Discovery of novel 2-substituted-4-(2-fluorophenoxy) pyridine derivatives possessing pyrazolone and triazole moieties as dual c-Met/VEGFR-2 receptor tyrosine kinase inhibitors

In our efforts to develop novel dual c-Met/VEGFR-2 inhibitors as potential anticancer agents, a series of 2-substituted-4-(2-fluorophenoxy) pyridine derivatives bearing pyrazolone scaffold were designed and synthesized. The cell proliferation assay in vitro demonstrated that most target compounds had inhibition potency on both c-Met and VEGFR-2, especially compound 9h, 12b and 12d. Based on the further enzyme assay in vitro, compound 12d was considered as the most promising one, the IC₅₀ values of which were 0.11 μM and 0.19 μM for c-Met and VEGFR-2, respectively. Further molecular docking studies suggested a common mode of interaction at the ATP-binding site of c-Met and VEGFR-2, indicating that 12d was a potential compound for cancer therapy deserving further study.     

Synthesis and anti-tumor activity of [1,4] dioxino [2,3-f] quinazoline derivatives as dual inhibitors of c-Met and VEGFR-2

Both c-Met and VEGFR-2 were important targets for cancer therapies. In order to develop reversible and non-covalent c-Met and VEGFR-2 dual inhibitors, a series of [1,4]dioxino[2,3-f]quinazoline derivatives were designed and synthesized. The enzyme assay demonstrated that most target compounds had inhibition potency on both c-Met and VEGFR-2 with IC₅₀ values in nanomolar range especially compounds 7m and 7k. Based on further cell proliferation assay in vitro, compound 7k showed significantly anti-tumor activity in vivo on a hepatocellular carcinoma (MHCC97H cells) xenograft mouse model. We docked the compound 7m with c-Met and VEGFR-2 kinases, and interpreted the SAR of these analogues. All results indicated that the target compounds were dual inhibitors of c-Met and VEGFR-2 kinases that held promising potential in cancer therapy.     

Design,synthesis and biological evaluation of 4-aminopyrimidine-5-cabaldehyde oximes as dual inhibitors of c-Met and VEGFR-2

The synergistically collaboration of c-Met/HGF and VEGFR-2/VEGF leads to development of tumor angiogenesis and progression of various human cancers. Therefore, inhibiting both HGF/c-Met and VEGF/VEGFR signaling may provide a novel and effective therapeutic approach for treating patients with abroad spectrum of tumors. Toward this goal, we designed and synthesized a series of derivatives bearing 4-aminopyrimidine-5-cabaldehyde oxime scaffold as potent dual inhibitors of c-Met and VEGFR-2. The cell proliferation assay in vitro demonstrated most target compounds have inhibition potency both on c-Met and VEGFR-2 with IC₅₀ values in nanomolar range, especially compound 14i, 18a and 18b. Based on the further enzyme assay in vitro, compound 18a was considered as the most potent one, the IC₅₀s of which were 210 nM and 170 nM for c-Met and VEGFR-2, respectively. Following that, we docked the compound 10 and 18a with the proteins c-Met and VEGFR-2, and interpreted the SAR of these analogs. All the results indicate that 18a is a dual inhibitors of c-Met and VEGFR-2 that holds promising potential.     

Novel 5-(benzyloxy)pyridin-2(1H)-one derivatives as potent c-Met inhibitors

A series of novel 5-(benzyloxy)pyridin-2(1H)-ones were designed, synthesized and biologically evaluated for c-Met inhibition. Various amides and benzoimidazoles at C-3 position were investigated. A potent compound 12b with a c-Met IC₅₀ of 12 nM was identified. This compound exhibited potent inhibition of EBC-1 cell associated with c-Met constitutive activation and showed high selectivity for c-Met than other tested 11 kinases. The binding model 12b with c-Met was disclosed by docking analysis.     

Discovery of quinazolin-4-amines bearing benzimidazole fragments as dual inhibitors of c-Met and VEGFR-2

Both c-Met and VEGFR-2 are important targets for the treatment of cancers. In this study, a series of N-(2-phenyl-1H-benzo[d]imidazol-5-yl)quinazolin-4-amine derivatives were designed and identified as dual c-Met and VEGFR-2 inhibitors. Among these compounds bearing quinazoline and benzimidazole fragments, compound 7j exhibited the most potent inhibitory activity against c-Met and VEGFR-2 with IC₅₀ of 0.05 μM and 0.02 μM, respectively. It also showed the highest anticancer activity against the tested cancer cell lines with IC₅₀ of 1.5 μM against MCF-7 and 8.7 μM against Hep-G2. Docking simulation supported the initial pharmacophoric hypothesis and suggested a common mode of interaction at the ATP-binding site of c-Met and VEGFR-2, which demonstrates that compound 7j is a potential agent for cancer therapy deserving further researching.     

Synthesis and biological evaluation of new [1,2,4]triazolo[4,3-a]pyridine derivatives as potential c-Met inhibitors

A series of [1,2,4]triazolo[4,3-a]pyrazine derivatives (4a–4i) were designed, synthesized and evaluated for their c-Met kinase inhibition and antitumor activity against SNU5 gastric cell line in vitro. Among these compounds, 4d was found to show the highest activity against c-Met and high selectivity against the tumor cells which are believed to be dependent on the c-Met oncogene amplification, because 4d selectively inhibited c-Met while had no effect on other 59 kinases. In vivo efficacy study on human gastric (MKN-45) and human non-small cell lung (NCI-H1993) tumor xenograft in nude mouse demonstrated that 4d·CH₃SO₃H had a better inhibiting activity than SGX-523 in a dose-dependent manner. When tested in mice, compound 4d·CH₃SO₃H was found to have biological half-lives and plasma exposure values higher than those of JNJ-38877605, and its long-term toxicity and acute toxicity turned out to be acceptable, all of which indicates that 4d·CH₃SO₃H is a desirable drug candidate.     

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.     

Discovery of novel pyrrolo[2,3-b]pyridine derivatives bearing 4-oxoquinoline moiety as potential antitumor inhibitor

A series of pyrrolo[2,3-b]pyridine derivatives bearing 4-oxoquinoline moiety were designed, synthesized and evaluated for the anti-proliferative on three cancer cell lines (A549, HepG2 and MCF-7) in vitro. Most of the compounds showed moderate to high potency. Some excellent compounds were tested for the inhibitory activity of c-Met kinase. Compound 34 (c-Met IC₅₀ = 17 nM) was investigated the selectivity against Flt-3, c-Kit, VEGFR-2, ALK, PDGFR-β and RON. Structure-activity relationship studies indicated that hydrogen, fluorine atom, and mono-electron-withdrawing groups (mono-EWGs, such as R² = F) on R, R¹ and R², respectively, were beneficial for the anti-proliferative activities of the target compounds. Besides, we have took further study on the combined mode between compound 34 and c-Met kinase through molecular docking.     

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.     

Imidazo[1,5-a]pyrazines: orally efficacious inhibitors of mTORC1 and mTORC2

The discovery and optimization of a series of imidazo[1,5-a]pyrazine inhibitors of mTOR is described. HTS hits were optimized for potency, selectivity and metabolic stability to provide the orally bioavailable proof of concept compound 4c that demonstrated target inhibition in vivo and concomitant inhibition of tumor growth in an MDA-MB-231 xenograft model.     

Design,synthesis and biological evaluation of novel 4-phenoxy-6,7-disubstituted quinolines possessing (thio)semicarbazones as c-Met kinase inhibitors

In continuing our efforts to identify small molecules able to inhibit c-Met kinase, three series of novel 6,7-disubstituted-4-phenoxyquinoline derivatives (23a–w, 26a–d and 30a–d) bearing (thio)semicarbazone scaffold were designed, synthesized and evaluated for their cytotoxicity. The biological data revealed that most compounds exhibited moderate-to-excellent activity against HT-29, MKN-45, A549 cancer cell lines and relative poor potency toward MDA-MB-231 cell as well as hardly any cytotoxicity in normal PBL cell. Eleven compounds were further examined for their inhibitory activity against c-Met kinase and three compounds (23h, 23n and 26a) demonstrated good inhibitory activity. This work resulted in the discovery of a potent c-Met inhibitor 23n, bearing 2-hydroxy-3-allylphenyl group at R² moiety, as a valuable lead molecule, which possessed remarkable cytotoxicity and high selectivity against A549 and HT-29 cell lines with IC₅₀ values of 11 nM and 27 nM. Besides, it displayed excellent c-Met kinase inhibition on a single-digital nanomolar level (IC₅₀ = 1.54 nM). Meanwhile, the results from preliminarily in vivo study reflected that compound 23n showed promising overall PK profiles, consistent with the efficacy in both MKN-45 and HT-29 tumor xenograft mice model. These results clearly indicated that compound 23n is a potent and highly selective c-Met inhibitor and its favorable in vitro and in vivo profiles warrant further investigation.     

Synthesis and biological evaluation of sorafenib- and regorafenib-like sEH inhibitors

To reduce the pro-angiogenic effects of sEH inhibition, a structure–activity relationship (SAR) study was performed by incorporating structural features of the anti-angiogenic multi-kinase inhibitor sorafenib into soluble epoxide hydrolase (sEH) inhibitors. The structural modifications of this series of molecules enabled the altering of selectivity towards the pro-angiogenic kinases C-RAF and vascular endothelial growth factor receptor-2 (VEGFR-2), while retaining their sEH inhibition. As a result, sEH inhibitors with greater potency against C-RAF and VEGFR-2 were obtained. Compound 4 (t-CUPM) possesses inhibition potency higher than sorafenib towards sEH but similar against C-RAF and VEGFR-2. Compound 7 (t-CUCB) selectively inhibits sEH, while inhibiting HUVEC cell proliferation, a potential anti-angiogenic property, without liver cancer cell cytotoxicity. The data presented suggest a potential rational approach to control the angiogenic responses stemming from sEH inhibition.     

Quinoxalinone (Part II). Discovery of (Z)-3-(2-(pyridin-4-yl)vinyl)quinoxalinone derivates as potent VEGFR-2 kinase inhibitors

Inhibition of VEGFR-2 kinase has been highlighted as one of the well-defined strategies to suppress tumor growth via blockade of angiogenesis. Guided by the principles of bioisosteric replacement and pharmacophoric fragment migration, a series of novel quinoxalinone derivates were designed, synthesized and evaluated for their VEGFR-2 inhibitory potencies. Among them, compounds 7c, 8b, 8c, 8e and 10b displayed antiangiogenic abilities via the in vitro tube formation assay (cellular level) and ex vivo rat aortic ring assay (tissue level) at a low concentration (0.1 μM). By means of in vivo zebrafish embryo model, two (Z)-3-(2-(pyridin-4-yl)vinyl)quinoxalinone derivates 8c and 8e showed significant antiangiogenesis effects, suggesting they have potentials to be developed into antiangiogenesis agents via further structural optimization. Moreover, these two compounds also demonstrated potent inhibition toward VEGFR-2 and B-raf kinases in a low concentration (1 μM). A possible interpretation of our evaluation result has been presented by a molecular docking study by docking representative compound 8c with VEGFR-2.     

Highly potent and selective 3-N-methylquinazoline-4(3H)-one based inhibitors of B-RafV600E kinase

Herein we describe the design of a novel series of ATP competitive B-Raf inhibitors via structure-based methods. These 3-N-methylquinazoline-4(3H)-one based inhibitors exhibit both excellent cellular potency and striking B-Raf selectivity. Optimization led to the identification of compound 16, a potent, selective and orally available agent with excellent pharmacokinetic properties and robust tumor growth inhibition in xenograft studies. Our work also demonstrates that by replacing an aryl amide with an aryl sulfonamide, a multikinase inhibitor such as AZ-628, can be converted to a selective B-Raf inhibitor, a finding that should have broad application in kinase drug discovery.     

Discovery of novel 2-substituted-4-phenoxypyridine derivatives as potential antitumor agents

A series of 2-substituted-4-phenoxypyridine derivatives were designed, synthesized, and evaluated for their antiproliferative activity against 4 cancer cell lines (A549, HT-29, H460, and U87MG) in vitro. Most compounds showed moderate to excellent potency. Nine tyrosine kinases (c-Met, Flt-3, ALK, VEGFR-2, VEGFR-3, PDGFR-α, PDGFR-β, c-Kit, and EGFR) were used to evaluate the inhibitory activities with the most promising analogue 39, which showed the Flt-3/c-Met IC₅₀ values of 2.18/2.61?nM. Structure-activity relationship studies indicated that n-Pr served as R¹ group showed a higher preference, and stronger mono-EWGs on the phenyl ring (such as R²?=?4-F) was benefited to the potency.     

Design,synthesis and molecular modeling study of certain VEGFR-2 inhibitors based on thienopyrimidne scaffold as cancer targeting agents

Different series of novel thieno [2,3-d]pyrimidine derivative (9a-d,10a-f,l,m and 15a-m) were designed, synthesized and evaluated for their ability to in vitro inhibit VEGFR-2 enzyme. Also, the cytotoxicity of the final compounds was tested against a panel of 60 different human cancer cell lines by NCI. The VEGFR-2 enzyme inhibitory results revealed that compounds 10d, 15d and 15 g are among the most active inhibitors with IC₅₀ values of 2.5, 5.48 and 2.27 µM respectively, while compound 10a remarkably showed the highest cell growth inhibition with mean growth inhibition (GI) percent of 31.57%. It exhibited broad spectrum anti-proliferative activity against several NCI cell lines specifically on human breast cancer (T7-47D) and renal cancer (A498) cell lines of 85.5% and 77.65% inhibition respectively. To investigate the mechanistic aspects underlying the activity, further biological studies like flow cytometry cell cycle together with caspase-3 colorimetric assays were carried on compound 10a. Flow cytometric analysis on both MCV-7 and PC-3 cancer cells revealed that it induced cell-cycle arrest in the G0-G1phase and reinforced apoptosis via activation of caspase-3. Furthermore, molecular modeling studies have been carried out to gain further understanding of the binding mode in the active site of VEGFR-2 enzyme and predict pharmacokinetic properties of all the synthesized inhibitors.     

Discovery of 4-ethoxy-7H-pyrrolo[2,3-d]pyrimidin-2-amines as potent,selective and orally bioavailable LRRK2 inhibitors

Inhibition of LRRK2 kinase activity with small molecules has emerged as a potential novel therapeutic treatment for Parkinson’s disease. Herein we disclose the discovery of a 4-ethoxy-7H-pyrrolo[2,3-d]pyrimidin-2-amine series as potent LRRK2 inhibitors identified through a kinase-focused set screening. Optimization of the physicochemical properties and kinase selectivity led to the discovery of compound 7, which exhibited potent in vitro inhibition of LRRK2 kinase activity, good physicochemical properties and kinase selectivity across the kinome. Moreover, compound 7 was able to penetrate into the CNS, and in vivo pharmacology studies revealed significant inhibition of Ser935 phosphorylation in the brain of both rats (30 and 100?mg/kg) and mice (45?mg/kg) following oral administration.     

Design and synthesis of novel pyridazinoquinazoline derivatives as potent VEGFR-2 inhibitors: In vitro and in vivo study

Worldwide, Hepatocellular Carcinoma (HCC) endures to be a prominent cause of cancer death. Treatment of HCC follows multiple therapies which are not entirely applicable for treatment of all patients. HCC usually arises contextual to chronic liver diseases and is often discovered at later stages which makes treatment options more complex. The present study aimed at design, synthesis & evaluation of new pyridazinoquinazoline derivatives as potential nontoxic anti-hepatocellular carcinoma (HCC) agents, through inhibition of Vascular endothelial growth factor -2 (VEGFR-2). Novel Pyridazino[3, 4, 5-de]quinazoline derivatives (2-6) were designed & synthesized. Their structures were confirmed via spectral and microanalytical data. They were tested for their in vitro VEGFR-2 inhibition & anticancer activity against human liver cancer cell line (HEPG-2). Molecular docking was investigated into VEGFR-2 site. In vivo studies of VEGRF-2 inhibition and the anti-apoptotic effect of the new compounds were determined in liver of irradiated rats. Toxicity of synthesized compounds was also assessed. The results showed that compounds 3-6 have significant antitumor activity and proved to be non-toxic. The ethoxy aniline derivative 6, exhibited the highest activity both in vitro and in vivo compared to the reference drug used, sorafenib. Compound 6 could be considered a promising nontoxic anti HCC agent and this could be partially attributed to its VEGFR-2 inhibition. Future preclinical investigation would be carried out to confirm the specific and exact mechanism of action of these derivatives especially compound 6 as an effective pharmaceutical agent after full toxicological and pharmacological assessment.     

Design,synthesis and activity evaluation of indole-based double – Branched HDAC1 inhibitors

Histone deacetylases inhibitors (HDACIs) represents effective treatments for cancer. In continuing our efforts to develop novel and potent HDACIs, a series of N-hydroxycinnamamide-based HDACIs with aromatic ring and various aliphatic linker have been successfully designed and synthesized. Biological evaluations established that compounds 4h, 4i, 4j, 4l, 4r showed superior inhibition on histone deacetylase and antiproliferative activity in some solid tumor cell lines [HeLa, SK-N-BE(2), PC-3] compared to the known inhibitor SAHA. Among these analogs, 4l exhibited selectivity to HDAC1.     

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.