Synthesis and biological evaluation of 2,4-disubstituted phthalazinones as Aurora kinase inhibitors

A series of 2,4-disubstituted phthalazinones were synthesized and their biological activities, including antiproliferation, inhibition against Aurora kinases and cell cycle effects were evaluated. Among them, N-cyclohexyl-4-((4-(1-methyl-1H-pyrazol-4-yl)-1-oxophthalazin-2(1H)-yl) methyl) benzamide (12c) exhibited the most potent antiproliferation against five carcinoma cell lines (HeLa, A549, HepG2, LoVo and HCT116 cells) with IC₅₀ values in range of 2.2–4.6?μM, while the IC₅₀ value of reference compound VX-680 was 8.5–15.3?μM. Moreover, Aurora kinase assays exhibited that compound 12c was potent inhibitor of AurA and AurB kinase with the IC₅₀ values were 118?±?8.1 and 80?±?4.2?nM, respectively. Molecular docking studies indicated that compound 12c forms better interaction with both AurA and AurB. Furthermore, compound 12c induced G2/M cell cycle arrest in HeLa cells by regulating protein levels of cyclinB1 and cdc2. These results suggested that 12c is a promising pan-Aurora kinase inhibitor for the potential treatment of cancer.     

Synthesis and biological evaluation of nitroxide labeled pyrimidines as Aurora kinase inhibitors

To find novel effective Aurora kinases inhibitors, a series of structurally interesting nitroxide labeled pyrimidines were synthesized and evaluated their anti-proliferative and Aurora kinases inhibitory activities. Among them, butyl 2-(3-((5-fluoro-2-((4-((1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl)carbamoyl) phenyl) amino)pyrimidin-4-yl)amino)-1H-pyrazol-5-yl)acetate (22) possessed the most potent anti-proliferative effects against four carcinoma cell lines with IC₅₀ values in range of 0.89–11.41?μM, and kinases inhibition against Aurora A and B with the IC₅₀ values were 9.3 and 2.8?nM, respectively. Furthermore, compound 22 blocked the phosphorylation of Aurora A (T288), Aurora B (Thr232) and HisH3, decreased the expression of proteins TPX2, Eg5 and Bora, as well as disrupted the mitotic spindle formation in HeLa cells. Molecular docking studies indicated that compound 22 well interact with both Aurora A and B. The results showed that compound 22 is a potential anticancer agent as promising pan-Aurora kinase inhibitor.     

Optimization and biological evaluation of nicotinamide derivatives as Aurora kinase inhibitors

Aurora kinases are known to be overexpressed in various solid tumors and implicated in oncogenesis and tumor progression. A series of nicotinamide derivatives were synthesized and their biological activities were evaluated, including kinase inhibitory activity against Aur A and Aur B and in vitro antitumor activity against SW620, HT-29, NCI-H1975 and Hela cancer cell lines. In addition, the study of antiproliferation, cytotoxicity and apoptosis was performed meanwhile. As the most potent inhibitor of Aur A, 4-((3-bromo-4-fluorophenyl)amino)-6-chloro-N-(4-((6,7-dimethoxyquinolin-4-yl)oxy)-3-fluorophenyl)nicotinamide (10l) showed excellent antitumor activity against SW620 and NCI-H1975 with IC₅₀ values were 0.61 and 1.06 μM, while the IC₅₀ values of reference compound were 3.37 and 6.67 μM, respectively. Furthermore, binding mode studies indicated that compound 10l forms better interaction with Aur A.     

Fluorinated indazoles as novel selective inhibitors of nitric oxide synthase (NOS): Synthesis and biological evaluation

In order to find new compounds with neuroprotective activity and NOS-I/NOS-II selectivity, we have designed, synthesized, and characterized 14 new NOS inhibitors with an indazole structure. The first group corresponds to 4,5,6,7-tetrahydroindazoles (4–8), the second to the N-methyl derivatives (9–12) of 7-nitro-1H-indazole (1) and 3-bromo-7-nitro-1H-indazole (2), and the latter to 4,5,6,7-tetrafluoroindazoles (13–17). Compound 13 (4,5,6,7-tetrafluoro-3-methyl-1H-indazole) inhibited NOS-I by 63% and NOS-II by 83%. Interestingly, compound 16 (4,5,6,7-tetrafluoro-3-perfluorophenyl-1H-indazole) inhibited NOS-II activity by 80%, but it did not affect to NOS-I activity. Structural comparison between these new indazoles further supports the importance of the aromatic indazole skeleton for NOS inhibition and indicate that bulky groups or N-methylation of 1 and 2 diminish their effect on NOS activity. The fluorination of the aromatic ring increased the inhibitory potency and NOS-II selectivity, suggesting that this is a promising strategy for NOS selective inhibitors.     

Synthesis and evaluation of pyrido-thieno-pyrimidines as potent and selective Cdc7 kinase inhibitors

Cdc7 kinase plays a critical role in the regulation of DNA replication in eukaryotic cells and has been proposed as a target for cancer therapy. We have identified a class of Cdc7/Dbf4 inhibitors with a pyrido-thieno-pyrimidine core structure. Synthesis of a focused pyrido-thieno-pyrimidine library yielded potent and selective Cdc7 inhibitors with antiproliferative activity against cancer cells in vitro. Their synthesis and SAR data are presented herein.     

Discovery of indazoles as inhibitors of Tpl2 kinase

Synthesis, modeling and structure-activity relationship of indazoles as inhibitors of Tpl2 kinase are described. From a high throughput screening effort, we identified an indazole hit compound 5 that has a single digit micromolar Tpl2 activity. Through SAR modifications at the C3 and C5 positions of the indazole, we discovered compound 31 with good potency in LANCE assay and cell-based p-Erk assay.     

2-Aminobenzimidazoles as potent Aurora kinase inhibitors

This Letter describes the discovery and key structure–activity relationship (SAR) of a series of 2-aminobenzimidazoles as potent Aurora kinase inhibitors. 2-Aminobenzimidazole serves as a bioisostere of the biaryl urea residue of SNS-314 (1c), which is a potent Aurora kinase inhibitor and entered clinical testing in patients with solid tumors. Compared to SNS-314, this series of compounds offers better aqueous solubility while retaining comparable in vitro potency in biochemical and cell-based assays; in particular, 6m has also demonstrated a comparable mouse iv PK profile to SNS-314.     

Exploration of diverse hinge-binding scaffolds for selective Aurora kinase inhibitors

Four hinge-binding scaffolds have been explored for novel selective Aurora kinase inhibitors. The structure activity relationship, selectivity and pharmacokinetic profiles have been evaluated.     

Discovery and optimization of indazoles as potent and selective interleukin-2 inducible T cell kinase (ITK) inhibitors

There is evidence that small molecule inhibitors of the non-receptor tyrosine kinase ITK, a component of the T-cell receptor signaling cascade, could represent a novel asthma therapeutic class. Moreover, given the expected chronic dosing regimen of any asthma treatment, highly selective as well as potent inhibitors would be strongly preferred in any potential therapeutic. Here we report hit-to-lead optimization of a series of indazoles that demonstrate sub-nanomolar inhibitory potency against ITK with strong cellular activity and good kinase selectivity. We also elucidate the binding mode of these inhibitors by solving the X-ray crystal structures of the complexes.     

Synthesis and evaluation of pyrazolo[1,5-b]pyridazines as selective cyclin dependent kinase inhibitors

A novel series of pyrazolo[1,5-b]pyridazines have been synthesized and identified as cyclin dependant kinase inhibitors potentially useful for the treatment of solid tumors. Modification of the hinge-binding amine or the C(2)- and C(6)-substitutions on the pyrazolopyridazine core provided potent inhibitors of CDK4 and demonstrated enzyme selectivity against VEGFR-2 and GSK3beta.     

Synthesis and evaluation of triazolones as checkpoint kinase 1 inhibitors

Checkpoint kinase 1 (Chk1, CHEK1) is a Ser/Thr protein kinase that plays a key role in mediating the cellular response to DNA-damage. Synthesis and evaluation of a previously described class of Chk1 inhibitors, triazoloquinolones/triazolones (TZs) is further described herein. Our investigation of structure-activity relationships led to the identification of potent inhibitors 14c, 14h and 16e. Key challenges included modulation of physicochemical properties and pharmacokinetic (PK) parameters to enable compound testing in a Chk1 specific hollow fiber pharmacodynamic model. In this model, 16e was shown to abrogate topotecan-induced cell cycle arrest in a dose dependent manner. The demonstrated activity of TZs in this model in combination with a chemotherapeutic agent as well as radiotherapy validates this series of Chk1 inhibitors. X-ray crystal structures (PDB code: 2YEX and 2YER) for an initial lead and an optimized analog are also presented.     

Discovery of novel 2,4-disubstituted pyrimidines as Aurora kinase inhibitors

In order to explore novel Aurora kinase inhibitors, a series of novel 2,4-disubstituted pyrimidines were designed, synthesized and evaluated their in vitro anti-proliferative activities against a panel of cancerous cell lines (A549, HCT-116 and MCF-7). Among them, compound 12a showed the moderate to high anti-proliferative activities against A549 (IC₅₀ = 12.05 ± 0.45 μM), HCT-116 (IC₅₀ = 1.31 ± 0.41 μM) and MCF-7 (IC₅₀ = 20.53 ± 6.13 μM) cells, as well as the Aurora A and Aurora B inhibitory activities with the IC₅₀ values of 309 nM and 293 nM, respectively. Furthermore, compound 12a induced apoptosis by upregulated the pro-apoptotic proteins Bax and decreased the anti-apoptotic protein Bcl-xl in HCT-116 cells. Moreover, the molecular docking study showed that compound 12a had good binding modes with Aurora A and Aurora B and the bioinformatics prediction discovered that compound 12a exhibited good drug likeness using SwissADME. Taken together, these results indicated that 12a may be a potential anticancer compound that was worthy of further development as Aurora kinase inhibitor.     

Synthesis and activity of quinolinyl-methylene-thiazolinones as potent and selective cyclin-dependent kinase 1 inhibitors

A novel series of quinolinyl-methylene-thiazolinones has been identified as potent and selective cyclin-dependent kinase 1 (CDK1) inhibitors. Their synthesis and structure activity relationships (SAR) are described. Representative compounds from this class reversibly inhibit CDK1 activity in vitro, and block cell cycle progression in human tumor cell lines, suggesting a potential use as antitumor agents.     

Synthesis and in vitro anticancer evaluation of some fused indazoles,quinazolines and quinolines as potential EGFR inhibitors

derivatives of benzo[g]indazole 5a, b, benzo[h]quinazoline 7, 12a-c, 13a-c and 15a-c and benzo[h]quinoline 17a-c and 19a-c were synthesized from 6-methoxy-3,4-dihydronaphthalen-1(2H)-one (1). Anticancer activity of all the synthesized compounds was evaluated against four cancerous cell lines; HepG2, MCF-7, HCT116 and Caco-2. MCF-7 cells emerged as the most sensitive cell line against the target compounds. All the examined compounds, except 5a and 5b, displayed potent to moderate anticancer activity against MCF-7 cells with an IC₅₀ values ranging from 7.21 to 21.55 µM. In particular, compounds 15c and 19b emerged as the most potent derivatives against EGFR-expressing MCF-7 cells with IC₅₀ values = 7.70 ± 0.39 and 7.21 ± 0.43 μM, respectively. Additionally, both compounds did not display any significant cytotoxicity towards normal BHK-21 fibroblast cells (IC₅₀ value > 200 µM), thereby providing a good safety profile as anticancer agents. Furthermore, compounds 15c and 19b displayed potent inhibitory activity towards EGFR in the sub-micromolar range (IC₅₀ = 0.13 ± 0.01 and 0.14 ± 0.01 μM, respectively), compared to that of Erlotinib (IC₅₀ = 0.11 ± 0.01 μM). Docking studies for 15c and 19b into EGFR active site was carried out to explore their potential binding modes. Therefore, compounds 15c and 19b can be considered as interesting candidates for further development of more potent anticancer agents.     

Synthesis and biological evaluation of 4-quinazolinones as Rho kinase inhibitors

Rho kinase (ROCK) is an attractive therapeutic target for various diseases including glaucoma, hypertension, and spinal cord injury. Herein, we report the development of a series of ROCK-II inhibitors based on 4-quinazolinone and quinazoline scaffolds. SAR studies at three positions of the quinazoline core led to the identification of analogs with high potency against ROCK-II and good selectivity over protein kinase A (PKA).     

Synthesis and biological evaluation of 3,5-diaminoindazoles as cyclin-dependent kinase inhibitors

A novel series of 3,5-diaminoindazoles were prepared and found to be CDK inhibitors. Potent inhibitors against CDK1 and CDK2 were obtained by introduction of 1lambda(6)-isothiazolidine-1,1-dioxide at 5-position of indazole. Anti-proliferative activities of compounds were evaluated using EJ, HCT116, SW620, and A549 cancer cell lines.     

Identification of pyrrolo[2,3-g]indazoles as new Pim kinase inhibitors

The synthesis and Pim kinase inhibition potency of a new series of pyrrolo[2,3-g]indazole derivatives is described. The results obtained in this preliminary structure–activity relationship study pointed out that sub-micromolar Pim-1 and Pim-3 inhibitory potencies could be obtained in this series, more particularly for compounds 10 and 20, showing that pyrrolo[2,3-g]indazole scaffold could be used for the development of new potent Pim kinase inhibitors. Molecular modeling experiments were also performed to study the binding mode of these compounds in Pim-3 ATP-binding pocket.     

Synthesis and SAR of 1-acetanilide-4-aminopyrazole-substituted quinazolines: selective inhibitors of Aurora B kinase with potent anti-tumor activity

A new class of 1-acetanilide-4-aminopyrazole-substituted quinazoline Aurora kinase inhibitors has been discovered possessing highly potent cellular activity. Continuous infusion into athymic mice bearing SW620 tumors of the soluble phosphate derivative 2 led to dose-proportional exposure of the des-phosphate compound 8 with a high-unbound fraction. The combination of potent cell activity and high free-drug exposure led to pharmacodynamic changes in the tumor at low doses, indicative of Aurora B-kinase inhibition and a reduction in tumor volume.     

Thienopyridine ureas as dual inhibitors of the VEGF and Aurora kinase families

In an effort to identify multi-targeted kinase inhibitors with a novel spectrum of kinase activity, a screen of Abbott proprietary KDR inhibitors against a broad panel of kinases was conducted and revealed a series of thienopyridine ureas with promising activity against the Aurora kinases. Modification of the diphenyl urea and C7 moiety of these compounds provided potent inhibitors with good pharmacokinetic profiles that were efficacious in mouse tumor models after oral dosing. Compound 2 (ABT-348) of this series is currently undergoing Phase I clinical trials in solid and hematological cancer populations.     

Synthesis and biological evaluation of quinoxaline derivatives as specific c-Met kinase inhibitors

A series of novel quinoxaline derivatives were synthesized and evaluated for their inhibitory activity against c-Met kinase enzyme. Most of the tested compounds exhibited potent inhibitory activity. All the synthesized quinoxaline compounds were further examined against c-Met overexpressed human gastric cancer cell line (MKN-45), which showed good inhibitory activity. Among the synthesized compounds, compound 4 exhibited better tumor growth inhibition in the animal model study; we also confirmed its acceptable drug property and highly selective target activity.