Discovery of N-substituted-3-phenyl-1,6-naphthyridinone derivatives bearing quinoline moiety as selective type II c-Met kinase inhibitors against VEGFR-2

New N-substituted-3-phenyl-1,6-naphthyridinone derivatives are designed and synthesized, based on structural modification of our previously reported compound 3. Extensive enzyme-based SAR studies and PK evaluation led to the discovery of compound 4r, with comparable c-Met potency to that of Cabozantinib and high VEGFR-2 selectivity, while Cabozantinib displayed no VEGFR-2 selectivity. More importantly, at oral doses of 45 mg/kg (Q.D.), compound 4r exhibits significant tumor growth inhibition (93%) in a U-87MG human gliobastoma xenograft model. The promising selectivity against VEGFR-2 and excellent tumor growth inhibition of compound 4r suggest that it could be used as a new lead molecule for further discovery of selective type II c-Met inhibitors.     

Synthesis and biological evaluation of novel (E)-N'-benzylidene hydrazides as novel c-Met inhibitors through fragment based virtual screening

Abstract

C-Met plays a crucial role in the development and progression of neoplastic disease. Type II c-Met inhibitors recognise the inactive DFG-out conformation of the kinase, result in better anti-tumour effects due to synergistic effect against the other kinases. According to our previous works, an (E)-N'-benzylidene group was selected as the initial fragment. Two series of (E)-N'-benzylidene hydrazides were designed by fragment growth method. The inhibitory activities were in vitro investigated against c-Met and VEGFR-2. Compound 10b exhibited the most potent inhibitory activity against the c-Met inhibitor (IC₅₀ = 0.37?nM). Compound 11b exhibited multi-target c-Met kinase inhibitory activity as a potential type II c-Met inhibitor (IC₅₀ = 3.41?nM against c-Met; 25.34?nM against VEGFR-2). The two compounds also demonstrate the feasibility of fragment-based virtual screening method for drug discovery.     

Synthesis and biological evaluation of 2-amino-5-aryl-3-benzylthiopyridine scaffold based potent c-Met inhibitors

A series of 2-amino-N-benzylpyridine-3-carboxnamides, 2-amino-N-benzylpyridine-3-sulfonamides and 2-amino-3-benzylthiopyridines against c-Met were designed by means of bioisosteric replacement and docking analysis. Optimization of the 2-amino-3-benzylthiopyridine scaffold led to the identification of compound (R)-10b displaying c-Met inhibition with an IC₅₀ up to 7.7 nM. In the cytotoxic evaluation, compound (R)-10b effectively inhibited the proliferation of c-Met addictive human cancer cell lines (IC₅₀ from 0.19 to 0.71 μM) and c-Met activation-mediated cell metastasis. At a dose of 100 mg/Kg, (R)-10b evidently inhibited tumor growth (45%) in NIH-3T3/TPR-Met xenograft model. Of note, (R)-10b could overcome c-Met-activation mediated gefitinib-resistance, which indicated its potential use for drug combination. Taken together, 2-amino-3-benzylthiopyridine scaffold was first disclosed and exhibited promising pharmacological profiles against c-Met, which left room for further exploration.     

CD44v6 coordinates tumor matrix-triggered motility and apoptosis resistance

Tumor progression requires a crosstalk with the tumor surrounding, where the tumor matrix plays an essential role. We recently reported that only the matrix delivered by a CD44v6-competent (ASML(wt)), but not that of a CD44v6-deficient (ASML-CD44v(kd)) rat pancreatic adenocarcinoma line supports metastasis formation. We here describe that this matrix provides an important feedback toward the tumor cell and that CD44v6 accounts for orchestrating signals received from the matrix. ASML(wt) cells contain more hyaluronan synthase-3 and secrete higher amounts of >50 kDa HA than ASML-CD44v(kd) cells, which secrete more hyaluronidase. Only the ASML(wt)-matrix supports migration and apoptosis resistance, which both can be initiated via CD44v6, c-Met, and α6β4 ligand binding and proceed via FAK, PI3K/Akt, and MAPK activation, respectively. However, c-Met- and α6β4-initiated signaling are strongly augmented by the association with CD44v6 as only very weak effects are observed in CD44v6-deficient cells. The same CD44v6-dependent convergence of motility- and apoptosis resistance-related signals also accounts for human tumor lines. Thus, CD44v6 promotes motility and apoptosis resistance via its involvement in assembling a matrix that, in turn, triggers activation of signaling cascades, which proceeds, independent of the initiating receptor-ligand interaction, in a concerted action via CD44v6.     

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.     

Identification and synthesis of N'-(2-oxoindolin-3-ylidene)hydrazide derivatives against c-Met kinase

A series of N′-(2-oxoindolin-3-ylidene)hydrazide derivatives were identified as moderately potent inhibitors against c-Met kinase by pharmacophore-based virtual screening and chemical synthesis methods. The structure-activity relationship (SAR) at various positions of the scaffold was investigated and its binding mode with c-Met kinase was analyzed by molecular modeling studies. In this study, two potent compounds D2 and D25, with IC₅₀ value at 1.3 μM and 2.2 μM against c-Met kinase respectively, were identified. Finally, based on the clues extracted from this study, future development for the optimization of this scaffold was discussed.     

Mucin 20 modulates proteasome capacity through c-Met signalling to increase carfilzomib sensitivity in mantle cell lymphoma

Mantle cell lymphoma (MCL) is a haematologic malignancy. The proteasome inhibitor (PI) bortezomib has been approved to treat MCL, but resistance has emerged through mechanisms that remain unclear. This study aimed to explore the mechanism of PI resistance in MCL and identify new targets for this patient subgroup. Carfilzomib-resistant (CR) MCL cell lines and primary samples were used for both in vitro and in vivo experiments to identify gene expression and explore their related signalling pathways. We first identified mucin 20 (MUC20) suppression in carfilzomib-resistant MCL models. MUC20 overexpression sensitized cells to carfilzomib in vitro and in vivo. MUC20 expression was inversely related to activation of c-Met and the downstream p44/42 MAPK pathway. c-Met activation with hepatocyte growth factor (HGF) induced PI resistance, while c-Met inhibition restored PI sensitivity. Carfilzomib resistance and depressed MUC20 expression were associated with enhanced proteasome activity and higher expression of proteassemblin (POMP), a chaperone for catalytically active proteasome assembly. c-Met and POMP were associated through binding and induction of MAPK-regulated ELK1 to the POMP promoter. Our data reveal that c-Met signalling activation enhanced proteasome capacity as a mechanism of PI resistance, and MUC20 expression may be a useful biomarker for PI therapy.     

Design,synthesis and molecular modeling studies of new series of antitumor 1,2,4-triazines with potential c-Met kinase inhibitory activity

The receptor tyrosine kinase c-Met is an attractive target for therapeutic treatment of cancers nowadays. Herein we describe the design and synthesis of a novel series of 1,2,4-triazine derivatives based on our lead NCI 748494/1, possessing different N-linkers to aromatic and heterocyclic rings. In addition, a molecular hybrid series combining the 1,2,4-triazine scaffold to the well-known anticancer drug 6-mercaptopurine (6-MP) was synthesized in order to explore its “double-drug” antitumor effect. The synthesized compounds were evaluated for their in vitro antitumor activity against three c-Met addicted cancer cell lines (A549, HT-29 and MKN-45). Most compounds showed moderate to excellent antitumor activity. Compound 3d showed potent inhibitory activity more than reference Foretinib, BMS-777607 and NCI 748494/1 with IC₅₀ values in the range 0.01–0.31 µM against the cancer cell lines. The calculated IC₅₀ of 3d against c-Met kinase was found to be 2.71 µM, which is more potent than NCI 748494/1 (IC₅₀ = 31.70 µM). Docking studies were performed to identify the binding mode of 3d with c-Met kinase domain in comparison to moderate and weak derivatives. The present study clearly demonstrates that 1,2,4-triazine ring exhibits promising antitumor activity and the double-drug optimization strategy led to identifying 3d as a potent c-Met kinase inhibitor suitable for further development.     

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.     

Exogenously administered HGF activator augments liver regeneration through the production of biologically active HGF.

Hepatocyte growth factor (HGF) plays a crucial role in the recovery of injured liver. Liver functions are mostly impaired in patients with liver diseases including cirrhosis. However, a significant amount of inactive HGF precursor (proHGF) is reported in the plasma of these patients. proHGF is proteolytically converted to an active form (mature HGF) by HGF-activator. Thus conversion of proHGF into mature HGF presumably contributes to the recovery of liver functions. In this study, rats with a partial hepatectomy were used, as proHGF is accumulated in the remnant liver. Recombinant human HGF-activator was administered via the portal vein to investigate the effect on molecular forms of HGF and its biological signaling. rhHGF-activator promptly converted proHGF into mature HGF, reaching maximal levels at 5-10 min after the injection, while the decreased proHGF was quickly recovered to the initial levels in the liver. The HGF receptor/c-Met was found to be autophosphorylated in the liver treated with rhHGF-activator. Further, the proliferating cell nuclear antigen labeling index and the liver regeneration rate were significantly higher in rhHGF-activator group than in control animals. These results indicate that exogenously administered HGF-activator produces a biologically active HGF from its precursor form and increases the potential for liver regeneration in vivo.