3-Cyano-6-(5-methyl-3-pyrazoloamino)pyridines: Selective Aurora A kinase inhibitors

A new class of Aurora A kinase inhibitor was created by transforming 4-(5-methyl-3-pyrazoloamino)pyrimidine moiety of VX-680 to 3-cyano-6-(5-methyl-3pyrazoloamino)pyridine. Compound 6 exhibited a potent Aurora A kinase inhibitory activity, excellent selectivity to Aurora B kinase and other 60 kinases, good cell permeability and good PK profile. Therefore compound 6 was effective in antitumor mice model at a dose of 30 mg/kg po qd without decrease of body weight.     

Design,synthesis, quantum chemical studies and biological activity evaluation of pyrazole–benzimidazole derivatives as potent Aurora A/B kinase inhibitors

Novel pyrazole–benzimidazole derivatives have been designed and synthesized. The entire target compounds were determined against cancer cell lines U937, K562, A549, LoVo and HT29 and were screened for Aurora A/B kinase inhibitory activity in vitro. The compounds 7a, 7b, 7i, 7k and 7l demonstrated significant cancer cell lines and Aurora A/B kinase inhibitory activities. Molecular modeling studies suggested the derivatives have bound in the active site of Aurora A kinase through the formation of four hydrogen bonds. Quantum chemical studies were carried out on these compounds to understand the structural features essential for activity. The cellular activity of 7k was also tested by immunofluorescence.     

Click approach to the discovery of 1,2,3-triazolylsalicylamides as potent Aurora kinase inhibitors

A series of 1,2,3-triazolylsalicylamide derivatives has been developed from the antiproliferative agent 7 and was evaluated for their Aurora kinase inhibitory activity. The novel 1,2,3-triazolylsalicylamide scaffold could be readily assembled by Cu(I)-catalyzed azide–alkyne 1,3-dipolar cycloaddition, allowing rapid access to the structurally diverse analogues. The synthesized 1,2,3-triazolylsalicylamide derivatives revealed a significant Aurora kinase inhibitory activity. In particular, 8g inhibited Aurora A with IC₅₀ values of 0.37 μM. The critical role of phenolic –OH in the binding was confirmed by a molecular modeling study.     

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.     

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.     

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.     

Characterization of a highly selective inhibitor of the Aurora kinases

Aurora kinases play an essential role in mitosis and cell cycle regulation. In recent years Aurora kinases have proved popular cancer targets and many inhibitors have been developed. The majority of these clinical candidates are multi-targeted, rendering them inappropriate as tools for studying Aurora kinase mediated signaling. Here we report discovery of a highly selective inhibitor of Aurora kinases A, B and C, with potent cellular activity and minimal off-target activity (PLK4). The X-ray co-crystal structure of Aurora A in complex with compound 2 is reported, and provides insights into the structural determinants of ligand binding and selectivity.     

Discovery of imidazo[1,2-a]pyrazine-based Aurora kinase inhibitors

The synthesis and structure–activity relationships (SAR) of novel, potent imidazo[1,2-a]pyrazine-based Aurora kinase inhibitors are described. The X-ray crystal structure of imidazo[1,2-a]pyrazine Aurora inhibitor 1j is disclosed. Compound 10i was identified as lead compound with a promising overall profile.     

Discovery of 4-aminoquinazoline—urea derivatives as Aurora kinase inhibitors with antiproliferative activity

Two series of 20 novel 4-aminoquinazoline—urea derivatives have been designed and synthesized. The entire target compounds were investigated for their in vitro antiproliferative activity against six human cancer cell lines (K562, U937, A549, NCI-H661, HT29 and LoVo) using the MTT-based assay. Most compounds showed significant antiproliferative activities against four solid tumor cell lines, but no or poor activities against two leukemia cell lines. Furthermore, the target compounds were screened for Aurora A/B kinases inhibitory activity. Among them, 7c, 7d, 8c, and 8d are more potent against Aurora A kinase than ZM447439. Docking study of compounds 7d and ZM447439 revealed that they bound strongly to the ATP-binding sites of Aurora A and B. Thus, they may be promising lead compounds for the development of novel anti-tumor drug potentially via inhibiting Aurora kinases.     

Discovery of orally bioavailable imidazo[1,2-a]pyrazine-based Aurora kinase inhibitors

We report a series of potent imidazo[1,2-a]pyrazine-based Aurora kinase inhibitors. Optimization of the solvent accessible 8-position led to improvements in both oral bioavailability and off-target kinase inhibition. Compound 25 demonstrates anti-tumor activity in an A2780 ovarian tumor xenograft model.     

Discovery of a highly potent orally bioavailable imidazo-[1, 2-a]pyrazine Aurora inhibitor

Imidazo-[1, 2-a]pyrazine 1 is a potent inhibitor of Aurora A and B kinase in vitro and is effective in in vivo tumor models, but has poor oral bioavailbility and is unsuitable for oral dosing. We describe herein our effort to improve oral exposure in this class, resulting ultimately in the identification of a potent Aurora inhibitor 16, which exhibited good drug exposure levels across species upon oral dosing, and showed excellent in vivo efficacy in a mouse xenograft tumor model when dosed orally.     

Synthesis,biological evaluation and molecular modeling study of 2-amino-3,5-disubstituted-pyrazines as Aurora kinases inhibitors

Serine/threonine protein kinases Aurora A, B, and C play essential roles in cell mitosis and cytokinesis, and a number of Aurora kinase inhibitors have been evaluated in the clinic. Herein we report the synthesis and their antiproliferation of 3,5-disubstituted-2-aminopyrazines as kinases inhibitors. Amongst, 4-((3-amino-6- (3,5-dimethylisoxazol-4-yl)pyrazin-2-yl)oxy)-N-(3-chlorophenyl) benzamide (12Aj) exhibited the strongest antiproliferative activities against U38, HeLa, HepG2 and LoVo cells with IC₅₀ values were 11.5 ± 3.2, 1.34 ± 0.23, 7.30 ± 1.56 and 1.64 ± 0.48 μM, as well as inhibited Aurora A and B with the IC₅₀ values were 90 and 152 nM, respectively. Molecular docking studies indicated that 12Aj appeared to form stable hydrogen bonds with either Aurora A or Aurora B. Furthermore, 12Aj arrested HeLa cell cycle in G2/M phase by regulating protein levels of cyclinB1 and cdc2. In addition, the bioinformatics prediction further revealed that 12Aj possessed good drug likeness using SwissADME. These results suggested that 12Aj was worthy of future development of potent anticancer agents as pan-Aurora kinases.     

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.     

Water-soluble prodrugs of an Aurora kinase inhibitor

Compound 1 (SNS-314) is a potent and selective Aurora kinase inhibitor that is currently in clinical trials in patients with advanced solid tumors. This communication describes the synthesis of prodrug derivatives of 1 with improved aqueous solubility profiles. In particular, phosphonooxymethyl-derived prodrug 2g has significantly enhanced solubility and is converted to the biologically active parent (1) following iv as well as po administration to rodents.     

Structure-based design of imidazo[1,2-a]pyrazine derivatives as selective inhibitors of Aurora-A kinase in cells

Co-crystallisation of the imidazo[1,2-a]pyrazine derivative 15 (3-chloro-N-(4-morpholinophenyl)-6-(pyridin-3-yl)imidazo[1,2-a]pyrazin-8-amine) with Aurora-A provided an insight into the interactions of this class of compound with Aurora kinases. This led to the design and synthesis of potent Aurora-A inhibitors demonstrating up to 70-fold selectivity in cell-based Aurora kinase pharmacodynamic biomarker assays.     

Design,synthesis and biological evaluation of thienopyridinones as Chk1 inhibitors

A series of thienopyridinone derivatives was designed and synthesized as inhibitors of checkpoint kinase 1 (Chk1). Most of them exhibited moderate to good Chk1 inhibitory activities. Among them, compounds 8q, 8t, and 8w with excellent Chk1 inhibitory activities (IC₅₀ values of 4.05, 6.23, and 2.33 nM, respectively) displayed strong synergistic effects with melphalan, a DNA-damaging agent in the cell-based assay. Further kinase profiling indicated that compound 8t was highly selective against CDK2/cyclinA, Aurora A, and PKC.     

Synthesis and identification of 2,4-bisanilinopyrimidines bearing 2,2,6,6-tetramethylpiperidine-N-oxyl as potential Aurora A inhibitors

The Aurora kinases are a family of serine/threonine kinases that interact with components of the mitotic apparatus and serve as potential therapeutic targets in oncology. Herein, we reported a series of 2,4-bisanilinopyrimidines bearing 2,2,6,6-tetramethylpiperidine-N-oxyl with selective inhibition of Aurora A in either enzymatic assays or cellular phenotypic assays, and displaying more potent anti-proliferation compared with that of VX-680. The most potent compound 10a forms better interaction with Aurora A than Aurora B in molecular docking. Mechanistic studies revealed that 10a disrupt the spindle formation, block the cell cycle progression in the G2/M phase and induce apoptosis in HeLa cell. These results suggested that the produced series of compounds are potential anticancer agents for further development as selective Aurora A inhibitors.     

Synthesis and profiling of a 3-aminopyridin-2-one-based kinase targeted fragment library: Identification of 3-amino-5-(pyridin-4-yl)pyridin-2(1H)-one scaffold for monopolar spindle 1 (MPS1) and Aurora kinases inhibition

Screening a 3-aminopyridin-2-one based fragment library against a 26-kinase panel representative of the human kinome identified 3-amino-5-(1-methyl-1H-pyrazol-4-yl)pyridin-2(1H)-one (2) and 3-amino-5-(pyridin-4-yl)pyridin-2(1H)-one (3) as ligand efficient inhibitors of the mitotic kinase Monopolar Spindle 1 (MPS1) and the Aurora kinase family. These kinases are well recognised as attractive targets for therapeutic intervention for treating cancer. Elucidation of the binding mode of these fragments and their analogues has been carried out by X-ray crystallography. Structural studies have identified key interactions with a conserved lysine residue and have highlighted potential regions of MPS1 which could be targeted to improve activity and selectivity.     

Discovery and optimization of novel benzothiophene-3-carboxamides as highly potent inhibitors of Aurora kinases A and B

Aurora kinases as regulators of cell division have become promising therapeutic targets recently. Here we report novel, low molecular weight benzothiophene-3-carboxamide derivatives designed and optimized for inhibiting Aurora kinases. The most effective compound 36 inhibits Aurora kinases in vitro in the nanomolar range and diminishes HCT 116 cell viability blocking cytokinesis and inducing apoptosis. According to western blot analysis, the lead molecule inhibits Aurora kinases equipotently to VX-680 (Tozasertib) and similarly synergizes with other targeted drugs.