Inhibitors of src tyrosine kinase: the preparation and structure-activity relationship of 4-anilino-3-cyanoquinolines and 4-anilinoquinazolines

Flavonostilbenes natural hybrids from Rhamnoneuron balansae as potential antitumors targeting ALDH1A1: molecular docking, ADMET, MM-GBSA calculations and molecular dynamics studies

Several studies have linked Cancer stem cells (CSCs) to cancer resistance development to chemotherapy and radiotherapy. ALDH1A1 is a key enzyme that regulates the gene expression of CSCs and creates an immunosuppressive tumor microenvironment. It was reported that quercetin and resveratrol were among the inhibitors of ALDH1A1. In early 2022, it was reported that new 11 flavonostilbenes (rhamnoneuronal D-N) were isolated from Rhamnoneuron balansae as potential antiaging natural products. Rhamnoneuronal H (5) could be envisioned as a natural hybrid of quercetin and resveratrol. It was therefore hypothesized that 5 and its analogous isolates rhamnoneuronal D-G (1-4) and rhamnoneuronal I-N (6-11) would have potential ALDH1A1 inhibitory activity. To this end, all isolates were subjected to molecular docking, MM-GBSA, ADMET, and molecular dynamics simulations studies to assess their potential as new leads for cancer treatment targeting ALDH1A1. In silico findings revealed that natural hybrid 5 has a similar binding affinity, judged by MM-GBSA, to the ALDH1A1 active site when compared to the co-crystalized ligand (-64.71 kcal/mole and -64.12 kcal/mole, respectively). Despite having lesser affinity than that of the co-crystalized ligand, the rest of the flavonostilbenes, except 2-4, displayed better binding affinities (-37.55 kcal/mole to -58.6 kcal/mole) in comparison to either resveratrol (-34.44 kcal/mole) or quercetin (-36.48 kcal/mole). Molecular dynamic simulations showed that the natural hybrids 1, 5-11 are of satisfactory stability up to 100 ns. ADMET outcomes indicate that these hybrids displayed acceptable properties and hence could represent an ideal starting point for the development of potent ALDH1A1 inhibitors for cancer treatment.Communicated by Ramaswamy H. Sarma.

Tunable Regio- and Stereoselective Synthesis of Z-Acrylonitrile Indoles and 3-Cyanoquinolines from 2-Alkynylanilines and Alkynylnitriles

The merger of two bifunctional moieties, 2-alkynylaniline and alkynylnitriles, in the presence of ZnBr₂ offers the tunable synthesis of two biologically important motifs: acrylonitrile indoles and 3-cyanoquinolines. The group present on the terminal alkyne of 2-alkynylaniline regulates the reaction pathways, intra- versus intermolecular, which thereby adds stereoselectivity and regioselectivity in this protocol. The conversion of an acrylonitrile indole ring to quinoline is an intriguing synthetic utility of this methodology.

Synthesis and Evaluation of Novel S-alkyl Phthalimide- and S-benzyl-oxadiazole-quinoline Hybrids as Inhibitors of Monoamine Oxidase and Acetylcholinesterase

New S-alkyl phthalimide 5a-f and S-benzyl 6a-d analogs of 5-(2-phenylquinolin-4-yl)-1,3,4-oxadiazole-2-thiol (4) were prepared by reacting 4 with N-bromoalkylphthalimide and CF₃-substituted benzyl bromides in excellent yields. Spectroscopic techniques were employed to elucidate the structures of the synthesized molecules. The inhibition activity of newly synthesized molecules toward MAO-A, MAO-B, and AChE enzymes, was also assessed. All these compounds showed activity in the submicromolar range against all enzymes. Compounds 5a and 5f were found to be the most potent compounds against MAO-A (IC₅₀ = 0.91 ± 0.15 nM) and MAO-B (IC₅₀ = 0.84 ± 0.06 nM), while compound 5c showed the most efficient acetylcholinesterase inhibition (IC₅₀ = 1.02± 0.65 μM). Docking predictions disclosed the docking poses of the synthesized molecules with all enzymes and demonstrated the outstanding potency of compounds 5a, 5f, and 5c (docking scores = -11.6, -15.3, and -14.0 kcal/mol against MAO-A, MAO-B, and AChE, respectively). These newly synthesized analogs act as up-and-coming candidates for the creation of safer curative use against Alzheimer's illness.

Small Molecule Kinase Inhibitor Drugs (1995-2021): Medical Indication, Pharmacology, and Synthesis

The central role of dysregulated kinase activity in the etiology of progressive disorders, including cancer, has fostered incremental efforts on drug discovery programs over the past 40 years. As a result, kinase inhibitors are today one of the most important classes of drugs. The FDA approved 73 small molecule kinase inhibitor drugs until September 2021, and additional inhibitors were approved by other regulatory agencies during that time. To complement the published literature on clinical kinase inhibitors, we have prepared a review that recaps this large data set into an accessible format for the medicinal chemistry community. Along with the therapeutic and pharmacological properties of each kinase inhibitor approved across the world until 2020, we provide the synthesis routes originally used during the discovery phase, many of which were only available in patent applications. In the last section, we also provide an update on kinase inhibitor drugs approved in 2021.

Design, synthesis, molecular docking and anti-hepatocellular carcinoma evaluation of novel acyclic pyridine thioglycosides

A novel series of acyclic pyridine thioglycosides has been synthesized. Evaluation of the anti proliferative activity of these compounds against HEPG-2 cell lines (liver carcinoma cell lines) shows that most of the compounds have high anti-tumor activities especially 6b, 6c, 7b and 7c. Furthermore, in the modeling study, these compounds showed that they have high binding affinity with thymidylate synthase dihydrofolate reductase (TS-DHFR).

Transetherification of 2,4-dimethoxynitrobenzene by aromatic nucleophilic substitution

In view of the few reports concerning aromatic nucleophilic substitution reactions featuring an alkoxy group as a leaving group, the aromatic nucleophilic substitution of 2,4-dimethoxynitrobenzene was investigated with a bulky t-butoxide nucleophile under microwave irradiation. The transetherification of 2,4-dimethoxynitrobenezene with sodium t-butoxide under specific conditions, namely for 20 min at 110°C in 10% dimethoxyethane in toluene, afforded the desired product in 87% yield with exclusive ortho-selectivity. A variety of reaction conditions were screened to obtain the maximum yield. The aromatic nucleophilic substitution of 2,4-dimethoxynitrobenzene with t-butoxide should be carried out under controlled conditions in order to avoid the formation of byproducts, unlike that of dihalogenated activated benzenes. Among the formed byproducts, a major compound was elucidated as 2,4-dimethoxy-N-(5-methoxy-2-nitrophenyl)aniline by X-ray crystallography.

Apoptosis induction by 7-chloroquinoline-1,2,3-triazoyl carboxamides in triple negative breast cancer cells

Breast cancer is a major public health burden in both developed and developing countries and there is still a need to screen new molecules with different modes of actions. The aims of this study were to evaluate the selectivity profile, apoptotic cell death and cell cycle arrest induced by 7-chloroquinoline-1,2,3-triazoyl carboxamides derivatives in hormonal-dependent and hormonal-independent breast cancer cells. Results showed significantly decreased MCF-7 and MDA-MB-231 cells viability in vitro in a dose dependent manner after treatment with 7-chloroquinoline derivatives QTCA-1, QTCA-2 and QTCA-3. QTCA-1 displayed the highest cytotoxic activity from all the tested compounds in MDA-MB-231 with IC50 values of 20.60, 20.42 and 19.91μM in 24, 48 and 72h of treatment respectively. Apoptosis induction was also significantly higher in the hormonal-independent breast cancer cells, with 80.4% of dead cells in MDA-MB-231 and only 16.8% of dead in MCF-7 cells. As a result, G0/G1 cycle arrest was observed in MCF-7 cells and no cell cycle arrest at all was observed in MDA-MB-231 cells. Molecular docking showed a high affinity of QTCA-1 to PARP-1, Scr and PI3K/mTOR targets. These results suggest a strong activity of the 7-chloroquinoline derivative QTCA-1 in independent-hormonal cells and suggest selectivity for triple negative cells.

A review on anticancer potential of bioactive heterocycle quinoline

The advent of Camptothecin added a new dimension in the field anticancer drug development containing quinoline motif. Quinoline scaffold plays an important role in anticancer drug development as their derivatives have shown excellent results through different mechanism of action such as growth inhibitors by cell cycle arrest, apoptosis, inhibition of angiogenesis, disruption of cell migration, and modulation of nuclear receptor responsiveness. The anti-cancer potential of several of these derivatives have been demonstrated on various cancer cell lines. In this review we have compiled and discussed specifically the anticancer potential of quinoline derivatives, which could provide a low-height flying bird's eye view of the quinoline derived compounds to a medicinal chemist for a comprehensive and target oriented information for development of clinically viable anticancer drugs.

Ligand-based pharmacophore modeling and Bayesian approaches to identify c-Src inhibitors

Abstract Cellular Src (c-Src) kinases play a critical role in cell adhesion, proliferation, angiogenesis and cancer. Ligand-based pharmacophore models, used to identify the critical chemical features of c-Src inhibitors, were generated and validated by training, test and decoy sets, respectively. Best pharmacophore model, Hypo1, consists of four features such as HBA, HBD, Hy-Ar and RA. Hypo1 was used in virtual screening of the chemical databases such as Maybridge, Chembridge and NCI. The sorted compounds by Hypo1 were further reduced by applying drug-like properties and ADMET. Totally, 85 compounds which showed the good drug-like properties were selected from three databases and subjected to molecular docking for refinement of the retrieved hits by analysing the suitable orientation of the compounds in the active site of c-Src. Finally, 18 compounds were selected based on consensus scoring and hydrogen bond interactions with critical amino acids such as Met341, Thr338, Glu339 or Asp404. In addition, the Bayesian model was generated from the training set to find suitable fragments for inhibition of the c-Src function. Based on the above finding, we suggested that the Hypo1 and the good fragments from the Bayesian model will be helpful to select the compounds from various databases to identify the novel and potent c-Src inhibitor.

Synthesis of New 6-{[ω-(Dialkylamino(heterocyclyl)alkyl]thio}-3-R-2H-[1,2,4]triazino[2,3-c]quinazoline-2-ones and Evaluation of their Anticancer and Antimicrobial Activities

Several novel 6-thio-3-R-2-oxo-2H-[1,2,4]triazino[2,3-c]quinazoline-based compounds containing an ω-(dialkylamino(heterocyclyl)]alkyl fragment were synthesized to examine their anticancer activity. Some of the 6-{[ω-(hetero-cyclyl)alkyl]thio}-3-R-2H-[1,2,4]triazino[2,3-c]quinazoline-2-ones (3.1-3.10) were obtained by the nucleophilic substitution of 6-[ω-halogenalkyl]thio-3-R-2H-[1,2,4]triazino[2,3-c]quinazoline-2-ones (2.1-2.8) with azaheterocycles. Alternatively, compounds 3.1-3.22 were synthesized by alkylation of 3-R-6-thio-2H-[1,2,4]triazino[2,3-c]quinazoline-2-ones potassium salts (1.1-1.4) with (2-chloroethyl)-N,N-dialkylamine hydrochlorides or 1-(2-chloroethyl)heterocycle hydrochlorides. The structures of compounds were elucidated by (1)H, (13)C NMR, LC-MS and EI-MS analysis. Then anticancer and antibacterial, bioluminescence inhibition of Photobacterium leiognathi Sh1 activities of the substances were tested in vitro. It was found that compound 3.18 possessed a wide range of anticancer activity against 27 cell lines of cancer: non-small cell lung, colon, CNS, ovarian, renal, prostate, breast, melanoma and leukemia (log GI(50) < -5.65). The "structure-activity" relationship was discussed. COMPARE analysis for synthesized anticancer active compounds was performed.

Synthesis of bosutinib from 3-methoxy-4-hydroxybenzoic acid

This paper reports a novel synthesis of bosutinib starting from 3-methoxy-4-hydroxybenzoic acid. The process starts with esterification of the starting material, followed by alkylation, nitration, reduction, cyclization, chlorination and two successive amination reactions. The intermediates and target molecule were characterized by ¹H-NMR, ¹³C-NMR, MS and the purities of all the compounds were determined by HPLC.

Regioselective one-pot synthesis and anti-proliferative and apoptotic effects of some novel tetrazolo[1,5-a]pyrimidine derivatives

An easy and efficient route for the synthesis of some tetrazolo[1,5-a]-pyrimidine derivatives was described through the reaction of sodium salts of formyl cycloalkanones with 5-aminotetrazole monohydrate. The derivative 6,7,8,9-tetrahydrotetrazolo[1,5-a]quinazoline (6b) has profound anti-tumor cytotoxic effects against Ehrlich ascites carcinoma (EAC) both in vivo and in vitro and against hepatocellular carcinoma (HepG2) cell line in vitro. These anti-tumor effects may be mediated via stimulation of cell cycle arrest and apoptosis through down-regulation of Bcl-2 and up-regulation of p53 transcription factors.

Synthesis and anti-tumor activities of some new pyridines and pyrazolo[1,5-a]pyrimidines

Cyclocondensation of cyanoacetamide, cyanothioacetamide and 3-aminopyrazols with sodium salt of 3-hydroxy-1-(2-naphthyl)prop-2-en-1-one gives pyridin-2-one, pyridin-2(1H)-thione, and pyrazolo[1,5-a]pyrimidine derivatives. These derivatives showed potent anti-tumor cytotoxic activity in vitro using different human cancer cell lines.

Synthesis and bioactivities of 6,7,8-trimethoxy-N-aryl-4-aminoquinazoline derivatives

A series of 4-aminoquinazoline derivatives is prepared by the nucleophilic substitution reaction of 6,7,8-trimethoxy-4-chloroquinazoline and aryl amine. The structures of the compounds are confirmed by elemental analysis, IR, and (1)H NMR spectral data. The compounds are also evaluated for their ability to inhibit tumor cells PC3, A431, Bcap-37, and BGC823 by MTT assays. Among them, 6b and 6e are found as potent inhibitors, with IC(50) values ranging from 5.8 to 9.8microM, in vitro assay.

Identification of a novel class of selective Tpl2 kinase inhibitors: 4-Alkylamino-[1,7]naphthyridine-3-carbonitriles

We have previously reported the discovery and initial SAR of the [1,7]naphthyridine-3-carbonitriles and quinoline-3-carbonitriles as Tumor Progression Loci-2 (Tpl2) kinase inhibitors. In this paper, we report new SAR efforts which have led to the identification of 4-alkylamino-[1,7]naphthyridine-3-carbonitriles. These compounds show good in vitro and in vivo activity against Tpl2 and improved pharmacokinetic properties. In addition they are highly selective for Tpl2 kinase over other kinases, for example, EGFR, MEK, MK2, and p38. Lead compound 4-cycloheptylamino-6-[(pyridin-3-ylmethyl)-amino]-[1,7]naphthyridine-3-carbonitrile (30) was efficacious in a rat model of LPS-induced TNF-alpha production.

Determination of CH330331, a novel 4-anilinoquinazoline inhibitor of epidermal growth factor receptor tyrosine kinase, in human Caco-2 monolayers by high performance liquid chromatography with ultraviolet detection: Application to a trans-epithelial transport study

4-Anilinoquinazolines (e.g. Iressa and Glivec) are a class of epidermal growth factor receptor tyrosine kinase (EGFR-TK) inhibitors widely used to treat non-small cell lung cancer and other tumors. However, low clinical response rate, resistance, and host toxicity of currently available EGFR-TK inhibitors prompt the development of second generation of TK inhibitors with improved efficacy, selectivity, and less resistance. CH330331 is a recently synthesized novel 4-anilinoquinazoline analog with confirmed anticancer activity in vitro and in vivo. To predict its oral pharmacokinetic behavior and transport nature in the intestine before entering clinical trials, we have developed and validated a high performance liquid chromatographic (HPLC) method for the determination of CH330331 in Caco-2 (a human colon cancer cell line) monolayers. The developed HPLC method was sensitive and reliable, with acceptable accuracy (90-110% of nominal values) and precision (intra- and inter-assay R.S.D.<10%). The total running time was within 10 min, with acceptable separation of the target analytes. The lower limit of quantitation (LLOQ) value for CH330331 was 200 ng/ml when an aliquot of 100 microl sample was injected onto the HPLC. The validated HPLC method was applied to characterize the epithelial transport of CH330331 in Caco-2 monolayers. The transport of CH330331 across the Caco-2 monolayers from the apical to basolateral side was 8- to 10-fold higher than that from the basolateral to apical side. Co-incubation of sodium azide or MK-571, but not verapamil, significantly inhibited the apical to basolateral transport of CH330331. These findings provide initial evidence that the intestinal absorption of CH330331 is mediated by an active mechanism. Further studies are required to explore the interaction of CH330331 with ATP-binding cassette transporters and the possible influence on its pharmacokinetics and pharmacodynamics.

Synthesis and bioactivity of 4-alkyl(aryl)thioquinazoline derivatives

Some S'-substituted 4-alkyl(aryl)thioquinazoline derivatives were synthesized through thioetherification reaction of 4-chloroquinazolines 2 and thiol compounds 1 refluxed in acetone in the presence of K(2)CO(3). Their structures were verified by elemental analysis, IR, (1)H NMR, and (13)C NMR. The compounds were evaluated for their anti-proliferative activities against some cancer cells in vitro by MTT method. Among them, 3c, 3a, 3d, 3f, and 3l were highly effective against PC3 cells and 3a-3m showed weak activities against Bcap37 and BGC823 cells. The IC(50) value of 3c, 3a, 3d, 3f, and3l against PC3 cell was 1.8, 5.6, 8.1, 8.7, and 8.9 microM, respectively.

7-(Aryl/heteroaryl-2-ylethynyl)-4-phenylamino-3-quinolinecarbonitriles as new Src kinase inhibitors: Addition of water solubilizing groups

New 4-phenylamino-3-quinolinecarbonitriles with a 7-ethynyl group substituted by a pyridine, phenyl or thiophene ring containing basic water solubilizing groups were prepared and evaluated as Src kinase inhibitors. Of these new analogs, potent activity was observed with compounds having a (2,4-dichloro-5-methoxyphenyl)amino group at C-4, a methoxy or ethoxy group at C-6, and a pyridyl group bearing a dimethylamine or N-methylpiperazine on the ethynyl group at C-7.

3D-QSAR studies on c-Src kinase inhibitors and docking analyses of a potent dual kinase inhibitor of c-Src and c-Abl kinases

Three-dimensional quantitative structure-activity relationship (3D-QSAR) analyses were carried out on quinazoline, quinoline, and cyanoquinoline derivatives inhibiting c-Src kinase. Comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) 3D-QSAR models were developed. The conventional r2 values for CoMFA and CoMSIA are 0.93 and 0.89, respectively. In addition, a homology model of c-Src kinase with the activation loop resembling the active conformation was constructed using the crystal structure of the kinase domain of Lck. The ATP binding pocket of the active form of c-Src is similar to that of the c-Abl kinase in which the activation loop resembles that of an active form. One of the potent c-Src and c-Abl dual kinase inhibitors (77 or SKI-606) was docked inside the active sites of both c-Src and c-Abl. The orientation and hydrogen bonding interactions of 77 are similar in both kinases. The results of 3D-QSAR analyses and structure based studies will be useful for the design of novel c-Src and c-Abl dual kinase inhibitors.

Inhibition of Tpl2 kinase and TNF-alpha production with 1,7-naphthyridine-3-carbonitriles: synthesis and structure-activity relationships

The synthesis and structure-activity studies of a series of 6-substituted-4-anilino-[1,7]-naphthyridine-3-carbonitriles as inhibitors of Tpl2 kinase are described. The early exploratory work described here may lead to the discovery of compounds with significant therapeutic potential for treating rheumatoid arthritis and other inflammatory diseases.

Antiproliferative activity of new 1-aryl-4-amino-1H-pyrazolo[3,4-d]pyrimidine derivatives toward the human epidermoid carcinoma A431 cell line

Synthesis and biological evaluation of a new class of 1-aryl-4-amino-1H-pyrazolo[3,4-d]pyrimidine derivatives are reported. A preliminary cellular assay system using the tumor cell line A431 responding to epidermal growth factor (EGF) for its growth, shows that the new compounds are potent inhibitors of cell growth. The inhibition of tumor cell proliferation is not associated with blockage of EGF receptor (EGFR), but substantially due to the interference with the signalling pathway at the level of Src tyrosine kinase and at the level of the downstream effector signal mitogen activated protein kinases (MAPKs), ERK1-2.

Further studies on ethenyl and ethynyl-4-phenylamino-3-quinolinecarbonitriles: identification of a subnanomolar Src kinase inhibitor

Several new ethynyl- and ethenyl-4-phenylamino-3-quinolinecarbonitriles were synthesized and tested for Src inhibition. Derivatives bearing an ethenyl or ethynyl substituent at C-6 showed decreased Src inhibitory activity. Incorporation of an ethenylpyridine N-oxide group at C-7 provided 20b, a 0.6 nM inhibitor of Src enzymatic activity with excellent cellular potency.

Preparation of kinase-biased compounds in the search for lead inhibitors of kinase targets

This work describes the preparation of approximately 13,000 compounds for rapid identification of hits in high-throughput screening (HTS). These compounds were designed as potential serine/threonine or tyrosine kinase inhibitors. The library consists of various scaffolds, e.g., purines, oxindoles, and imidazoles, whereby each core scaffold generally includes the hydrogen bond acceptor/donor properties known to be important for kinase binding. Several of these are based upon literature kinase templates, or adaptations of them to provide novelty. The routes to their preparation are outlined. A variety of automation techniques were used to prepare >500 compounds per scaffold. Where applicable, scavenger resins were employed to remove excess reagents and when necessary, preparative high performance liquid chromatography (HPLC) was used for purification. These compounds were screened against an 'in-house' kinase panel. The success rate in HTS was significantly higher than the corporate compound collection.

Design and synthesis of aminopropyl tetrahydroindole-based indolin-2-ones as selective and potent inhibitors of Src and Yes tyrosine kinase

A novel series of substituted 3-[3-(aminopropyl)-4,5,6,7-tetrahydro-1H-indol-2-ylmethylene]-1,3-dihydro-indole-2-ones was discovered as potent inhibitors of the non-receptor tyrosine kinase Src and Yes. A structure-activity relationship was developed in order to optimize their potency and selectivity. Syntheses of these compounds are also described herein.

A minimalist approach to fragment-based ligand design using common rings and linkers: Application to kinase inhibitors

We present a novel method for stepwise scaffold assembly that integrates fragment-by-fragment ligand design approaches with high-throughput virtual library screening (COREGEN). As an extension of our earlier studies of common features present in drug molecules, we investigate the hypothesis that most pharmaceutically interesting ligands can be expressed in terms of the ring-linker frameworks that comprise them. Analysis of 119 published kinase inhibitors from at least 18 different targets illustrates that a basis set of 4 rings and 8 linkers is sufficient to describe approximately 90% of ring and linker occurrences, respectively. A similar result was derived from a larger set of approximately 40,000 kinase inhibitors from curated patents. A method for ring-linker-based assembly of scaffold libraries that uses experimental information to guide the placement of anchor fragments is validated using a set of reported kinase inhibitors of Bcr-Abl, Cdk2, and Src. In every case, the predominant structural motif of reported ligand cores is reproduced and variations are suggested. To underscore generality of this approach, a novel scaffold for a cyclooxygenase-2 (COX-2) selective ligand is proposed.

Investigation of the effect of varying the 4-anilino and 7-alkoxy groups of 3-quinolinecarbonitriles on the inhibition of Src kinase activity

Several 7-alkoxy-4-anilino-3-quinolinecarbonitriles were synthesized and evaluated for Src kinase inhibitory activity. Optimal inhibition of both Src enzymatic and cellular activity was seen with analogues having a 2,4-dichloro-5-methoxyaniline group at C-4. Compound 18, which has a 1-methylpiperidinemethoxy group at C-7, showed in vivo activity in a xenograft model.

Inhibition of Src kinase activity by 4-anilino-5,10-dihydro-pyrimido[4,5-b]quinolines

4-(2,4-Dichloro-5-methoxy)anilino-5,10-dihydropyrimido[4,5-b]quinolines are potent inhibitors of Src kinase and Src cellular activity while having no effect on Fyn cellular activity. The corresponding 4-(2,4-dichloro-5-methoxy)anilino-pyrimido[4,5-b]quinolines are much less effective Src inhibitors.

Syntheses and EGFR and HER-2 kinase inhibitory activities of 4-anilinoquinoline-3-carbonitriles: analogues of three important 4-anilinoquinazolines currently undergoing clinical evaluation as therapeutic antitumor agents

The syntheses and biological evaluations of 4-anilinoquinoline-3-carbonitrile analogues of the three clinical lead 4-anilinoquinazolines Iressa, Tarceva, and CI-1033 are described. The EGFR and HER-2 kinase inhibitory activities and the cell growth inhibition of the two series are compared with each other and with the clinical lead EKB-569. Similar activities are observed between these two series.

8-Anilinoimidazo[4,5-g]quinoline-7-carbonitriles as Src kinase inhibitors

A series of 8-anilinoimidazo[4,5-g]quinoline-7-carbonitriles was synthesized and evaluated as Src kinase inhibitors. Several aniline substituents were surveyed, as well as water-solubilizing groups at the C-2 and N-3 positions. Potent Src inhibitors were identified, with N-3 providing the best position for an additional water-solubilizing group.

Substituted 4-anilino-7-phenyl-3-quinolinecarbonitriles as Src kinase inhibitors

A series of substituted 4-anilino-7-phenyl-3-quinolinecarbonitriles has been prepared as Src kinase inhibitors. Optimal activity is observed with compounds that have basic amines attached via the para position of the 7-phenyl ring, and a hydrogen atom at the C-6 position. The best compounds are low nanomolar inhibitors of Src kinase, and have potent activity against Src-transformed fibroblast cells.

Inhibition of Src kinase activity by 4-anilino-7-thienyl-3-quinolinecarbonitriles

Based on a screening lead from a yeast-based assay to identify Src family kinase inhibitors, a series of 4-anilino-7-thienyl-3-quinolinecarbonitriles was prepared. When the thiophene ring was substituted with a water-solubilizing group in a 2,5-, 3,5- or 2,4-pattern, potent inhibition of Src kinase activity was observed.

4-Anilino-3-cyanobenzo[g]quinolines as kinase inhibitors

A series of 4-anilino-3-cyanobenzo[g]quinolines was prepared as potent kinase inhibitors. Compared with their bicyclic 4-anilino-3-cyanoquinoline analogues, the tricyclic 4-anilino-3-cyanobenzo[g]quinolines are less active against EGF-R kinase, equally active against MAPK kinase (MEK), and more active against Src kinase. For Src kinase inhibition, the best activity is obtained when both the 7- and 8-positions are substituted with alkoxy groups. Several of these kinase inhibitors show potent growth inhibitory activity in tumor cells.

Src inhibitors: genomics to therapeutics

Following the milestone discoveries that identified Src as the first known protein tyrosine kinase and as a prototype oncogene, as well as Src transgenic studies to validate it as a promising therapeutic target for osteoporosis, intense efforts are being made to create Src inhibitor drugs. Drug discovery strategies focused on both the non-catalytic and catalytic domains of Src have successfully resulted in promising Src inhibitor lead compounds with potential therapeutic applications for osteoporosis, cancer, and other diseases. Some noteworthy examples of Src inhibitors are described, and their chemical diversity, structure-based design, and biological activities in vitro and in vivo are illustrated. The potency, selectivity, and in vivo efficacy of key Src inhibitors are being investigated in molecular, cellular and animal models. Consequently, Src inhibitor drug development is imminent, and current studies are well-poised to achieve the ultimate milestone of a Src inhibitor therapeutic.

MEK (MAPKK) inhibitors. Part 2: structure–activity relationships of 4-anilino-3-cyano-6,7-dialkoxyquinolines

A series of 4-anilino-3-cyano-6,7-dialkoxyquinolines with different substituents attached to the 4-anilino group has been prepared that are potent MEK (MAP kinase kinase) inhibitors. The best activity is obtained when a phenyl or a thienyl group is attached to the para-position of the aniline through a hydrophobic linker, such as an oxygen, a sulfur, or a methylene group. The most active compounds show low nanomolar IC(50)'s against MEK (MAP kinase kinase), and have potent growth inhibitory activity in LoVo cells (human colon tumor line).

7-Alkyl- and 7-cycloalkyl-5-aryl-pyrrolo[2,3-d]pyrimidines--potent inhibitors of the tyrosine kinase c-Src

7-Substituted-5-aryl-pyrrolo[2,3-d]pyrimidines have been prepared starting from alpha-bromoacetophenones. These compounds represent a novel class of potent inhibitors of the tyrosine kinase pp60(c-Src) with good specificity towards other tyrosine kinases (EGF-R, v-Abl).

Novel antitumour molecules

Monitor provides an insight into the latest developments in drug discovery through brief synopses of recent presentations and publications together with expert commentaries on the latest technologies. There are two sections: Molecules summarizes the chemistry and the pharmacological significance and biological relevance of new molecules reported in the literature and on the conference scene; Profiles offers commentary on promising lines of research, emerging molecular targets, novel technology, advances in synthetic and separation techniques and legislative issues.