Tyrosine kinase inhibitors. 8. An unusually steep structure-activity relationship for analogues of 4-(3-bromoanilino)-6,7-dimethoxyquinazoline (PD 153035), a potent inhibitor of the epidermal growth factor receptor

Generative and reinforcement learning approaches for the automated de novo design of bioactive compounds

Deep generative neural networks have been used increasingly in computational chemistry for de novo design of molecules with desired properties. Many deep learning approaches employ reinforcement learning for optimizing the target properties of the generated molecules. However, the success of this approach is often hampered by the problem of sparse rewards as the majority of the generated molecules are expectedly predicted as inactives. We propose several technical innovations to address this problem and improve the balance between exploration and exploitation modes in reinforcement learning. In a proof-of-concept study, we demonstrate the application of the deep generative recurrent neural network architecture enhanced by several proposed technical tricks to design inhibitors of the epidermal growth factor (EGFR) and further experimentally validate their potency. The proposed technical solutions are expected to substantially improve the success rate of finding novel bioactive compounds for specific biological targets using generative and reinforcement learning approaches.

Optical spectra and conformation pool of tyrosine kinase inhibitor PD153035 using a robust quantum mechanical conformation search

The most potent drug configuration is not necessarily the lowest energy conformer. The optical spectral profile of a flexible TKI depends on the distribution of the conformers and therefore the conditions such as environment (solvent).

Tyrosine kinase inhibitor prodrug-loaded liposomes for controlled release at tumor microenvironment

Tyrosine kinase inhibitors (TKIs) represent one of the most advanced class of therapeutics for cancer treatment. Most of them are also cytochrome P450 (CYP) inhibitors and/or substrates thereof. Accordingly, their efficacy and/or toxicity can be affected by CYP-mediated metabolism and by metabolism-derived drug-drug interactions. In order to enhance the therapeutic performance of these drugs, we developed a prodrug (Pro962) of our TKI TK962 specifically designed for liposome loading and pH-controlled release in the tumor. A cholesterol moiety was linked to TK962 through pH-sensitive hydrazone bond for anchoring to the liposome phospholipid bilayer to prevent leakage of the prodrug from the nanocarrier. Bioactivity studies performed on isolated target kinases showed that the prodrug maintains only partial activity against them and the release of TK962 is required. Biopharmaceutical studies carried out with prodrug loaded liposomes showed that the prodrug was firmly associated with the vesicles and the drug release was prevented under blood-mimicking conditions. Conversely, conventional liposome loaded with TK962 readily released the drug. Flow cytometric studies showed that liposomes efficiently provided for intracellular prodrug delivery. The use of the hydrazone linker yielded a pH-controlled drug release, which resulted in about 50% drug release at pH 4 and 5 in 2 h. Prodrug, prodrug loaded liposomes and active lead compound have been tested against cancer cell lines in either 2D or 3D models. The liposome formulation showed higher cytotoxicity than the unformulated lead TK962 in both 2D and 3D models. The stability of prodrug, prodrug loaded liposomes and active lead compound in human serum and against human, mouse, and rat microsomes was also assessed, demonstrating that liposome formulations impair the metabolic reactions and protect the loaded compounds from catabolism. The results suggest that the liposomal formulation of pH releasable TKI prodrugs is a promising strategy to improve the metabolic stability, intracellular cancer cell delivery and release, and in turn the efficacy of this class of anticancer drugs.

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.

Quinazoline-tethered hydrazone: A versatile scaffold toward dual anti-TB and EGFR inhibition activities in NSCLC

Globally, lung cancer and tuberculosis are considered to be very serious and complex diseases. Evidence suggests that chronic infection with tuberculosis (TB) can often lead to lung tumors; therefore, developing drugs that target both diseases is of great clinical significance. In our study, we designed and synthesized a suite of 14 new quinazolinones (5a-n) and performed biological investigations of these compounds in Mycobacterium tuberculosis (MTB) and cancer cell lines. In addition, we conducted a molecular modeling study to determine the mechanism of action of these compounds at the molecular level. Compounds that showed anticancer activity in the preliminary screening were further evaluated in three cancer cell lines (A549, Calu-3, and BT-474 cells) and characterized in an epidermal growth factor receptor (EGFR) binding assay. Cytotoxicity in noncancerous lung fibroblast cells was also evaluated to obtain safety data. Our theoretical and experimental studies indicated that our compounds showed a mechanism of action similar to that of erlotinib by inhibiting the EGFR tyrosine kinase. In turn, the antituberculosis activity of these compounds would be produced by the inhibition of enoyl-ACP-reductase. From our findings, we were able to identify two potential lead compounds (5i and 5l) with dual activity and elevated safety toward noncancerous lung fibroblast cells. In addition, our data identified three compounds with excellent anti-TB activities (compounds 5i, 5l, and 5n).

Synthesis and Anti-Proliferation Activity Evaluation of Novel 2-Chloroquinazoline as Potential EGFR-TK Inhibitors

A novel series of 2-chloroquinazoline derivatives had been synthesized and their anti-proliferation activities against the four EGFR high-expressing cells A549, NCI-H1975, AGS and HepG2 cell lines were evaluated. The preliminary SAR study of the scaffold of new compounds showed that the compounds with a chlorine substituent on R³ had a better anti-proliferation activity than those substituted by hydrogen atom or vinyl group. Among them, 2-chloro-N-[2-chloro-4-(3-chloro-4-fluoroanilino)quinazolin-6-yl]acetamide (10b) had the best activity, and the corresponding IC₅₀ were 3.68, 10.06, 1.73 and 2.04 μM, respectively. And compound 10b had better or equivalent activity against four cell lines than Gefitinib. The activity of the compound 10b on the EGFR enzyme was subsequently tested. The Wound Healing of A549, AGS and HepG2 cells by this compound showed that the compound can inhibit the migration of cancer cells. Finally, the action channel of the compound 10b was supported by western blotting experiments. It provides useful information for the design of EGFR-TK inhibitors.

Bestowal of Quinazoline Scaffold in Anticancer Drug Discovery

BACKGROUND

Cancer is one of the major causes of human mortality worldwide. A number of existing antineoplastic medications and treatment regimens are already working in the field, and several new compounds are in different phases of clinical trials. An extensive series of anticancer drugs exist in the market, and studies suggest that these molecules are associated with different types of adverse side effects. The reduction of the cytotoxicity of drugs to normal cells is a major problem in anticancer therapy. Therefore, researchers around the globe are involved in the development of more efficient and safer anticancer drugs. The output of extensive research is that the quinazoline scaffold and its various derivatives can be explored further as a novel class of cancer chemotherapeutic agents that has already shown promising activities against different tumours. Quinazoline derivatives have already occupied a crucial place in modern medicinal chemistry. Various research has been performed on quinazoline and their derivatives for anticancer activity and pharmacological importance of this scaffold has been well established.

OBJECTIVE

The aim of this review is to compile and highlight the developments concerning the anticancer activity of quinazoline derivatives as well as to suggest some new aspects of the expansion of anticancer activity of novel quinazoline derivatives as anticancer agents in the near future.

METHODS

Recent literature related to quinazoline derivatives endowed with encouraging anticancer potential is reviewed. With a special focus on quinazoline moiety, this review offers a detailed account of multiple mechanisms of action of various quinazoline derivatives: inhibition of the DNA repair enzyme system, inhibition of EGFR, thymidylate enzyme inhibition and inhibitory effects for tubulin polymerization by which these derivatives have shown promising anticancer potential.

RESULTS

Exhaustive literature survey indicated that quinazoline derivatives are associated with properties of inhibiting EGFR and thymidylate enzymes. It was also found to be involved in disturbing tubulin assembly. Furthermore, quinazoline derivatives have been found to inhibit critical targets such as DNA repair enzymes. These derivatives have shown significant activity against cancer.

CONCLUSION

In cancer therapy, Quinazoline derivatives seems to be quite promising and act through various mechanisms that are well established. This review has shown that quinazoline derivatives can further be explored for the betterment of chemotherapy. A lot of potentials are still hidden, which demands to be discovered for upgrading quinazoline derivatives efficacy.

Potential of substituted quinazolines to interact with multiple targets in the treatment of cancer

The efficacy of quinazoline-based antiglioma agents has been attributed to their effects on microtubule dynamics.1,2 The design, synthesis and biological evaluation of quinazolines as potent inhibitors of multiple intracellular targets, including microtubules and multiple RTKs, is described. In addition to the known ability of quinazolines 1 and 2 to cause microtubule depolymerization, they were found to be low nanomolar inhibitors of EGFR, VEGFR-2 and PDGFR-β. Low nanomolar inhibition of EGFR was observed for 1-3 and 9-10. Compounds 1 and 4 inhibited VEGFR-2 kinase with activity better than or equal to that of sunitinib. In addition, compounds 1 and 2 had similar potency to sunitinib in the CAM angiogenesis assay. Multitarget activities of compounds in the present study demonstrates that the quinazolines can affect multiple pathways and could lead to these agents having antitumor potential caused by their activity against multiple targets.

Switchable and efficient conversion of 2-amido-aryl oxazolines to quinazolin-4(3H)-ones and N-(2-chloroethyl)benzamides

Switchable chemoselective conversion of 2-amido-aryl oxazolines to quinazolin-4(3H)-ones or N-(2-chloroethyl)benzamides is achieved.

Cu-Catalyzed Direct Amination of Cyclic Amides via C-OH Bond Activation Using DMF

Herein, we describe a Cu-catalyzed approach to directly accessing aromatic heterocyclic amines from cyclic amides. The most-reported methods for cyclic amide conversions to aromatic heterocyclic amines use an activating group, such as a halogen atom or a trifluoromethane sulfonyl group. However, subsequent elimination of activating groups during the amination process results in significant waste. This copper-catalyzed direct amination of cyclic amides in DMF forms aromatic heterocyclic amines with environmental friendliness and readily available reagents. A plausible radical mechanism has been proposed for the reaction. Meanwhile, the coordinating effect of the N1 atom is key to the success of this reaction, which provides assistance to the copper ions for the activation and amination of C-O bonds.

Synthesis and Spectral Characterization of 4,7-Dichloro-6-nitroquinazoline

Afatinib is a 4-anilinoquinazoline tyrosine kinase inhibitor (TKI) in the form of a dimaleate salt which is indicated for the treatment of locally advanced or metastatic non-small cell lung cancer (NSCLC). The most scalable route for the synthesis of this drug was reported in two Boehringer Ingelheim patents, in which the title compound, 4,7-dichloro-6-nitroquinazoline (IV), is an important intermediate. Compound IV is also present in a number of synthetic pathways for various 4,7-disubstituted quinazoline derivatives displaying high therapeutic potential. However, no detailed characterization of this popular compound has been reported, possibly due to its high instability. In this paper, IV was prepared in an overall yield of 56.1% by a 3-step process (condensation, nitration, and chlorination) from 2-amino-4-chlorobenzoic acid (I). The target compound has been for the first time fully characterized by melting point, mass-spectrometry, FT-IR, 1H-NMR and 13C-NMR spectroscopies.

Insights into the EGFR SAR of N-phenylquinazolin-4-amine-derivatives using quantum mechanical pairwise-interaction energies

Protein kinases are an important class of enzymes that play an essential role in virtually all major disease areas. In addition, they account for approximately 50% of the current targets pursued in drug discovery research. In this work, we explore the generation of structure-based quantum mechanical (QM) quantitative structure-activity relationship models (QSAR) as a means to facilitate structure-guided optimization of protein kinase inhibitors. We explore whether more accurate, interpretable QSAR models can be generated for a series of 76 N-phenylquinazolin-4-amine inhibitors of epidermal growth factor receptor (EGFR) kinase by comparing and contrasting them to other standard QSAR methodologies. The QM-based method involved molecular docking of inhibitors followed by their QM optimization within a ~ 300 atom cluster model of the EGFR active site at the M062X/6-31G(d,p) level. Pairwise computations of the interaction energies with each active site residue were performed. QSAR models were generated by splitting the datasets 75:25 into a training and test set followed by modelling using partial least squares (PLS). Additional QSAR models were generated using alignment dependent CoMFA and CoMSIA methods as well as alignment independent physicochemical, e-state indices and fingerprint descriptors. The structure-based QM-QSAR model displayed good performance on the training and test sets (r² ~ 0.7) and was demonstrably more predictive than the QSAR models built using other methods. The descriptor coefficients from the QM-QSAR models allowed for a detailed rationalization of the active site SAR, which has implications for subsequent design iterations.

Synthesis and structure-activity relationship of nitrile-based cruzain inhibitors incorporating a trifluoroethylamine-based P2 amide replacement

The structure-activity relationship for nitrile-based cruzain inhibitors incorporating a P2 amide replacement based on trifluoroethylamine was explored by deconstruction of a published series of inhibitors. It was demonstrated that the P3 biphenyl substituent present in the published inhibitor structures could be truncated to phenyl with only a small loss of affinity. The effects of inverting the configuration of the P2 amide replacement and linking a benzyl substituent at P1 were observed to be strongly nonadditive. We show that plotting affinity against molecular size provides a means to visualize both the molecular size efficiency of structural transformations and the nonadditivity in the structure-activity relationship. We also show how the relationship between affinity and lipophilicity, measured by high-performance liquid chromatography with an immobilized artificial membrane stationary phase, may be used to normalize affinity with respect to lipophilicity.

Synthesis, antitumor testing and molecular modeling study of some new 6-substituted amido, azo or thioureido-quinazolin-4(3H)-ones

A new series of 6-substituted amido, azo or thioureido-quinazolin-4(3H)-one was synthesized and tested for their in-vitro antitumor activity. Compounds 21, 53 and 60 showed broad spectrum antitumor activity with average IC₅₀ values of 6.7, 7.6 and 9.1 μM, respectively compared with methotrexate (1, IC₅₀ 19.26 μM). As an attempt to reveal the mechanism of the antitumor potency, cell cycle analysis and DHFR inhibition were performed. Compounds 59 and 61 induced their cytotoxicity in Hela (IC₅₀ 10.6 μM) and HCT-116 (IC₅₀ 15.5 μM) cell lines, respectively through Pre-G1 apoptosis, inhibiting cell growth at G2-M phase. Compounds 29, 33, 59 and 61 showed DHFR inhibitory potency at IC₅₀ 0.2, 0.2, 0.3 and 0.3 μM, respectively. The active DHFR inhibitors showed high affinity binding toward the amino acid residues Thr56, Ser59 and Ser118. The active compounds obeyed Lipinski's rule of five and could be used as template model for further optimization.

The nature of ligand efficiency

Ligand efficiency is a widely used design parameter in drug discovery. It is calculated by scaling affinity by molecular size and has a nontrivial dependency on the concentration unit used to express affinity that stems from the inability of the logarithm function to take dimensioned arguments. Consequently, perception of efficiency varies with the choice of concentration unit and it is argued that the ligand efficiency metric is not physically meaningful nor should it be considered to be a metric. The dependence of ligand efficiency on the concentration unit can be eliminated by defining efficiency in terms of sensitivity of affinity to molecular size and this is illustrated with reference to fragment-to-lead optimizations. Group efficiency and fit quality are also examined in detail from a physicochemical perspective. The importance of examining relationships between affinity and molecular size directly is stressed throughout this study and an alternative to ligand efficiency for normalization of affinity with respect to molecular size is presented.

A novel scaffold for EGFR inhibition: Introducing N-(3-(3-phenylureido)quinoxalin-6-yl) acrylamide derivatives

Clinical data acquired over the last decade on non-small cell lung cancer (NSCLC) treatment with small molecular weight Epidermal Growth Factor Receptor (EGFR) inhibitors have shown significant influence of EGFR point mutations and in-frame deletions on clinical efficacy. Identification of small molecules capable of inhibiting the clinically relevant EGFR mutant forms is desirable, and novel chemical scaffolds might provide knowledge regarding selectivity among EGFR forms and shed light on new strategies to overcome current clinical limitations. Design, synthesis, docking studies and in vitro evaluation of N-(3-(3-phenylureido)quinoxalin-6-yl) acrylamide derivatives (7a-m) against EGFR mutant forms are described. Compounds 7h and 7l were biochemically active in the nanomolar range against EGFR_wt and EGFR_L858R. Molecular docking and reaction enthalpy calculations have shown the influence of the combination of reversible and covalent binding modes with EGFR on the inhibitory activity. The inhibitory profile of 7h against a panel of patient-derived tumor cell lines was established, demonstrating selective growth inhibition of EGFR related cells at 10 μM among a panel of 30 cell lines derived from colon, melanoma, breast, bladder, kidney, prostate, pancreas and ovary tumors.

Synthesis and Biological Evaluation of Some Novel Thiophene-bearing Quinazoline Derivatives as EGFR Inhibitors

Background:

With the approval of gefitinib, erlotinib, afatinib, and osimertinib for clinical use, targeting Epidermal Growth Factor Receptor (EGFR) has been intensively pursued. Similar to most therapies, challenges related to the treatment resistance against these drugs have emerged over time, so new EGFR Tyrosine Kinase Inhibitors (TKIs) need to be developed. This study aimed to investigate the potential use of a series of thiophene-bearing quinazoline derivatives as EGFR inhibitors. We designed and synthesized nine quinazolin derivatives, among which five compounds (5e, 5f, 5g, 5h, and 5i) were reported for the first time. </P><P> Methods: Two cancer cell lines, A431 (overexpressing EGFR) and A549 (EGFR wild-type and Kras mutation), were treated by these compounds and subjected to MTT assay. The A431 cells were selected for further treatment (5e) and Western blot analysis.

Results:

Although the compounds exerted no obvious effects on the proliferation of A549 cells, seven out of the nine compounds significantly inhibited the growth of A431 cells. In particular, the IC50 values of 5e and erlotinib were nearly equal. Western blot results showed that 5e significantly inhibited EGFR autophosphorylation in A431 cells. Structure-activity relationships indicated that quinazolines bearing 6,7-side chains were more potent than those unsubstituted at the 6,7-positions. Moreover, electron-withdrawing hydrophobic groups on the 5-position of the thiophene were preferred, such as chlorine or bromine atom.

Conclusion:

Nine 4-aminoquinazolin derivatives were designed, synthesized, and evaluated against A431 and A549 cell lines. Seven compounds significantly inhibited the growth of A431 cells. In particular, 5e possessed similar antitumor potency to that of erlotinib.

Novel series of 6-(2-substitutedacetamido)-4-anilinoquinazolines as EGFR-ERK signal transduction inhibitors in MCF-7 breast cancer cells

Epidermal growth factor receptor (EGFR) signaling pathway has been previously investigated for its significant role in the progression of different types of malignant tumors, where development of small molecules targeting EGFR is well known strategy for design of antitumor agents. Herein, we report the design and synthesis of two series of 6-(2-substitutedacetamido)-4-anilinoquinazolines (6a-x and 13a-d) as EGFR inhibitors. All the newly synthesized quinazoline derivatives were in vitro evaluated for their anti-proliferative activity towards MCF-7 (Breast Cancer) and HepG2 (Hepatocellular carcinoma) cell lines. In particular, compound 6n showed significant inhibitory activity against MCF-7 and HepG2 cell lines (IC₅₀ = 3 and 16 μM, respectively), compared to that of Erlotinib (IC₅₀ = 20 and 25 μM, respectively). Western blotting of 6n at MCF-7 cell line revealed the dual inhibitory activity of 6n towards diminishing the phosphorylated levels for EGFR and ERK. Also, ELISA assay confirmed the anti-EGFR activity of compound 6n (IC₅₀ = 0.037 μM). Finally, a molecular docking study showed the potential binding mode of 6n within the ATP catalytic binding site of EGFR, exhibiting similar binding mode to EGFR inhibitor Erlotinib.

Ligand-Based Pharmacophore Screening Strategy: a Pragmatic Approach for Targeting HER Proteins

Targeting ErbB family of receptors is an important therapeutic option, because of its essential role in the broad spectrum of human cancers, including non-small cell lung cancer (NSCLC). Therefore, in the present work, considerable effort has been made to develop an inhibitor against HER family proteins, by combining the use of pharmacophore modelling, docking scoring functions, and ADME property analysis. Initially, a five-point pharmacophore model was developed using known HER family inhibitors. The generated model was then used as a query to screen a total of 468,880 compounds of three databases namely ZINC, ASINEX, and DrugBank. Subsequently, docking analysis was carried out to obtain hit molecules that could inhibit the HER receptors. Further, analysis of GLIDE scores and ADME properties resulted in one hit namely BAS01025917 with higher glide scores, increased CNS involvement, and good pharmaceutically relevant properties than reference ligand, afatinib. Furthermore, the inhibitory activity of the lead compounds was validated by performing molecular dynamic simulations. Of note, BAS01025917 was found to possess scaffolds with a broad spectrum of antitumor activity. We believe that this novel hit molecule can be further exploited for the development of a pan-HER inhibitor with low toxicity and greater potential.

5-Azacytidine engages an IRE1α-EGFR-ERK1/2 signaling pathway that stabilizes the LDL receptor mRNA

Hepatic low-density lipoprotein receptor (LDLR) is the primary conduit for the clearance of plasma LDL-cholesterol and increasing its expression represents a central goal for treating cardiovascular disease. However, LDLR mRNA is unstable and undergoes rapid turnover mainly due to the three AU-rich elements (ARE) in its proximal 3'-untranslated region (3'-UTR). Herein, our data revealed that 5-azacytidine (5-AzaC), an antimetabolite used in the treatment of myelodysplastic syndrome, stabilizes the LDLR mRNA through a previously unrecognized signaling pathway resulting in a strong increase of its protein level in human hepatocytes in culture. 5-AzaC caused a sustained activation of the inositol-requiring enzyme 1α (IRE1α) kinase domain and c-Jun N-terminal kinase (JNK) independently of endoplasmic reticulum stress. This resulted in activation of the epidermal growth factor receptor (EGFR) and extracellular signal-regulated kinase1/2 (ERK1/2) that, in turn, stabilized LDLR mRNA. Systematic mutation of the AREs (ARE1-3) in the LDLR 3'UTR and expression of each mutant coupled to a luciferase reporter in Huh7 cells demonstrated that ARE1 is required for rapid LDLR mRNA decay and 5-AzaC-induced mRNA stabilization via the IRE1α-EGFR-ERK1/2 signaling cascade. The characterization of this pathway will help to reveal potential targets to enhance plasma LDL clearance and novel cholesterol-lowering therapeutic strategies.

Synthesis and In Vitro Cytotoxicity of the 4-(Halogenoanilino)-6-bromoquinazolines and Their 6-(4-Fluorophenyl) Substituted Derivatives as Potential Inhibitors of Epidermal Growth Factor Receptor Tyrosine Kinase

Series of the 2-unsubstituted and 2-(4-chlorophenyl)–substituted 4-anilino-6-bromoquinazolines and their 6-(4-fluorophenyl)–substituted derivatives were evaluated for in vitro cytotoxicity against MCF-7 and HeLa cells. The 2-unsubstituted 4-anilino-6-bromoquinazolines lacked activity, whereas most of their 2-(4-chlorophenyl) substituted derivatives were found to exhibit significant cytotoxicity and selectivity against HeLa cells. Replacement of bromine with 4-fluorophenyl group for the 2-unsubstituted 4-anilinoquinazolines resulted in superior activity against HeLa cells compared to Gefitinib. The presence of a 4-fluorophenyl group in the 2-(4-chlorophenyl) substituted derivatives led to increased cytotoxicity against HeLa cells, except for the 3-chloroanilino derivative. The most active compounds, namely, 3g, 3l, and 4l, were found to exhibit a moderate to significant inhibitory effect against epidermal growth factor receptor tyrosine kinase (EGFR-TK). The EGFR molecular docking model suggested that these compounds are nicely bound to the region of EGFR.

Novel 4-arylaminoquinazoline derivatives with (E)-propen-1-yl moiety as potent EGFR inhibitors with enhanced antiproliferative activities against tumor cells

A series of novel 4-anilinoquinazoline derivatives with (E)-propen-1-yl moiety were designed, synthesized and evaluated for biological activities in vitro. Most compounds exhibited highly antiproliferative activities against all tested tumor cell lines including A431, A549, NCI-H1975 and SW480 cells. Especially, compound 6e not only presented strong antiproliferative activities against the tested four tumor cell lines (IC₅₀ of 1.35, 8.83, 5.53 and 6.08 μM, respectively) which expressed wild type or L858R/T790M double mutant epidermal growth factor receptor (EGFR), but also showed potent inhibitory activity against wild type EGFR (IC₅₀ = 20.72 nM). The result of molecular docking with EGFR suggested the binding mode of 6e was similar to gefitinib, but different from lapatinib. Additionally, western blot analysis showed that 6e inhibited the phosphorylation of EGFR and its downstream signaling proteins in lung cancer cells. The work could be very useful starting point for developing a new series of tyrosine kinase inhibitors targeting EGFR.

2D-QSAR and 3D-QSAR Analyses for EGFR Inhibitors

Epidermal growth factor receptor (EGFR) is an important target for cancer therapy. In this study, EGFR inhibitors were investigated to build a two-dimensional quantitative structure-activity relationship (2D-QSAR) model and a three-dimensional quantitative structure-activity relationship (3D-QSAR) model. In the 2D-QSAR model, the support vector machine (SVM) classifier combined with the feature selection method was applied to predict whether a compound was an EGFR inhibitor. As a result, the prediction accuracy of the 2D-QSAR model was 98.99% by using tenfold cross-validation test and 97.67% by using independent set test. Then, in the 3D-QSAR model, the model with q² = 0.565 (cross-validated correlation coefficient) and r² = 0.888 (non-cross-validated correlation coefficient) was built to predict the activity of EGFR inhibitors. The mean absolute error (MAE) of the training set and test set was 0.308 log units and 0.526 log units, respectively. In addition, molecular docking was also employed to investigate the interaction between EGFR inhibitors and EGFR.

18F-Labeled Pyrido[3,4-d]pyrimidine as an Effective Probe for Imaging of L858R Mutant Epidermal Growth Factor Receptor

In nonsmall-cell lung carcinoma patients, L858R mutation of epidermal growth factor receptor (EGFR) is often found, and molecular target therapy using EGFR tyrosine kinase inhibitors is effective for the patients. However, the treatment frequently develops drug resistance by secondary mutation, of which approximately 50% is T790M mutation. Therefore, the ability to predict whether EGFR will undergo secondary mutation is extremely important. We synthesized a novel radiofluorinated 4-(anilino)pyrido[3,4-d]pyrimidine derivative ([¹⁸F]APP-1) and evaluated its potential as a positron emission tomography (PET) imaging probe to discriminate the difference in mutations of tumors. EGFR inhibition assay, cell uptake, and biodistribution study showed that [¹⁸F]APP-1 binds specifically to the L858R mutant EGFR but not to the L858R/T790M mutant. Finally, on PET imaging study using [¹⁸F]APP-1 with tumor-bearing mice, the H3255 tumor (L858R mutant) was more clearly visualized than the H1975 tumor (L858R/T790M mutant).

Synthesis of novel 1,2,4-triazole derivatives containing the quinazolinylpiperidinyl moiety and N-(substituted phenyl)acetamide group as efficient bactericides against the phytopathogenic bacterium Xanthomonas oryzae pv. oryzae

Some 1,2,4-triazole derivatives containing the quinazolinylpiperidinyl moiety andN-(substituted phenyl)acetamide group were developed as efficient bactericides against pathogenic bacteriumXoo.

Covalent EGFR Inhibitors: Binding Mechanisms, Synthetic Approaches, and Clinical Profiles

Being overexpressed in several types of cancer, the epidermal growth factor receptor (EGFR) is considered one of the key therapeutic targets in oncology. Although many first-generation EGFR inhibitors had been FDA approved for the treatment of certain types of cancer, patients soon developed resistance to these reversible ATP competitive inhibitors via mutations in the kinase domain of EGFR. A new trend was adopted to design covalent irreversible inhibitors, that is, second- and third-generation inhibitors. Second-generation inhibitors can inhibit the mutant forms but, unfortunately, they had dose limiting side effects due to wild-type EGFR inhibition. Third-generation inhibitors emerged shortly, which were capable of inhibiting the mutant forms exclusively while sparing the wild type. Many other strategies have also been developed to reduce the risk of covalent interactions with off-targets, thus improving the pharmacokinetic and/or pharmacodynamic profile of the antiproliferative agents. In this review, we focused mainly on second- and third-generation EGFR inhibitors, their binding mechanisms (either docking studies or co-crystallized structures), their synthetic approaches, clinical profiles, and limitations.

Optimization of a Novel Series of Ataxia-Telangiectasia Mutated Kinase Inhibitors as Potential Radiosensitizing Agents

We previously reported a novel inhibitor of the ataxia-telangiectasia mutated (ATM) kinase, which is a target for novel radiosensitizing drugs. While our initial lead, compound 4, was relatively potent and nontoxic, it exhibited poor stability to oxidative metabolism and relatively poor selectivity against other kinases. The current study focused on balancing potency and selectivity with metabolic stability through structural modification to the metabolized site on the quinazoline core. We performed extensive structure-activity and structure-property relationship studies on this quinazoline ATM kinase inhibitor in order to identify structural variants with enhanced selectivity and metabolic stability. We show that, while the C-7-methoxy group is essential for potency, replacing the C-6-methoxy group considerably improves metabolic stability without affecting potency. Promising analogues 20, 27g, and 27n were selected based on in vitro pharmacology and evaluated in murine pharmacokinetic and tolerability studies. Compound 27g possessed significantly improve pharmacokinetics relative to that of 4. Compound 27g was also significantly more selective against other kinases than 4. Therefore, 27g is a good candidate for further development as a potential radiosensitizer.

Access to enhanced catalytic core–shell CuO–Pd nanoparticles for the organic transformations

This paper describes the biosynthesis of core–shell CuO–Pd nanocatalysts with the aid of a Cyperus rotundus rhizome extract.

Homogeneous single-label tyrosine kinase activity assay for high throughput screening

Protein post-translational modifications (PTMs) are regulatory mechanisms carried out by different enzymes in a cell. Kinase catalyzed phosphorylation is one of the most important PTM affecting the protein activity and function. We have developed a single-label quenching resonance energy transfer (QRET) assay to monitor tyrosine phosphorylation in a homogeneous high throughput compatible format. Epidermal growth factor receptor (EGFR) induced phosphorylation was monitored using Eu(3+)-chelate labeled peptide and label-free phosphotyrosine specific antibody in presence of a soluble quencher molecule. In the QRET kinase assay, antibody binding to phosphorylated Eu(3+)-peptide protects the Eu(3+)-chelate from luminescence quenching, monitoring high time-resolved luminescence (TRL) signals. In the presence of specific kinase inhibitor, antibody recognition and Eu(3+)-chelate protection is prevented, allowing an efficient luminescence quenching. The assay functionality was demonstrated with a panel of EGFR inhibitors (AG-1478, compound 56, erlotinib, PD174265, and staurosporine). The monitored IC50 values ranged from 0.08 to 155.3 nM and were comparable to those found in the literature. EGFR activity and inhibition assays were performed using low nanomolar enzyme and antibody concentration in a 384-well plate format, demonstrating its compatibility for high throughput screening (HTS).

Cytotoxicity of the Urokinase-Plasminogen Activator Inhibitor Carbamimidothioic Acid (4-Boronophenyl) Methyl Ester Hydrobromide (BC-11) on Triple-Negative MDA-MB231 Breast Cancer Cells

BC-11 is an easily synthesized simple thiouronium-substituted phenylboronic acid, which has been shown to be cytotoxic on triple negative MDA-MB231 breast cancer cells by inducing a perturbation of cell cycle when administered at a concentration equal to its ED₅₀ at 72 h (117 μM). Exposure of cells to BC-11, either pre-absorbed with a soluble preparation of the N-terminal fragment of urokinase-plasminogen activator (uPa), or in co-treatment with two different EGFR inhibitors, indicated that: (i) BC-11 acts via binding to the N-terminus of the enzyme where uPa- and EGF receptor-recognizing sites are present, thereby abrogating the growth-sustaining effect resulting from receptor binding; and (ii) the co-presence of the EGFR inhibitor PD153035 potentiates BC-11’s cytotoxicity. Exposure of cells to a higher concentration of BC-11 corresponding to its ED₇₅ at 72 h (250 μM) caused additional impairment of mitochondrial activity, the production of reactive oxygen species and promotion of apoptosis. Therefore, BC-11 treatment appears to show potential for the development of this class of compounds in the prevention and/or therapy of “aggressive” breast carcinoma.

Fighting cancer drug resistance: Opportunities and challenges for mutation-specific EGFR inhibitors

Multiple mutations in the EGFR gene are a major cause for the failure of Erlotinib and Gefitinib in the treatment of patients harboring non-small-cell lung cancer (NSCLC) who initially responded to this therapy. The development of these tyrosine kinase inhibitors (TKIs) is going back to the early 90s, where cancer was widely considered and fully treated as a disease of an organ. Fundamental gain of knowledge in cell biology in general and cancer genetics in particular led us to where we currently stand: cancer is a disease that originates in the genome. Fast and affordable gene sequencing paved the way and opened our eyes for the genetic instability of many cancers, particularly EGFR driven NSCLC. This might allow highly rational and personal therapies by aiming at a very particular wild type and mutant kinase pattern. However, the paradigm "one disease - one target - one drug" is currently challenged. Both activating and deactivating EGFR mutations are known to render the development of novel targeted drugs difficult. Among all lung adenocarcinomas, only 20% are driven by EGFR and only a subpopulation has an activating mutation (e.g. L858R), making them sensitive to first generation EGFR inhibitors. Unfortunately, most of them acquire second deactivating mutations (e.g. T790M) during treatment, leading to a complete loss of response. Are specific inhibitors of the double EGFR mutant L858R/T790M the magic bullet? Much scientific evidence but also high expectations justify this approach. Structural biology of EGFR mutants constitutes the basis for highly rational approaches. Second generation pan EGFR inhibitors inhibiting wild type (WT) and mutant EGFR like Afatinib suffer from dose-limiting adverse effects. Inhibition of WT EGFR is considered to be the culprit. Third generation EGFR inhibitors follow two strategies. Mutant selectivity and improved target residential time. These inhibitors display high mutant selectivity and irreversible binding patterns while sparing WT EGFR activity, hence enhancing tumor selectivity while minimizing adverse effects. Third generation EGFR inhibitors are still undergoing preclinical and clinical evaluation. The most advanced are Rociletinib and AZD9291 which displayed encouraging preliminary clinical phase II data regarding response and adverse effects. In the current review we show both a medicinal chemists' approach toward the design of third generation EGFR inhibitors as well as a detailed overview of the development of EGFR inhibitors over the last decade. High interdisciplinary approaches, such as structural biology and time-resolved tumor genetics pave the way toward the development of drugs that target EGFR mutants. This might lead to highly effective targeted and personalized therapies with enhanced response rates for a minor cohort of patients which have to undergo continuous gene sequencing, hence enabling therapies with tailor-made TKIs.

Rational design of inhibitors of the bacterial cell wall synthetic enzyme GlmU using virtual screening and lead-hopping

An aminoquinazoline series targeting the essential bacterial enzyme GlmU (uridyltransferase) were previously reported (Biochem. J.2012, 446, 405). In this study, we further explored SAR through a combination of traditional medicinal chemistry and structure-based drug design, resulting in a novel scaffold (benzamide) with selectivity against protein kinases. Virtual screening identified fragments that could be fused into the core scaffold, exploiting additional binding interactions and thus improving potency. These efforts resulted in a hybrid compound with target potency increased by a 1000-fold, while maintaining selectivity against selected protein kinases and an improved level of solubility and protein binding. Despite these significant improvements no significant antibacterial activity was yet observed within this class.

Emission tuning of fluorescent kinase inhibitors: conjugation length and substituent effects

Fluorescent N-phenyl-4-aminoquinazoline probes targeting the ATP-binding pocket of the ERBB family of receptor tyrosine kinases are reported. Extension of the aromatic quinazoline core with fluorophore “arms” through substitution at the 6- position of the quinazoline core with phenyl, styryl, and phenylbutadienyl moieties was predicted by means of TD-DFT calculations to produce probes with tunable photoexcitation energies and excited states possessing charge-transfer character. Optical spectroscopy identified several synthesized probes that are nonemissive in aqueous solutions and exhibit emission enhancements in solvents of low polarity, suggesting good performance as turn-on fluorophores. Ligand-induced ERBB2 phosphorylation assays demonstrate that despite chemical modification to the quinazoline core these probes still function as ERBB2 inhibitors in MCF7 cells. Two probes were found to exhibit ERBB2-induced fluorescence, demonstrating the utility of these probes as turn-on, fluoroescent kinase inhibitors.

Identification and optimization of indolo[2,3-c]quinoline inhibitors of IRAK4

IRAK4 is responsible for initiating signaling from Toll-like receptors (TLRs) and members of the IL-1/18 receptor family. Kinase-inactive knock-ins and targeted deletions of IRAK4 in mice cause reductions in TLR induced pro-inflammatory cytokines and these mice are resistant to various models of arthritis. Herein we report the identification and optimization of a series of potent IRAK4 inhibitors. Representative examples from this series showed excellent selectivity over a panel of kinases, including the kinases known to play a role in TLR-mediated signaling. The compounds exhibited low nM potency in LPS- and R848-induced cytokine assays indicating that they are blocking the TLR signaling pathway. A key compound (26) from this series was profiled in more detail and found to have an excellent pharmaceutical profile as measured by predictive assays such as microsomal stability, TPSA, solubility, and clogP. However, this compound was found to afford poor exposure in mouse upon IP or IV administration. We found that removal of the ionizable solubilizing group (32) led to increased exposure, presumably due to increased permeability. Compounds 26 and 32, when dosed to plasma levels corresponding to ex vivo whole blood potency, were shown to inhibit LPS-induced TNFα in an in vivo murine model. To our knowledge, this is the first published in vivo demonstration that inhibition of the IRAK4 pathway by a small molecule can recapitulate the phenotype of IRAK4 knockout mice.