Identification of aminopyrazolopyridine ureas as potent VEGFR/PDGFR multitargeted kinase inhibitors

Tumor angiogenesis is mediated by KDR and other VEGFR and PDGFR kinases. Their inhibition presents an attractive approach for developing anticancer therapeutics. Here, we report a series of aminopyrazolopyridine ureas as potent VEGFR/PDGFR multitargeted kinase inhibitors. A number of compounds have been identified to be orally bioavailable and efficacious in the mouse edema model.     

Arylphthalazines as potent,and orally bioavailable inhibitors of VEGFR-2

A series of arylphthalazine derivatives were synthesized and evaluated as antagonists of VEGF receptor II (VEGFR-2). IM-094482 57, which was prepared in two steps from commercially available starting materials, was found to be a potent inhibitor of VEGFR-2 in enzymatic, cellular and mitogenic assays (comparable activity to ZD-6474). Additionally, 57 inhibited the related receptor, VEGF receptor I (VEGFR-1), and showed excellent exposure when dosed orally to female CD-1 mice.     

A novel chemotype of kinase inhibitors: Discovery of 3,4-ring fused 7-azaindoles and deazapurines as potent JAK2 inhibitors

Pictet–Spengler condensation of aldehydes or alpha-keto-esters with 4-(2-anilinophenyl)-7-azaindole (11) or deazapurine (12) gave high yields of the 3,4-fused cyclic compounds. SAR studies, by varying the substituted benzaldehyde components, lead to the discovery of a series of potent JAK2 kinase inhibitors.     

Triketoacid inhibitors of HIV-integrase: a new chemotype useful for probing the integrase pharmacophore

Integrase is one of three enzymes expressed by HIV and represents a validated target for therapy. This study reports on the discovery of a new triketoacid-based chemotype that selectively inhibits the strand transfer reaction of HIV-integrase. SAR studies showed that the template binds to integrase in a manner similar to the diketoacid-based inhibitors. Moreover, comparison of the new chemotype to two different diketoacid templates led us to propose two aryl-binding domains in the inhibitor binding site. This information was used to design a new diketoacid template with improved activity against the enzyme.     

Identification of potent and selective VEGFR receptor tyrosine kinase inhibitors having new amide isostere headgroups

A novel series of malonamide-type dual VEGFR2/c-Met inhibitors in which one of the amide bonds was replaced by an amide isostere—a trifluoroethylamine unit, was designed, synthesized, and evaluated for their enzymatic and cellular inhibition of VEGFR2 and c-Met enzymes. Optimization of these molecular entities resulted in identification of potent and selective inhibitors of VEGFR2 enzyme.     

Proteomics-based target identification: bengamides as a new class of methionine aminopeptidase inhibitors

LAF389 is a synthetic analogue of bengamides, a class of marine natural products that produce inhibitory effects on tumor growth in vitro and in vivo. A proteomics-based approach has been used to identify signaling pathways affected by bengamides. LAF389 treatment of cells resulted in altered mobility of a subset of proteins on two-dimensional gel electrophoresis. Detailed analysis of one of the proteins, 14-3-3gamma, showed that bengamide treatment resulted in retention of the amino-terminal methionine, suggesting that bengamides directly or indirectly inhibited methionine aminopeptidases (MetAps). Both known MetAps are inhibited by LAF389. Short interfering RNA suppression of MetAp2 also altered amino-terminal processing of 14-3-3gamma. A high resolution structure of human MetAp2 co-crystallized with a bengamide shows that the compound binds in a manner that mimics peptide substrates. Additionally, the structure reveals that three key hydroxyl groups on the inhibitor coordinate the di-cobalt center in the enzyme active site.     

Discovery of heterocyclic ureas as a new class of raf kinase inhibitors: identification of a second generation lead by a combinatorial chemistry approach

Heterocyclic ureas, such as N-3-thienyl N'-aryl ureas, have been identified as novel inhibitors of raf kinase, a key mediator in the ras signal transduction pathway. Structure-activity relationships were established, and the potency of the screening hit was improved 10-fold to IC(50)=1.7 microM. A combinatorial synthesis approach enabled the identification of a breakthrough lead (IC(50)=0.54 microM) for a second generation series of heterocyclic urea raf kinase inhibitors.     

Serotonin derivatives as a new class of non-ATP-competitive receptor tyrosine kinase inhibitors

The discovery of new templates and their subsequent elaboration to clinically useful receptor tyrosine kinase (RTK) inhibitors continues to be an important issue. RTKs are a class of enzymes responsible for the activation of different cellular signal transduction cascades. The majority of the known small molecules RTK inhibitors are ATP-competitive and they are multiple targeted inhibitors. We describe here serotonin derivatives as a new class of multiple targeted RTK inhibitors. In contrast to most other RTK inhibitors they act via a non-ATP-competitive (allosteric) mechanism. Furthermore, they are able to inhibit the proliferation of HUVE cells, fibroblasts and two cancer cell lines.     

Target identification,lead optimization and antitumor evaluation of some new 1,2,4-triazines as c-Met kinase inhibitors

In silico target fishing approach using PharmMapper server identified c-Met kinase as the selective target for our previously synthesized compound NCI 748494/1. This approach was validated by in vitro kinase assay which showed that NCI 748494/1 possessed promising inhibitory activity against c-Met kinase (IC₅₀ = 31.70 μM). Assessment of ADMET profiling, drug-likeness, drug score as well as docking simulation for the binding pose of that compound in the active site of c-Met kinase domain revealed that NCI 748494/1 could be considered as a promising drug lead. Based on target identification and validation, it was observed that there is structure similarity between NCI 748494/1 and the reported type II c-Met kinase inhibitor BMS-777607. Optimization of our lead NCI 748494/1 furnished newly synthesized 1,2,4-triazine derivatives based on well-established structure-activity relationships, whereas three compounds namely; 4d, 7a and 8c displayed excellent in vitro cytotoxicity against three c-Met addicted cancer cell lines; A549 (lung adenocarcinoma), HT-29 (colon cancer) and MKN-45 (gastric carcinoma); with IC₅₀ values in the range 0.01–1.86 µM. In vitro c-Met kinase assay showed 8c to possess the highest c-Met kinase inhibition profile (IC₅₀ = 4.31 µM). Docking of the active compounds in c-Met kinase active site revealed strong binding interactions comparable to the lead NCI 748494/1 and BMS-777607, suggesting that c-Met inhibition is very likely to be the mechanism of the antitumor effect of these derivatives.     

Salicylaldehyde derivatives as new protein kinase CK2 inhibitors

Protein kinase CK2 is a Ser/Thr kinase, with a constitutive activity, that is considered as a promising target for cancer therapy. The currently available CK2 inhibitors lack the potency and the pharmacological properties necessary to be suitable and successful in clinical settings. We report the development of new potent CK2 inhibitors from salicylaldehyde derivatives identified by automated screening of a proprietary small-molecule library. Docking simulations and analysis of the structure-activity relationship for the hits allowed to determine their binding modes on CK2, and to carry out the optimization of their structures. This strategy led to the discovery of potent CK2 inhibitors with novel structures, one of which was able to inhibit CK2 activity in living cells and promote tumor cell death. The essential features required for potent CK2 inhibitory activity of this class of compounds are discussed.     

Discovery of new chemotype dipeptidyl peptidase IV inhibitors having (R)-3-amino-3-methyl piperidine as a pharmacophore

Structures containing the (R)-3-amino-3-methyl piperidine unit as a new pharmacophore moiety have been shown to possess moderate inhibitory activity for DPP-4 with good pharmacokinetics profile. One of these compounds was found to have good oral bioavailability and PK/PD profile in ZF-rat.     

VEGFR2 and Src kinase inhibitors suppress Andes virus-induced endothelial cell permeability

Hantaviruses predominantly infect human endothelial cells and, in the absence of cell lysis, cause two diseases resulting from increased vascular permeability. Andes virus (ANDV) causes a highly lethal acute pulmonary edema termed hantavirus pulmonary syndrome (HPS). ANDV infection enhances the permeability of endothelial cells in response to vascular endothelial growth factor (VEGF) by increasing signaling responses directed by the VEGFR2-Src-VE-cadherin pathway, which directs adherens junction (AJ) disassembly. Here we demonstrate that inhibiting pathway-specific VEGFR2 and Src family kinases (SFKs) blocks ANDV-induced endothelial cell permeability. Small interfering RNA (siRNA) knockdown of Src within ANDV-infected endothelial cells resulted in an ～70% decrease in endothelial cell permeability compared to that for siRNA controls. This finding suggested that existing FDA-approved small-molecule kinase inhibitors might similarly block ANDV-induced permeability. The VEGFR2 kinase inhibitor pazopanib as well as SFK inhibitors dasatinib, PP1, bosutinib, and Src inhibitor 1 dramatically inhibited ANDV-induced endothelial cell permeability. Consistent with their kinase-inhibitory concentrations, dasatinib, PP1, and pazopanib inhibited ANDV-induced permeability at 1, 10, and 100 nanomolar 50% inhibitory concentrations (IC(50)s), respectively. We further demonstrated that dasatinib and pazopanib blocked VE-cadherin dissociation from the AJs of ANDV-infected endothelial cells by >90%. These findings indicate that VEGFR2 and Src kinases are potential targets for therapeutically reducing ANDV-induced endothelial cell permeability and, as a result, capillary permeability during HPS. Since the functions of VEGFR2 and SFK inhibitors are already well defined and FDA approved for clinical use, these findings rationalize their therapeutic evaluation for efficacy in reducing HPS disease. Endothelial cell barrier functions are disrupted by a number of viruses that cause hemorrhagic, edematous, or neurologic disease, and as a result, our findings suggest that VEGFR2 and SFK inhibitors should be considered for regulating endothelial cell barrier functions altered by additional viral pathogens.     

Naphthyl ketones: a new class of Janus kinase 3 inhibitors

Potent inhibition of Janus kinase 3 was found for a series of naphthyl(beta-aminoethyl)ketones (e.g. 7, pIC50 = 7.1+/-0.3). Further studies indicated that these compounds fragment in less than 1 h by retro-Michael reaction in the Jak3 in vitro ELISA assay procedure. The breakdown product of 7, 2-naphthylvinyl ketone (22, pIC50 = 6.8+/-0.3) showed very similar inhibitory activity to 7. Compounds 7 (in neutral buffer) and 22 will be useful pharmacological tools for the investigation of the Janus tyrosine kinase Jak3.     

Pharmacophore identification of Raf-1 kinase inhibitors

A three-dimensional pharmacophore model was developed based on 25 currently available Raf-1 kinase inhibitors. The best pharmacophore hypothesis (Hypo1), consisting of four chemical features (one hydrogen-bond acceptor, one hydrogen-bond donor, and two hydrophobic groups), has a correlation coefficient of 0.972. The results of our study provide a valuable tool in designing new leads with desired biological activity by virtual screening.     

Proteomics identification of sorting nexin 27 as a diacylglycerol kinase zeta-associated protein: new diacylglycerol kinase roles in endocytic recycling

Diacylglycerol kinase zeta is a member of the diacylglycerol kinase family of enzymes, which generate phosphatidic acid through diacylglycerol phosphorylation. In addition to the catalytic and cysteine-rich domains found in all diacylglycerol kinases, diacylglycerol kinase zeta has a MARCKS domain as well as a C-terminal region containing four ankyrin repeats and a PDZ-binding motif. Previous reports demonstrated that diacylglycerol kinase zeta interaction with several proteins is an important mechanism for modulating the localization and activity of this enzyme. Here we used a proteomics approach to search for novel diacylglycerol kinase zeta-interacting proteins and identified sorting nexin 27 (SNX27), a recently described member of a protein family involved in intracellular trafficking, which has a PDZ domain in addition to the phox homology domain characteristic of SNX proteins. Co-immunoprecipitation studies and two-hybrid analysis confirmed physical, PDZ-dependent association between SNX27 and diacylglycerol kinase zeta. Because diacylglycerol kinase zeta is expressed abundantly in T lymphocytes, we characterized SNX27 expression and subcellular localization in these cells. SNX27 co-localized with transferrin receptor-positive vesicles, pointing to its participation in T cell endocytic recycling. Expression of deletion mutants revealed that in addition to the phox homology domain the SNX27 PDZ domain contributed to vesicle localization of this protein, suggesting that interaction with diacylglycerol kinase zeta regulates SNX27 localization. Analysis of cells with RNA interference-mediated knockdown of diacylglycerol kinase zeta showed accelerated transferrin receptor exit from the lymphocyte endocytic recycling compartment back to the plasma membrane, further confirming diacylglycerol kinase zeta-dependent control of vesicle trafficking. These data support a previously unreported role for diacylglycerol kinase zeta in the modulation of membrane trafficking, which may also help to define SNX27 function.     

Discovery of a novel and potent series of dianilinopyrimidineurea and urea isostere inhibitors of VEGFR2 tyrosine kinase

A series of dianilinopyrimidineureas demonstrate potency as VEGFR2 kinase inhibitors.     

Comparative molecular field analysis (CoMFA) of phthalazine derivatives as phosphodiesterase IV inhibitors

A comparative molecular field analysis (CoMFA) of phthalazine class of phosphodiesterase IV (PDE IV) inhibitors has been performed to correlate their chemical structures with their observed biological activity. A statistically valid model with good correlative and predictive power is reported. The leave one out cross-validation study gave cross-validation r(2)(cv) of value 0.507 at six optimum components and conventional r(2) of value 0.98. The predictive ability of the model was tested by predicting the seven molecules belonging to the test set giving predictive correlation coefficient of 0.59. This model is potentially helpful in the design of novel and more potent PDE IV inhibitors.     

Substituted benzimidazoles: A novel chemotype for small molecule hKSP inhibitors

Substituted benzimidazoles were profiled as inhibitors of kinesin spindle protein (KSP), an increasingly important target for the development of anticancer drugs. This series demonstrated the monoastral phenotypic response and was found to be active in both enzymatic and cellular-based assays.     

Discovery of a new class of p38 kinase inhibitors

The MAP kinase p38 has been implicated in cytokine signaling, and its inhibitors are potentially useful for the treatment of arthritis and osteoporosis. Novel small-molecule inhibitors of p38 kinase were derived from a combinatorial chemistry effort and exhibit activity in the nanomolar range. Very steep structure-activity relationships are observed within this class.