2,4-Diaminopyrimidine inhibitors of c-Met kinase bearing benzoxazepine anilines

Elaboration of the SAR around a series of 2,4-diaminopyrimidines led to a number of c-Met inhibitors in which kinase selectivity was modulated by substituents appended on the C4-aminobenzamide ring and the nature of the C2-aminoaryl ring. Further lead optimization of the C2-aminoaryl group led to benzoxazepine analogs whose pharmaceutical properties were modulated by the nature of the substituent on the benzoxazepine nitrogen. Tumor stasis (with partial regressions) were observed when an orally bioavailable analog was evaluated in a GTL-16 tumor xenograft mouse model. Subsequent PK/PD studies suggested that a metabolite contributed to the overall in vivo response.     

Design,synthesis and evaluation of sulfonylurea-containing 4-phenoxyquinolines as highly selective c-Met kinase inhibitors

Deregulation of receptor tyrosine kinase c-Met has been reported in human cancers and is considered as an attractive target for small molecule drug discovery. In this study, a series of 4-phenoxyquinoline derivatives bearing sulfonylurea moiety were designed, synthesized and evaluated for their c-Met kinase inhibition and cytotoxicity against tested four cell lines in vitro. The pharmacological data indicated that most of the tested compounds showed moderate to significant potency as compared with foretinib, with the most promising compound 13x (c-Met kinase IC₅₀ = 1.98 nM) demonstrated relatively good selectivity versus 10 other tyrosine kinases and remarkable cytotoxicities against HT460, MKN-45, HT-29 and MDA-MB-231 with IC₅₀ values of 0.055 µM, 0.064 µM, 0.16 µM and 0.49 µM, respectively. The preliminary structure activity relationships indicated that a sulfonylurea moiety as linker as well as mono-EGWs (such as R₁ = 4-F) on the terminal phenyl rings contributed to the antitumor activity.     

Fused bicyclic derivatives of 2,4-diaminopyrimidine as c-Met inhibitors

The HGF-c-Met signaling axis is an important paracrine mediator of epithelial-mesenchymal cell interactions involving the regulation of multiple cellular activities including cell motility, mitogenesis, morphogenesis, and angiogenesis. Dysregulation of c-Met signaling (e.g., overexpression or increased activation) is associated with the development of a wide range of tumor types; thus, inhibiting the HGF-c-Met pathway is predicted to lead to anti-tumor effects in many cancers. Elaboration of a 2-arylaminopyrimidine scaffold led to a series of potent c-Met inhibitors bearing a C4-2-amino-N-methylbenzamide group. Specifically, a series of C2-benzazepinone analogs demonstrated potent inhibition of c-Met in enzymatic and cellular assays. Kinase selectivity could be tuned by varying the nature of the alkyl group on the benzazepinone nitrogen.     

Discovery and optimization of novel 4-phenoxy-6,7-disubstituted quinolines possessing semicarbazones as c-Met kinase inhibitors

A novel series of N¹-(3-fluoro-4-(6,7-disubstituted-quinolin-4-yloxy)phenyl)-N⁴-arylidenesemicarbazide derivatives were synthesized and evaluated for their c-Met kinase inhibition and cytotoxicity against A549, HT-29, MKN-45 and MDA-MB-231 cancer cell lines in vitro. Several potent compounds were further evaluated against three other cancer cell lines (U87MG, NCI-H460 and SMMC7721). Most of compounds tested exhibited moderate to excellent activity. The studies of SARs identified the most promising compound 28 (c-Met IC₅₀ = 1.4 nM) as a c-Met kinase inhibitor. In this study, a promising compound 28 was identified, which displayed 2.1-, 3.3-, 48.4- and 3.6-fold increase against A549, HT-29, U87MG and NCI-H460 cell lines, respectively, compared with that of Foretinib.     

Molecular imaging of c-Met tyrosine kinase activity

The receptor tyrosine kinase c-Met and its ligand, hepatocyte growth factor/scatter factor (HGF/SF), modulate signaling cascades implicated in cellular proliferation, survival, migration, invasion, and angiogenesis. Therefore, dysregulation of HGF/c-Met signaling can compromise the cellular capacity to moderate these activities and can lead to tumorigenesis, metastasis, and therapeutic resistance in various human malignancies. To facilitate studies investigating HGF/c-Met receptor coupling or c-Met signaling events in real time and in living cells and animals, here we describe a genetically engineered reporter where bioluminescence can be used as a surrogate for c-Met tyrosine kinase activity. c-Met kinase activity in cultured cells and tumor xenografts was monitored quantitatively and dynamically in response to the activation or inhibition of the HGF/c-Met signaling pathway. Treatment of tumor-bearing animals with a c-Met inhibitor and the HGF neutralizing antibody stimulated the reporter’s bioluminescence activity in a dose-dependent manner and led to a regression of U-87 MG tumor xenografts. Results obtained from these studies provide unique insights into the pharmacokinetics and pharmacodynamics of agents that modulate c-Met activity and validate c-Met as a target for human glioblastoma therapy.     

The discovery of benzanilides as c-Met receptor tyrosine kinase inhibitors by a directed screening approach

A directed screen of a relatively small number of compounds, selected for kinase ATP pocket binding potential, yielded a novel series of hit compounds (1). Hit explosion on two binding residues identified compounds 27 and 43 as the best leads for an optimization program having reduced secondary metabolism, as measured by in vitro rat hepatocytes incubation, leading to oral bio-availability. Structure-activity relationships and molecular modeling have suggested a binding mode for the most potent inhibitor 12.     

Design,synthesis and evaluation of highly selective pyridone-based class II MET inhibitors

The high incidence of MET oncogene activation in human malignancies has prompted researchers to develop MET inhibitors. As part of our efforts to developing effective and safe therapeutic agents against MET-dependent tumors, a pyridone-based class II MET inhibitor, namely, 1-(4-((2-amino-3-iodopyridin-4-yl)-oxy)-3-fluorophenyl)-N-(4-fluorobenzyl)-4-methoxy-6-oxo-1,6-dihydropyridine-3-carboxamide (3s), was identified. Knowledge of the binding mode of class II MET inhibitors led to the design of new inhibitors that utilize 2-pyridone to conformationally restrain key pharmacophoric groups within the molecule. Integrated molecular docking and SAR studies resulted in the discovery of a novel class of pyridone MET inhibitors with high potency (IC₅₀ of 0.005 μM) and efficient selectivity (>5000 fold) to VEGFR-2, c-Kit and RET kinases.     

Divergent synthesis of kinase inhibitor derivatives,leading to discovery of selective Gck inhibitors

We accomplished divergent synthesis of potent kinase inhibitor BAY 61-3606 (1) and 27 derivatives via conjugation of imidazo[1,2-c]pyrimidine and indole ring compounds with aromatic (including pyridine) derivatives by means of palladium-catalyzed cross-coupling reaction. Spleen tyrosine kinase (Syk) and germinal center kinase (Gck, MAP4K2) inhibition assays showed that some of the synthesized compounds were selective Gck inhibitors.     

Discovery and synthesis of novel 4-aminopyrrolopyrimidine Tie-2 kinase inhibitors for the treatment of solid tumors

The synthesis and biological evaluation of novel Tie-2 kinase inhibitors are presented. Based on the pyrrolopyrimidine chemotype, several new series are described, including the benzimidazole series by linking a benzimidazole to the C5-position of the 4-amino-pyrrolopyrimidine core and the ketophenyl series synthesized by incorporating a ketophenyl group to the C5-position. Medicinal chemistry efforts led to potent Tie-2 inhibitors. Compound 15, a ketophenyl pyrrolopyrimidine urea analog with improved physicochemical properties, demonstrated favorable in vitro attributes as well as dose responsive and robust oral tumor growth inhibition in animal models.     

5-Keto-3-cyano-2,4-diaminothiophenes as selective maternal embryonic leucine zipper kinase inhibitors

Maternal embryonic leucine zipper kinase (MELK) is involved in several key cellular processes and displays increased levels of expression in numerous cancer classes (colon, breast, brain, ovary, prostate and lung). Although no selective MELK inhibitors have yet been approved, increasing evidence suggest that inhibition of MELK would constitute a promising approach for cancer therapy. A weak high-throughput screening hit (17, IC₅₀?≈?5?μM) with lead-like properties was optimized for MELK inhibition. The early identification of a plausible binding mode by molecular modeling offered guidance in the choice of modifications towards compound 52 which displayed a 98?nM IC₅₀. A good selectivity profile was achieved for a representative member of the series (29) in a 486 protein kinase panel. Future elaboration of 52 has the potential to deliver compounds for further development with chemotherapeutic aims.     

Discovery of a novel and potent series of thieno[3,2-b]pyridine-based inhibitors of c-Met and VEGFR2 tyrosine kinases

A series of thieno[3,2-b]pyridine-based inhibitors of c-Met and VEGFR2 tyrosine kinases is described. The compounds demonstrated potency with IC₅₀ values in the low nanomolar range in vitro while the lead compound also showed in vivo activity against various human tumor xenograft models in mice. Further exploration of this class of compounds is underway.     

Design,synthesis and biological evaluation of novel 6,7-disubstituted-4-phenoxyquinoline derivatives bearing 4-oxo-3,4-dihydrophthalazine-1-carboxamide moieties as c-Met kinase inhibitors

A series of 6,7-disubstituted-4-phenoxyquinoline derivatives bearing 4-oxo-3,4-dihydrophthalazine-1-carboxamide moieties were designed, synthesized and evaluated for their c-Met kinase inhibition and cytotoxicity against H460, MKN-45, HT-29 and MDA-MB-231 cancer cell lines in vitro. Most compounds displayed good to excellent potency against four tested cancer cell lines as compared with foretinib. The SAR analyses indicated that compounds with halogen groups, especially fluoro groups at 4-position on the phenyl ring (moiety B) were more effective than those with nitro groups or methoxy groups. In this study, a promising compound 33 (c-Met IC₅₀ = 1.63 nM) was identified, which showed the most potent antitumor activities with IC₅₀ values of 0.055 μM, 0.071 μM, 0.13 μM, and 0.43 μM against H460, MKN-45, HT-29 and MDA-MB-231 cell lines, respectively.     

3,5-diarylazoles as novel and selective inhibitors of protein kinase D

The synthesis and preliminary studies of the SAR of novel 3,5-diarylazole inhibitors of Protein Kinase D (PKD) are reported. Notably, optimized compounds in this class have been found to be active in cellular assays of phosphorylation-dependant HDAC5 nuclear export, orally bioavailable, and highly selective versus a panel of additional putative histone deacetylase (HDAC) kinases. Therefore these compounds could provide attractive tools for the further study of PKD / HDAC5 signaling.     

Design,synthesis, and biological evaluation of 4-phenoxyquinoline derivatives as potent c-Met kinase inhibitor

A series of novel 4-phenoxyquinoline derivatives containing 3-oxo-3,4-dihydro-quinoxaline moiety were synthesized and evaluated for their antiproliferative activity against five human cancer cell lines (A549, H460, HT-29, MKN-45 and U87MG) in vitro. Most of the tested compounds exhibited more potent inhibitory activities than the positive control foretinib. Compound 1b, 1s and 1t were further examined for their inhibitory activity against c-Met kinase. The most promising compound 1s (with c-Met IC₅₀ value of 1.42 nM) showed remarkable cytotoxicity against A549, H460, HT-29, MKN45 and U87MG cell lines with IC₅₀ values of 0.39 μM, 0.18 μM, 0.38 μM, 0.81 μM, respectively. Their preliminary structure-activity relationships (SARs) study indicated that the replacement of the aromatic ring with the cyclohexane improved their antiproliferative activity.     

Discovery and optimization of potent and selective triazolopyridazine series of c-Met inhibitors

Deregulation of the receptor tyrosine kinase c-Met has been implicated in several human cancers and is an attractive target for small molecule drug discovery. We previously showed that O-linked triazolopyridazines can be potent inhibitors of c-Met. Herein, we report the discovery of a related series of N-linked triazolopyridazines which demonstrate nanomolar inhibition of c-Met kinase activity and display improved pharmacodynamic profiles. Specifically, the potent time-dependent inhibition of cytochrome P450 associated with the O-linked triazolopyridazines has been eliminated within this novel series of inhibitors. N-linked triazolopyridazine 24 exhibited favorable pharmacokinetics and displayed potent inhibition of HGF-mediated c-Met phosphorylation in a mouse liver PD model. Once-daily oral administration of 24 for 22 days showed significant tumor growth inhibition in an NIH-3T3/TPR-Met xenograft mouse efficacy model.     

Discovery of 6-benzyloxyquinolines as c-Met selective kinase inhibitors

A novel quinoline derivative that selectively inhibits c-Met kinase was identified. The molecular design is based on a result of the analysis of a PF-2341066 (1)/c-Met cocrystal structure (PDB code: 2wgj). The kinase selectivity of the derivatives is discussed from the view point of the sequence homology of the kinases, the key interactions found in X-ray cocrystal structures, and the structure–activity relationship (SAR) obtained in this work.     

Synthesis and bioevaluation study of novel N-methylpicolinamide and thienopyrimidine derivatives as selectivity c-Met kinase inhibitors

Four series of N-methylpicolinamide moiety and thienopyrimidine moiety bearing pyridazinone were designed and synthesized and evaluated for the IC₅₀ values against three cancer cell lines (A549, HepG2 and MCF-7) and some selected compounds were further evaluated for the activity against c-Met, Flt-3, VEGFR-2, c-Kit and EGFR kinases. Three compounds (35, 39 and 43) showed more active than positive control Foretinib against A549, HepG2 and MCF-7 cell lines. The most promising compound 43 showed superior activity against A549, HepG2 and MCF-7, with the IC₅₀ values of 0.58?±?0.15?µM, 0.47?±?0.06?µM and 0.74?±?0.12?µM, which were 3.73–5.39-fold more activity than Foretinib, respectively. The experiments of enzyme-based showed that 43 restrain the c-Met selectively, with the IC₅₀ values of 16?nM, which showed equal activity to Foretinib (14?nM) and better than the compound 5 (90?nM). Moreover, AO and Annexin V/PI staining and docking studies were carried out.     

Discovery of aminopyridines substituted with benzoxazole as orally active c-Met kinase inhibitors

We report the synthesis and biological evaluation of aminopyridines substituted with benzoxazole. The SAR of the aminopyridines was explored to improve the inhibitory activity against c-Met and to decrease hERG affinity. These studies led to the discovery of amide 24 which showed good c-Met inhibitory potency, low affinity to hERG and favorable pharmacokinetic properties in rats.     

Synthesis and structure-activity relationship of aminopyridines with substituted benzoxazoles as c-Met kinase inhibitors

A series of hydroxybenzoxazole derivatives was synthesized, and their c-Met kinase inhibitory activity was evaluated. Described herein is a potent c-Met inhibitor by structural modification of the parent benzoxazole scaffold, with particular focus on the hydroxyl substituent of the benzoxazole moiety.     

Highly selective c-Jun N-terminal kinase (JNK) 2 and 3 inhibitors with in vitro CNS-like pharmacokinetic properties prevent neurodegeneration

In this Letter, we describe the discovery of selective JNK2 and JNK3 inhibitors, such as 10, that routinely exhibit >10-fold selectivity over JNK1 and >1000-fold selectivity over related MAPKs, p38α and ERK2. Substitution of the naphthalene ring affords an isoform selective JNK3 inhibitor, 30, with approximately 10-fold selectivity over both JNK1 and JNK2. A naphthalene ring penetrates deep into the selectivity pocket accounting for the differentiation amongst the kinases. Interestingly, the gatekeeper Met146 sulfide interacts with the naphthalene ring in a sulfur-π stacking interaction. Compound 38 ameliorates neurotoxicity induced by amyloid-β in human cortical neurons. Lastly, we demonstrate how to install propitious in vitro CNS-like properties into these selective inhibitors.