular dynamics simulations were performed on the complex of the compound with the lowest binding energy with VEGFR-2 tyrosine kinase, and the binding model was analyzed. At the end, four chemical entities with novel structures were obtained, and were suggested for experimental testing in future studies.     

Identification of new pyrrolo[2,3-d]pyrimidines as potent VEGFR-2 tyrosine kinase inhibitors: Design,synthesis, biological evaluation and molecular modeling

Vascular endothelial growth factor receptor-2 (VEGFR-2) plays a crucial role in cancer angiogenesis. In the current study, a series of novel pyrrolo[2,3-d]pyrimidine based-compounds was designed and synthesized as VEGFR-2 inhibitors, in accordance to the structure activity relationship (SAR) studies of known type II VEGFR-2 inhibitors. The newly synthesized compounds were evaluated for their ability to inhibit VEGFR-2 kinase enzyme in vitro. All the tested compounds demonstrated highly potent dose-related VEGFR-2 inhibition with IC₅₀ values in nanomolar range. Among these compounds, pyrrolo[2,3-d]pyrimidine derivatives carrying biaryl urea moieties (12d and 15c) exhibited IC₅₀ values of 11.9 and 13.6 nM respectively. Additionally, most of the newly synthesized final compounds were tested on 60 human cancer cell lines. Docking of these compounds into the inactive conformation of VEGFR-2 was performed which showed comparable binding modes to that of the FDA approved VEGFR-2 kinase inhibitors. These newly discovered potent kinase inhibitors could be considered as potential candidates for the development of new targeted anticancer agent.     

Design,synthesis and biological evaluation of type-II VEGFR-2 inhibitors based on quinoxaline scaffold

In an effort to develop ATP-competitive VEGFR-2 selective inhibitors, a series of new quinoxaline-based derivatives was designed and synthesized. The target compounds were biologically evaluated for their inhibitory activity against VEGFR-2. The design of the target compounds was accomplished after a profound study of the structure activity relationship (SAR) of type-II VEGFR-2 inhibitors. Among the synthesized compounds, 1-(2-((4-methoxyphenyl)amino)-3-oxo-3,4 dihydroquinoxalin-6-yl)-3-phenylurea (VIIa) displayed the highest inhibitory activity against VEGFR-2. Molecular modeling study involving molecular docking and field alignment was implemented to interpret the variable inhibitory activity of the newly synthesized compounds.     

2-((1H-Azol-1-yl)methyl)-N-arylbenzamides: novel dual inhibitors of VEGFR-1/2 kinases

Novel potent derivatives of (azol-1-yl)methyl-N-arylbenzamides with improved solubility (>3mM) are described as ATP-competitive inhibitors of vascular endothelial growth factor receptor 2 (VEGFR-2). Many compounds display VEGFR-2 inhibitory activity reaching IC(50)<100 nM in the enzymatic assay. The compounds also inhibit the related tyrosine kinase, VEGFR-1, with similar potencies. Several compounds containing bulky lipophilic substituents at the benzamide pharmacophore yielded 10- to 17-fold selectivity for the VEGFR-2 versus VEGFR-1 kinase.     

1,3,4-Oxadiazole-naphthalene hybrids as potential VEGFR-2 inhibitors: design,synthesis, antiproliferative activity,apoptotic effect,and in silico studies

In the current work, some 1,3,4-oxadiazole-naphthalene hybrids were designed and synthesised as VEGFR-2 inhibitors. The synthesised compounds were evaluated in vitro for their antiproliferative activity against two human cancer cell lines namely, HepG-2 and MCF-7. Compounds that exhibited promising cytotoxicity (5, 8, 15, 16, 17, and 18) were further evaluated for their VEGFR-2 inhibitory activities. Compound 5 showed good antiproliferative activity against both cell lines and inhibitory effect on VEGFR-2. Besides, it induced apoptosis by 22.86% compared to 0.51% in the control (HepG2) cells. This apoptotic effect was supported by a 5.61-fold increase in the level of caspase-3 compared to the control cells. Moreover, it arrested the HepG2 cell growth mostly at the Pre-G1 phase. Several in silico studies were performed including docking, ADMET, and toxicity studies to predict binding mode against VEGFR-2 and to anticipate pharmacokinetic, drug-likeness, and toxicity of the synthesised compounds.     

Discovery of benzimidazole derivatives as novel multi-target EGFR, VEGFR-2 and PDGFR kinase inhibitors

Multi-target EGFR, VEGFR-2 and PDGFR inhibitors are highly useful anticancer agents with improved therapeutic efficacies. In this work, we used two virtual screening methods, support vector machines (SVM) and molecular docking, to identify a novel series of benzimidazole derivatives, 2-aryl benzimidazole compounds, as multi-target EGFR, VEGFR-2 and PDGFR inhibitors. 2-Aryl benzimidazole compounds were synthesized and their biological activities against a tumor cell line HepG-2 and specific kinases were evaluated. Among these compounds, compounds 5a and 5e exhibited high cytotoxicity against HepG-2 cells with IC?? values at ～2 μM. Further kinase assay study showed that compound 5a have good EGFR inhibitory activity and moderate VEGFR-2 and PDGFR inhibitory activities, while 5e have moderate EGFR inhibitory activity and slightly weaker VEGFR-2 and PDGFR inhibitory activities. Molecular docking analysis suggested that compound 5a more tightly interacts with EGFR and PDGFR than compound 5e. Our study discovered a novel series of benzimidazole derivatives as multi-target EGFR, VEGFR-2 and PDGFR kinases inhibitors.     

Design,synthesis, docking,ADMET studies,and anticancer evaluation of new 3-methylquinoxaline derivatives as VEGFR-2 inhibitors and apoptosis inducers

Vascular endothelial growth factor receptor-2 (VEGFR-2) plays a critical role in cancer angiogenesis. Inhibition of VEGFR-2 activity proved effective suppression of tumour propagation. Accordingly, two series of new 3-methylquinoxaline derivatives have been designed and synthesised as VEGFR-2 inhibitors. The synthesised derivatives were evaluated in vitro for their cytotoxic activities against MCF-7and HepG2 cell lines. In addition, the VEGFR-2 inhibitory activities of the target compounds were estimated to indicate the potential mechanism of their cytotoxicity. To a great extent, the results of VEGFR-2 inhibition were highly correlated with that of cytotoxicity. Compound 27a was the most potent VEGFR-2 inhibitor with IC₅₀ of 3.2 nM very close to positive control sorafenib (IC₅₀ = 3.12 nM). Such compound exhibited a strong cytotoxic effect against MCF-7 and HepG2, respectively with IC₅₀ of 7.7 and 4.5 µM in comparison to sorafenib (IC₅₀ = 3.51 and 2.17 µM). In addition, compounds 28, 30f, 30i, and 31b exhibited excellent VEGFR-2 inhibition activities (IC₅₀ range from 4.2 to 6.1 nM) with promising cytotoxic activity. Cell cycle progression and apoptosis induction were investigated for the most active member 27a. Also, the effect of 27a on the level of caspase-3, caspase-9, and BAX/Bcl-2 ratio was determined. Molecular docking studies were implemented to interpret the binding mode of the target compounds with the VEGFR-2 pocket. Furthermore, toxicity and ADMET calculations were performed for the synthesised compounds to study their pharmacokinetic profiles     

Dual irreversible kinase inhibitors: quinazoline-based inhibitors incorporating two independent reactive centers with each targeting different cysteine residues in the kinase domains of EGFR and VEGFR-2

A series of 4-dimethylamino-but-2-enoic acid [4-(3,6-dioxo-cyclohexa-1,4-dienylamino)-7-ethoxy-quinazolin-6-yl]-amide derivatives were prepared. These compounds have two independent reactive centers and were designed to function as dual irreversible inhibitors of the kinase domains of both Epidermal Growth Factor Receptor (EGFR) and Vascular Endothelial Growth Factor Receptor-2 (VEGFR-2) where each reactive center targets a different, non-conserved, cysteine residue located in the ATP binding pocket of these enzymes. The compounds contain a 6-(4-(dimethylamino) crotonamide) Michael acceptor group that targets Cys-773 in EGFR and a 4-(amino-[1,4]benzoquinone) moiety that targets Cys-1045 in VEGFR-2. In vitro studies indicated that most of these compounds are relatively potent inhibitors of each enzyme. These inhibitors were compared with reference compounds that lack one or both of the reactive centers. The relative dependence of the IC(50) values on the concentration of ATP used in the assays suggests that these compounds appear to function as irreversible inhibitors of each kinase.     

N⁴-Aryl-6-substitutedphenylmethyl-7H-pyrrolo[2,3-d]pyrimidine-2,4-diamines as receptor tyrosine kinase inhibitors

Six novel N(4)-substitutedphenyl-6-substitutedphenylmethyl-7H-pyrrolo[2,3-d]pyrimidine-2,4-diamines were synthesized as multiple receptor tyrosine kinase (RTK) inhibitors and antitumor agents. An improvement in the inhibitory potency against epidermal growth factor receptor (EGFR), vascular endothelial growth factor receptor 1 (VEGFR-1) and vascular endothelial growth factor receptor 2 (VEGFR-2) assays and in the A431 cellular proliferation assay was observed for compounds 8-13 over the previously reported 5-7. Three compounds (8, 9 and 13) demonstrated potent, multiple RTK inhibition and were more potent or equipotent compared to the lead compounds 5 and 7 and the standard compounds. Compounds 10 and 12 showed potent inhibition of VEGFR-2 over EGFR, platelet-derived growth factor receptor-β (PDGFR-β) and VEGFR-1. The results indicate that the RTK inhibitory profile could be modulated with slight variations to the N(4)-aryl-6-substitutedphenylmethyl-7H-pyrrolo[2,3-d]pyrimidine-2,4-diamino scaffold.     

Discovery and molecular docking of quinolyl-thienyl chalcones as anti-angiogenic agents targeting VEGFR-2 tyrosine kinase

Vascular endothelial growth factor Receptor-2 (VEGFR-2) kinase inhibition is one of the well established strategies to promptly tackle tumor growth by suppression of angiogenesis. In the current study, structure-based virtual screening methodology of a series of quinolyl-thienyl chalcones indicated their strong potential as VEGFR-2 kinase inhibitors. In vitro VEGFR-2 kinase inhibitory activity was found to be significant (compound 19, IC(50): 73.41nM). All compounds showed significant inhibition of human umbilical vein endothelial cells (HUVEC) proliferation (compound 19, IC(50): 21.78nM). Molecular interactions of the compounds were studied using molecular docking studies.     

Arylphthalazines. Part 2: 1-(Isoquinolin-5-yl)-4-arylamino phthalazines as potent inhibitors of VEGF receptors I and II

A novel class of 1-(isoquinolin-5-yl)-4-arylamino-phthalazines is described as inhibitors of vascular endothelial growth factor receptor II (VEGFR-2). Many compounds display VEGFR-2 inhibitory activity with an IC(50) as low as 0.017 microM in an HTRF enzymatic assay. The compounds also inhibit VEGFR-1, a related tyrosine kinase.     

Discovery of new nicotinamides as apoptotic VEGFR-2 inhibitors: virtual screening,synthesis, anti-proliferative,immunomodulatory, ADMET,toxicity, and molecular dynamic simulation studies

A library of modified VEGFR-2 inhibitors was designed as VEGFR-2 inhibitors. Virtual screening was conducted for the hypothetical library using in silico docking, ADMET, and toxicity studies. Four compounds exhibited high in silico affinity against VEGFR-2 and an acceptable range of the drug-likeness. These compounds were synthesised and subjected to in vitro cytotoxicity assay against two cancer cell lines besides VEGFR-2 inhibitory determination. Compound D-1 showed cytotoxic activity against HCT-116 cells almost double that of sorafenib. Compounds A-1, C-6, and D-1 showed good IC₅₀ values against VEGFR-2. Compound D-1 markedly increased the levels of caspase-8 and BAX expression and decreased the anti-apoptotic Bcl-2 level. Additionally, compound D-1 caused cell cycle arrest at pre-G1 and G2-M phases in HCT-116 cells and induced apoptosis at both early and late apoptotic stages. Compound D-1 decreased the level of TNF-α and IL6 and inhibited TNF-α and IL6. MD simulations studies were performed over 100 ns.     

Synthesis and evaluation of heteroaryl-ketone derivatives as a novel class of VEGFR-2 inhibitors

We have discovered novel inhibitors of VEGFR-2 kinase with low nanomolar potency in both enzymatic and cell-based assays. Active series are heteroaryl-ketone compounds containing a central aromatic ring with either an indazolyl or indolyl keto group in the ortho orientation to the benzylic amine group (Fig. 1). The best compounds were demonstrated to be inactive against a small select panel of tyrosine and serine/threonine kinases with the exception of VEGFR-1 kinase, a close family member. In addition, the lead candidate 8 displayed acceptable exposure levels when administered orally to mice.     

ortho-Substituted azoles as selective and dual inhibitors of VEGF receptors 1 and 2

We have developed a series of novel potent ortho-substituted azole derivatives active against kinases VEGFR-1 and VEGFR-2. Both specific and dual ATP-competitive inhibitors of VEGFR-2 were identified. Kinase activity and selectivity could be controlled by varying the arylamido substituents at the azole ring. The most specific molecule (17) displayed > 10-fold selectivity for VEGFR-2 over VEGFR-1. Compound activities in enzymatic and cell-based assays were in the range of activities for reported clinical and development candidates (IC50 < 100 nM), including Novartis' PTK787 (Vatalanib). High permeability of active compounds across the Caco-2 cell monolayer (> 30x10(-5) cm/min) is indicative of their potential for intestinal absorption upon oral administration.     

Design and synthesis of 3-(4,5,6,7-tetrahydro-3H-imidazo[4,5-c]pyridin-2-yl)-1H-quinolin-2-ones as VEGFR-2 kinase inhibitors

A series of 3-(4,5,6,7-tetrahydro-3H-imidazo[4,5-c]pyridin-2-yl)-1H-quinolin-2-ones have been identified as a new class of VEGFR-2 kinase inhibitors. A variety of (4,5,6,7-tetrahydro-imidazo[5,4-c]pyridin-2-yl)-acetic acid ethyl esters were synthesized, and their VEGFR-2 inhibitory activity was evaluated. Described herein are the preparation of the series and the effects of the compounds on VEGFR-2 kinase activity.     

Design,synthesis, molecular modeling and biological evaluation of novel Benzoxazole-Benzamide conjugates via a 2-Thioacetamido linker as potential anti-proliferative agents,VEGFR-2 inhibitors and apoptotic inducers

A novel series of 2-thioacetamide linked benzoxazole-benzamide conjugates 1–15 was designed as potential inhibitors of the vascular endothelial growth factor receptor-2 (VEGFR-2). The prepared compounds were evaluated for their potential antitumor activity and their corresponding selective cytotoxicity was estimated using normal human fibroblast (WI-38) cells. Compounds 1, 9–12 and 15 showed good selectivity and displayed excellent cytotoxic activity against both HCT-116 and MCF-7 cancer cell lines compared to sorafenib, used as a reference compound. Furthermore, compounds 1 and 11 showed potent VEGFR-2 inhibitory activity. The cell cycle progression assay showed that 1 and 11 induced cell cycle arrest at G2/M phase, with a concomitant increase in the pre-G1 cell population. Further pharmacological studies showed that 1 and 11 induced apoptosis and inhibited the expression of the anti-apoptotic Bcl-2 and Bcl-xL proteins in both cell lines. Therefore, compounds 1 and 11 might serve as promising candidates for future anticancer therapy development.