Expanding the structural diversity of diarylureas as multi-target tyrosine kinase inhibitors

Recently approved multi-target inhibitors of receptor tyrosine kinases (RTKs) have significantly improved the clinical treatment of cancers. A series of N,N′-diarylureas incorporated with aromatic heterocycle have been designed, synthesized and evaluated as novel multi-target RTK inhibitors. The preliminary biological evaluation indicated that several compounds exhibited comparable potency with Sorafenib. Among them, compound 6f was identified as the most potent multikinase inhibitor of EGFR, KDR and FGFR1 with IC₅₀ values of 14.83 nM, 21.57 nM, and 28.23 nM, respectively. These compounds expanded the structural diversity of diarylureas as RTK inhibitors. The results demonstrated that compound 6f could be served as novel lead compound for further development of multi-target RTK inhibitors.     

Design,synthesis and evaluate of novel dual FGFR1 and HDAC inhibitors bearing an indazole scaffold

Both histone deacetylase (HDAC) and fibroblast growth factor receptor (FGFR) are important targets for cancer therapy. Although combining dual HDAC pharmacophore with tyrosine kinase inhibitors (TKIs) had achieved a successful progress, dual HDAC/FGFR1 inhibitors haven’t been reported yet. Herein, we designed a series of hybrids bearing 1H-indazol-3-amine and benzohydroxamic acids scaffold with scaffold hopping and molecular hybridization strategies. Among them, compound 7j showed the most potent inhibitory activity against HDAC6 with IC₅₀ of 34?nM and exhibited the great inhibitory activities against a human breast cancer cell line MCF-7 with IC₅₀ of 9?μM in vitro. Meanwhile, the compound also exhibited moderate FGFR1 inhibitory activities. This study provides new tool compounds for further exploration of dual HDAC/FGFR1 inhibition.     

Discovery of novel tetracyclic compounds as anaplastic lymphoma kinase inhibitors

Anaplastic lymphoma kinase (ALK) receptor tyrosine kinase is considered a promising therapeutic target for human cancers. We identified novel tetracyclic derivatives as potent ALK inhibitors. Among them, compound 27 showed strong cytotoxicity against KARPAS-299 with an IC₅₀ value of 21 nM and significant antitumor efficacy in ALK fusion-positive blood and solid cancer xenograft models in mice without body weight loss.     

Discovery of thiazolidin-4-one urea analogues as novel multikinase inhibitors that potently inhibit FLT3 and VEGFR2

A series of novel thiazolidine-4-one urea analogues were designed, synthesized and biologically evaluated. The structure-activity relationship (SAR) at several positions of the scaffolds was investigated and its binding mode was analyzed by molecular modeling studies. Compound 17b proved to be the most potent one, and IC₅₀ values against A549 and HT-29 cancer cell lines were 0.65?μM and 0.11?μM, respectively. The results of kinase profile demonstrated that compound 17b is a multikinase inhibitor that potently inhibits FLT3 (IC₅₀?=?8.6?nM) and VEGFR2 (IC₅₀?=?18.7?nM). The results of real-time live-cell imaging indicated that compound 17b showed excellent cytotoxicity and anti-proliferative activity against HT-29 cancer cells in a time- and dose-dependent manner, which was significantly potent than that of Cabozantinib. In addition, in vitro antitumor activity was associated with inducing cancer cell apoptosis and suppression of cancer cell migration.     

Discovery of novel selective Janus kinase 2 (JAK2) inhibitors bearing a 1H-pyrazolo[3,4-d]pyrimidin-4-amino scaffold

Janus kinases (JAKs) regulate various cancers and immune responses and are targets for the treatment of cancers and immune diseases. A new series of 1H-pyrazolo[3,4-d]pyrimidin-4-amino derivatives were synthesized and optimized by introducing a functional 3,5-disubstituted-1H-pyrazole moiety into the C-3 moiety of pyrazole template, and then were biologically evaluated as potent Janus kinase 2 (JAK2) inhibitors. Among these molecules, inhibitors 11f, 11g, 11h and 11k displayed strong activity and selectivity against the JAK2 kinase, with IC₅₀ values of 7.2?nM, 6.5?nM, 8.0?nM and 9.7?nM, respectively. In particular, the cellular inhibitory assay and western blot analysis further support the JAK2 selectivity of compound 11g also in cells. Furthermore, compound 11g also exhibited potent inhibitory activity in lymphocytes proliferation assay and delayed hypersensitivity assay. Taken together, the novel JAK2 selective inhibitors discovered in this study may be potential lead compounds for new drug discovery via further development of more potent and selective JAK2 inhibitors.     

Imidazo[1,2-a]pyrazine diaryl ureas: Inhibitors of the receptor tyrosine kinase EphB4

Inhibition of receptor tyrosine kinases (RTKs) such as vascular endothelial growth factor receptors (VEGFRs) and platelet-derived growth factor receptors (PDGFRs) has been validated by recently launched small molecules Sutent^® and Nexavar^®, both of which display activities against several angiogenesis-related RTKs. EphB4, a receptor tyrosine kinase (RTK) involved in the processes of embryogenesis and angiogenesis, has been shown to be aberrantly up regulated in many cancer types such as breast, lung, bladder and prostate. We propose that inhibition of EphB4 in addition to other validated RTKs would enhance the anti-angiogenic effect and ultimately result in more pronounced anti-cancer efficacy. Herein we report the discovery and SAR of a novel series of imidazo[1,2-a]pyrazine diarylureas that show nanomolar potency for the EphB4 receptor, in addition to potent activity against several other RTKs.     

Discovery of N-aryl-N′-pyrimidin-4-yl ureas as irreversible L858R/T790M mutant selective epidermal growth factor receptor inhibitors

A novel series of N-aryl-N′-pyrimidin-4-yl ureas has been optimized to afford potent and selective inhibitors of the EGFR L858R/T790M. The most representative compound 28 showed high activity against EGFR L858R/T790M kinase (IC₅₀?=?4?nM) and 22-fold selectivity against wild type EGFR. Moreover, compound 28 potently inhibited EGFR L858R/T790M phosphorylation (IC₅₀?=?41?nM) and cellular proliferation (IC₅₀?=?37?nM) in the H1975 cell line, while being significantly less toxic to A431 cells. Further, compound 28 exhibited a great selectivity in a mini-panel of kinases.     

Synthesis and biological evaluation of novel oxindole-based RTK inhibitors as anti-cancer agents

Given that receptor tyrosine kinases (RTKs) have emerged as key regulators of all aspects of cancer development, including proliferation, invasion, angiogenesis and metastasis, the RTK family represents an important therapeutic target for anti-cancer drug development. Oxindole structure has been used in RTK inhibitors such as SU4984 and intedanib. In this study, two series of new heterocyclic compounds containing oxindole scaffold have been designed and synthesized, and their inhibitory activity against the proliferation of nine cancer cell lines has been evaluated. Among them, compounds 9a and 9b displayed the strongest anti-proliferative activity with the IC₅₀s below 10 μM. Flow cytometric analysis showed that the compounds 9a and 9b dose-dependently arrested the cell cycle at G0/G1 phase. Although the leading compounds SU4984 and intedanib targets FGFR1, the kinase activity test revealed that these compounds only showed slight inhibitory activity on FGFR1 kinase. Further enzymatic test aided by molecular docking simulation in the ATP-binding site demonstrated that 9a and 9b are potent inhibitors of c-Kit kinase. These compounds are worthy of further evaluation as anticancer agents.     

Design,synthesis, and biological evaluation of 4-((6,7-dimethoxyquinoline-4-yl)oxy)aniline derivatives as FLT3 inhibitors for the treatment of acute myeloid leukemia

FMS-like tyrosine kinase 3 (FLT3) was an important therapeutic target in acute myeloid leukemia (AML). We synthesized two series of 4-((6,7-dimethoxyquinoline-4-yl)oxy)aniline derivatives possessing the semicarbazide moiety and 2,2,2-trifluoro-N,N′-dimethylacetamide moiety as the linker. The cell proliferation assay in vitro against HL-60 and MV4-11 cell lines demonstrated that most series I compounds containing semicarbazide moiety had more potent than Cabozantinib. Furthermore, the enzyme assay showed that compound 12c and 12g were potent FLT3 inhibitors with IC₅₀ values of 312 nM and 384 nM, respectively. Following that, molecular docking analysis was also performed to determine possible binding mode between FLT3 and the target compound.     

Radioiodinated sunitinib as a potential radiotracer for imaging angiogenesis-radiosynthesis and first radiopharmacological evaluation of 5-[125I]Iodo-sunitinib

Sunitinib® (SU11248) is a highly potent tyrosine kinase inhibitor targeting vascular endothelial growth factor receptor (VEGFR). Radiolabeled inhibitors of RTKs might be useful tools for monitoring RTKs levels in tumour tissue giving valuable information for anti-angiogenic therapy. We report here the synthesis of a ¹²⁵I-labeled derivative of sunitinib® and its first radiopharmaceutical characterization.The non-radioactive reference compound 5-iodo-sunitinib 4 was prepared by Knoevenagel condensation of 5-iodo-oxindole with the corresponding substituted 5-formyl-1H-pyrrole. In a competition binding assay against VEGFR-2 a binding constant (K_d) of 16 nM for 4 was found. The ability of 4 to inhibit tyrosine kinase activity was demonstrated on RTK expressing cells suggesting this radiotracer as a useful tool for monitoring VEGFR expression. 5-[¹²⁵I]lodo-sunitinib, [¹²⁵I]-4 was obtained via destannylation of the corresponding tributylstannyl precursor with [¹²⁵I]NaI in the presence of H₂O₂ in high radiochemical yield (>95%) and radiochemical purity (<98%) after HPLC purification. Determination of human plasma protein binding at time intervals of 0; 1; 2; 4 and 24 h suggested a low non-specific binding of 5-10%. Preliminary biodistribution studies of [¹²⁵I]-4 in healthy CD-1 mice showed a relatively high uptake in VEGFR-2 rich tissues like kidney and lung followed by rapid washout (9.6 and 9.7; 4.5 and 3.8% ID/g of kidney and lung at 1 and 4 h, respectively).     

Design and synthesis of benzofuro[3,2-b]pyridin-2(1H)-one derivatives as anti-leukemia agents by inhibiting Btk and PI3Kδ

Btk inhibitors and PI3Kδ inhibitors play crucial roles in the treatment of leukemia, and studies confirmed that the synergetic inhibition against Btk and PI3Kδ could gain an optimal response. Herein, a series of novel benzofuro[3,2-b]pyridin-2(1H)-one derivatives were designed and synthesized as dual Btk/PI3Kδ kinases inhibitors for the treatment of leukemia. Studies indicated that most compounds could suppress the proliferation of multiple leukemia or lymphoma cells (Raji, HL60 and K562 cells) at low micromolar concentrations in vitro. Further kinase assays identified several compounds could simultaneously inhibit Btk kinase and PI3Kδ kinase. Thereinto, compound 16b exhibited the best inhibitory activity (Btk: IC₅₀?=?139?nM; PI3Kδ: IC₅₀?=?275?nM) and showed some selectivity against PI3Kδ compared to PI3Kβ/γ. Finally, the SAR of target compounds was preliminarily discussed combined with docking results. In brief, 16b possessed of the potency for the further optimization as anti-leukemia drugs by inhibiting simultaneously Btk kinase and PI3Kδ kinase.     

Tyrosine kinase inhibition effects of novel Pyrazolo[1,5-a]pyrimidines and Pyrido[2,3-d]pyrimidines ligand: Synthesis,biological screening and molecular modeling studies

Tyrosine kinases are one of the most critical mediators in the signaling path way. Late studies have proved the part of tyrosine kinases in the pathophysiology of cancer diseases. This current research paper has focused on investigating the novel Pyrazolo[1,5-a]pyrimidines and Pyrido[2,3-d]pyrimidines as a small molecules that can inhibit tyrosine kinase in cancer cells. NCI protocol was applied to test the antitumor activity of such compounds. Leukemia and renal cancer cell lines proved to be sensitive to some derivatives such as 6b–d, 9a and 11 with GI% values ranging from 30.4 to 41.3%. In addition, compound 11 proved to be the most active against MCF-7 with GI% 62.5. The synthesized compounds were also evaluated for their inhibitory effects against EGFR kinase enzyme. Compound 9b proved to be the most active one among the synthesized series with inhibition % value of 81.72 at 25 nM concentration and IC₅₀ 8.4 nM which is very close to the reference drug Sorafenib. In vitro cytotoxicity test was also performed using the MCF-7 breast cell line. Computer modeling using the active site of tyrosine kinase as a template and the most active tyrosine kinase inhibitors were calculated. Docking studies of the synthesized compounds into the active site of EGFR kinase domain showed good agreement with the obtained biological results.     

Synthesis of DNA interactive C3-trans-cinnamide linked β-carboline conjugates as potential cytotoxic and DNA topoisomerase I inhibitors

A series of new C3-trans-cinnamide linked β-carboline conjugates has been synthesized by coupling between various β-carboline amines and substituted cinnamic acids. Evaluation of their anti-proliferative activity against a panel of selected human cancer cell lines such as A549 (lung cancer), MCF-7 (breast cancer), B16 (melanoma), HeLa (cervical cancer) and a normal cell line NIH3T3 (mouse embryonic fibroblast cell line), suggested that the newly designed conjugates are considerably active against all the tested cancer cell lines with IC₅₀ values 13–45?nM. Moreover, the conjugates 8v and 8x were the most active against MCF-7 cells (14.05?nM and 13.84?nM respectively) and also even potent on other cell lines tested. Further, detailed investigations such as cell cycle analysis, apoptosis induction study, topoisomerase I inhibition assay, DNA binding affinity and docking studies revealed that these new conjugates are DNA interactive topoisomerase I inhibitors.     

Rational modification of semaxanib and sunitinib for developing a tumor growth inhibitor targeting ATP binding site of tyrosine kinase

Analysis of the crystal structure of tyrosine kinase in complexation with an ATP analogue, supplemented with the molecular docking studies of semaxanib and sunitinib in the ATP binding site of the enzyme enabled us to make design of a series of tyrosine kinase inhibitors. The combination of pyrrole and indolinone in one molecule and placement of appropriate substituent thereof made the molecule compatible for the hydrophobic sub-pocket of the enzyme. Screening of the compounds over 60 cell line panel of human tumor cell lines identified compound 3a that exhibited GI₅₀ 35?nM and 63?nM against MCF7 and MDA-MB-468 cell lines of breast cancer.     

Design,synthesis, biological evaluation and cellular imaging of imidazo[4,5-b]pyridine derivatives as potent and selective TAM inhibitors

The TAM kinase family arises as a new effective and attractive therapeutic target for cancer therapy, autoimmune and viral diseases. A series of 2,6-disubstituted imidazo[4,5-b]pyridines were designed, synthesized and identified as highly potent TAM inhibitors. Despite remarkable structural similarities within the TAM family, compounds 28 and 25 demonstrated high activity and selectivity in vitro against AXL and MER, with IC₅₀ value of 0.77?nM and 9?nM respectively and a 120- to 900-fold selectivity. We also observed an unexpected nuclear localization for compound 10Bb, thanks to nanoSIMS technology, which could be correlated to the absence of cytotoxicity on three different cancer cell lines being sensitive to TAM inhibition.     

Design and discovery of thioether and nicotinamide containing sorafenib analogues as multikinase inhibitors targeting B-Raf,B-RafV600E and VEGFR-2

New sorafenib derivatives containing thioether and nicotinamide moiety were designed and synthesized as B-Raf, B-Raf^V600E and VEGFR-2 multikinase inhibitors. Their in vitro enzymatic inhibitory activities against B-Raf, B-Raf^V600E and VEGFR-2 and their antiproliferative activities against HCT-116 and B16BL6 cell lines were evaluated and described. Most of the compounds showed potent activities against both cell lines and specific kinases. Compounds a1, b1 and c4, which exhibited the most potent inhibitory activities against B-Raf with IC₅₀ of 21?nM, 27?nM and 17?nM, B-Raf^V600E with IC₅₀ of 29?nM, 28?nM and 16?nM, VEGFR-2 with IC₅₀ of 84?nM, 46?nM and 63?nM, respectively, and good antiproliferative activities, also demonstrated competitive antiangiogenic activities to sorafenib in in vitro HUVEC tube formation assay.     

Structure-based design and synthesis of 1H-pyrazolo[3,4-d]pyrimidin-4-amino derivatives as Janus kinase 3 inhibitors

Janus kinases (JAKs) regulate various inflammatory and immune responses and are targets for the treatment of inflammatory and immune diseases. Here we report the discovery and optimization of 1H-pyrazolo[3,4-d]pyrimidin-4-amino as covalent JAK3 inhibitors that exploit a unique cysteine (Cys909) residue in JAK3. Our optimization study gave compound 12a, which exhibited potent JAK3 inhibitory activity (IC₅₀ of 6.2?nM) as well as excellent JAK kinase selectivity (>60-fold). In cellular assay, 12a exhibited potent immunomodulating effect on IL-2-stimulated T cell proliferation (IC₅₀ of 9.4?μM). Further, compound 12a showed efficacy in delayed hypersensitivity assay. The data supports the further investigation of these compounds as novel JAKs inhibitors.     

Design,synthesis and biological evaluation of pyridone–aminal derivatives as MNK1/2 inhibitors

Excessive phosphorylation of eukaryotic translation initiation factor 4E (eIF4E) plays a major role in the dysregulation of mRNA translation and the activation of tumor cell signaling. eIF4E is exclusively phosphorylated by mitogen-activated protein kinase interacting kinases 1 and 2 (MNK1/2) on Ser209. So, MNK1/2 inhibitors could decrease the level of p-eIF4E and regulate tumor-associated signaling pathways. A series of pyridone–aminal derivatives were synthesized and evaluated as MNK1/2 inhibitors. Several compounds exhibited great inhibitory activity against MNK1/2 and selected compounds showed moderate to excellent anti-proliferative potency against hematologic cancer cell lines. In particular, compound 42i (MNK1 IC₅₀?=?7.0?nM; MNK2 IC₅₀?=?6.1?nM) proved to be the most potent compound against TMD-8 cell line with IC₅₀ value of 0.91?μM. Furthermore, 42i could block the phosphorylation level of eIF4E in CT-26 cell line, and 42i inhibited the tumor growth of CT-26 allograft model significantly. These results indicated that compound 42i was a promising MNK1/2 inhibitor for the potent treatment of colon cancer.     

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.     

Discovery and development of substituted tyrosine derivatives as Bcl-2/Mcl-1 inhibitors

Anti-apoptotic Bcl-2 family proteins are vital for cancer cells to escape apoptosis, which make them attractive targets for cancer therapy. Recently, a lead compound 1 was found to modestly inhibit the binding of BH3 peptide to Bcl-2 protein with a K_i value of 5.2?µM. Based on this, a series of substituted tyrosine derivatives were developed and tested for their binding affinities to Bcl-2 protein. Results indicated that these compounds exhibited potent binding affinities to Bcl-2 and Mcl-1 protein but not to Bcl-X_L protein. Promisingly, compound 6i inhibited the binding of BH3 peptide to Bcl-2 and Mcl-1 protein with a K_i value of 450 and 190?nM respectively, and showed obvious anti-proliferative activities against tested cancer cells.