Dianilinophthalimides: potent and selective, ATP-competitive inhibitors of the EGF-receptor protein tyrosine kinase

The Genus Chrysosporium: A Potential Producer of Natural Products

Chrysosporium, a genus of ascomycete fungi in the family Onygenaceae, has the ability to produce abundant new bioactive natural products, providing a structural foundation in drug development. This review includes the sources, distribution, biological activities and structural characteristics of the compounds isolated from Chrysosporium from 1984 to 2021. The results show that 66% of the compounds isolated from Chrysosporium are new natural products. More than half of the Chrysosporium-isolated compounds are from marine-derived Chrysosporium. The chemical structures of Chrysosporium-derived compounds have different skeletons, which are concentrated in alkaloids, polyketides, and lactones. Eighty percent of the natural products isolated from Chrysosporium have been found to have various biological activities, including cytotoxic, antibacterial, antifungal and enzyme-inhibitory activities. These results demonstrate the potential of Chrysosporium for producing new bioactive secondary metabolites, which can be used as the structural basis for developing new drugs.

Specific signature biomarkers highlight the potential mechanisms of circulating neutrophils in aneurysmal subarachnoid hemorrhage

Background: Aneurysmal subarachnoid hemorrhage (aSAH) is a devastating hemorrhagic stroke with high disability and mortality. Neuroinflammation and the immunological response after aSAH are complex pathophysiological processes that have not yet been fully elucidated. Therefore, attention should be paid to exploring the inflammation-related genes involved in the systemic response to the rupture of intracranial aneurysms.

Methods: The datasets of gene transcriptomes were downloaded from the Gene Expression Omnibus database. We constructed a gene co-expression network to identify cluster genes associated with aSAH and screened out differentially expressed genes (DEGs). The common gene was subsequently applied to identify hub genes by protein-protein interaction analysis and screen signature genes by machine learning algorithms. CMap analysis was implemented to identify potential small-molecule compounds. Meanwhile, Cibersort and ssGSEA were used to evaluate the immune cell composition, and GSEA reveals signal biological pathways.

Results: We identified 602 DEGs from the GSE36791. The neutrophil-related module associated with aSAH was screened by weighted gene co-expression network analysis (WGCNA) and functional enrichment analysis. Several small molecular compounds were predicted based on neutrophil-related genes. MAPK14, ITGAM, TLR4, and FCGR1A have been identified as crucial genes involved in the peripheral immune activation related to neutrophils. Six significant genes (CST7, HSP90AB1, PADI4, PLBD1, RAB32, and SLAMF6) were identified as signature biomarkers by performing the LASSO analysis and SVM algorithms. The constructed machine learning model appears to be robust by receiver-operating characteristic curve analysis. The immune feature analysis demonstrated that neutrophils were upregulated post-aSAH and PADI4 was positively correlated with neutrophils. The NETs pathway was significantly upregulated in aSAH.

Conclusion: We identified core regulatory genes influencing the transcription profiles of circulating neutrophils after the rupture of intracranial aneurysms using bioinformatics analysis and machine learning algorithms. This study provides new insight into the mechanism of peripheral immune response and inflammation after aSAH.

Design and synthesis of novel pyrrolo[2,3-a]carbazoles: 7-Chloro-2-oxo-3a-(2'-oxo-2',3'-dihydro-1'H-indol-3'-yl)-2,3,3a,4,5,10-hexahydro-pyrrolo[3,2-a]carbazole-1-carbonitrile as an efficient anticancer agent

Highly efficient poly functionalized pyrrolo[3,2-a]carbazoles via ring contraction through rearrangement and intramolecular Michael addition reaction using one pot multicomponent reaction (MCR) is reported for the first time. Free radical scavenging and anticancer activities were determined by DPPH and MTT assays respectively. Of these, compound 8d exhibited most potent activity against HCT-15 human colon cancer cell lines with an IC₅₀ value of 9.9 μM and low toxicity toward normal human red blood cells. The morphological changes were visualized using scanning electron microscopy (SEM) technique, intracellular ROS generation measured by spectrofluorometer and gene expression levels of caspase-3, caspase-9 and Bcl-2 were determined using Semi quantitates PCR analysis for the target compound. Further, the structure activity relationships were also carried out. The results of the present study revealed that among pyrrolo[3,2-a]carbazole compounds, 7-chloro-2-oxo-3a-(2'-oxo-2',3'-dihydro-1'H-indol-3'-yl)-2,3,3a,4,5,10-hexahydro-pyrrolo[3,2-a]carbazole-1-carbonitrile could be exploited as an excellent anticancer agent against colon cancer cells.

Design and synthesis of a series of novel bisquinazoline glycosides as epidermal growth factor receptor inhibitors

A new series of potential epidermal growth factor receptor inhibitors possessing bisquinazoline and saccharide moieties were designed and synthesized. The biological results demonstrated that the synthetic derivatives significantly inhibited epidermal growth factor receptor enzymatic activity in vitro. Of them, compound 14b showed the highest inhibitory rate toward epidermal growth factor receptor protein tyrosine kinase (81.36%) at a concentration of 1 μM. Further molecular simulation predicted that 14b offered its saccharide moieties hydrogen bonding to ATP-binding pocket.

A synergistic small-molecule combination directly eradicates diverse prion strain structures

Safely eradicating prions, amyloids and preamyloid oligomers may ameliorate several fatal neurodegenerative disorders. Yet, whether small-molecule drugs can directly antagonize the entire spectrum of distinct amyloid structures or ‘strains’ that underlie distinct disease states is unclear. Here, we investigated this issue using the yeast prion protein Sup35. We have established how epigallocatechin-3-gallate (EGCG) blocks synthetic Sup35 prionogenesis, eliminates preformed Sup35 prions, and disrupts inter- and intra-molecular prion contacts. Unexpectedly, these direct activities were strain selective, altered the repertoire of accessible infectious forms and facilitated emergence of a new prion strain that configured original, EGCG-resistant intermolecular contacts. In vivo, EGCG cured and prevented induction of susceptible but not resistant strains, and elicited switching from susceptible to resistant forms. Importantly, 4,5-bis-(4-methoxyanilino)phthalimide directly antagonized EGCG-resistant prions and synergized with EGCG to eliminate diverse Sup35 prion strains. Thus, synergistic small-molecule combinations that directly eradicate complete strain repertoires likely hold considerable therapeutic potential.

Direct and selective elimination of specific prions and amyloids by 4,5-dianilinophthalimide and analogs

Mechanisms to safely eliminate amyloids and preamyloid oligomers associated with many devastating diseases are urgently needed. Biophysical principles dictate that small molecules are unlikely to perturb large intermolecular protein-protein interfaces, let alone extraordinarily stable amyloid interfaces. Yet 4,5-dianilinophthalimide (DAPH-1) reverses Abeta42 amyloidogenesis and neurotoxicity, which is associated with Alzheimer's disease. Here, we show that DAPH-1 and select derivatives are ineffective against several amyloidogenic proteins, including tau, alpha-synuclein, Ure2, and PrP, but antagonize the yeast prion protein, Sup35, in vitro and in vivo. This allowed us to exploit several powerful new tools created for studying the conformational transitions of Sup35 and decipher the mechanisms by which DAPH-1 and related compounds antagonize the prion state. During fibrillization, inhibitory DAPHs alter the folding of Sup35's amyloidogenic core, preventing amyloidogenic oligomerization and specific recognition events that nucleate prion assembly. Select DAPHs also are capable of attacking preformed amyloids. They remodel Sup35 prion-specific intermolecular interfaces to create morphologically altered aggregates with diminished infectivity and self-templating activity. Our studies provide mechanistic insights and reinvigorate hopes for small-molecule therapies that specifically disrupt intermolecular amyloid contacts.

Gefitinib induces myeloid differentiation of acute myeloid leukemia

Cure rates for patients with acute myeloid leukemia (AML) remain low despite ever-increasing dose intensity of cytotoxic therapy. In an effort to identify novel approaches to AML therapy, we recently reported a new method of chemical screening based on the modulation of a gene expression signature of interest. We applied this approach to the discovery of AML-differentiation-promoting compounds. Among the compounds inducing neutrophilic differentiation was DAPH1 (4,5-dianilinophthalimide), previously reported to inhibit epidermal growth factor receptor (EGFR) kinase activity. Here we report that the Food and Drug Administration (FDA)-approved EGFR inhibitor gefitinib similarly promotes the differentiation of AML cell lines and primary patient-derived AML blasts in vitro. Gefitinib induced differentiation based on morphologic assessment, nitro-blue tetrazolium reduction, cell-surface markers, genome-wide patterns of gene expression, and inhibition of proliferation at clinically achievable doses. Importantly, EGFR expression was not detected in AML cells, indicating that gefitinib functions through a previously unrecognized EGFR-independent mechanism. These studies indicate that clinical trials testing the efficacy of gefitinib in patients with AML are warranted.

MetaSite: Understanding Metabolism in Human Cytochromes from the Perspective of the Chemist

Identification of metabolic biotransformations can significantly affect the drug discovery process. Since bioavailability, activity, toxicity, distribution, and final elimination all depend on metabolic biotransformations, it would be extremely advantageous if this information could be produced early in the discovery phase. Once obtained, this information can help chemists to judge whether a potential candidate should be eliminated from the pipeline or modified to improve chemical stability or safety of new compounds. The use of in silico methods to predict the site of metabolism in phase I cytochrome-mediated reactions is a starting point in any metabolic pathway prediction. This paper presents a new method, specifically designed for chemists, that provides the cytochrome involved and the site of metabolism for any human cytochrome P450 (CYP) mediated reaction acting on new substrates. The methodology can be applied automatically to all the cytochromes for which 3D structure is known and can be used by chemists to detect positions that should be protected in order to avoid metabolic degradation or to check the suitability of a new scaffold or prodrug. The fully automated procedure is also a valuable new tool in early ADME-Tox assays (absorption, distribution, metabolism, and excretion toxicity assays), where drug safety and metabolic profile patterns must be evaluated as soon, and as early, as possible.

Synthesis of 4,5-Dianilinophthalimide and Related Analogues for Potential Treatment of Alzheimer's Disease via Palladium-Catalyzed Amination

DAPH (4,5-dianilinophthalimide) has previously been shown to reverse the formation of neurotoxic fibrils associated with Alzheimer's disease. We have developed a synthetic route to DAPH and structurally related analogues that employs palladium-catalyzed amination as the key bond-forming step. The requisite substrates are easily obtained, and their coupling with substituted anilines proceeds in generally high yields. Thus, a variety of DAPH analogues can be quickly accessed in a modular fashion. In addition, the route described herein should also be amenable to the incorporation of other classes of nucleophiles into the molecular framework.

Secondary metabolites of slime molds (myxomycetes)

The compounds reported from the slime molds (myxomycetes) species are described. Almost 100 natural compounds including their chemical structures and biological activities are described in this review article. Only metabolites with a well-defined structure are included.

Synthesis and SAR of potent EGFR/erbB2 dual inhibitors

A series of 6-alkoxy-4-anilinoquinazoline compounds was prepared and evaluated for in vitro inhibition of the erbB2 and EGFR kinase activity. The IC(50) values of the best compounds were below 0.10 uM. Further, several of these compounds inhibit the growth of erbB2 and EGFR over-expressing tumor cell lines at concentrations below 1 uM.

Synthesis of aryl- and heteroaryl[a]pyrrolo[3,4-c]carbazoles

Synthesis of aryl- and hetero[a]pyrrolo[3,4-c]carbazoles by photochemical oxidation and Heck cyclization are described. Photochemical oxidation of 2-naphthyl indolyl maleimide affords two different carbazole regioisomers, depending on the reaction conditions. The regiochemistry of the cyclization can be controlled using the Heck reaction.

Angiotensin II triggers EGFR tyrosine kinase-dependent Ca2+ influx in afferent arterioles

We previously reported that inhibition of epidermal growth factor receptor tyrosine kinase activity attenuates renal arteriolar contractile responses to angiotensin II. We performed the present experiments to determine if epidermal growth factor receptor tyrosine kinase activity contributes to the afferent arteriolar intracellular [Ca2+] response to angiotensin II. Afferent arterioles were dissected from rat kidney and intracellular [Ca2+] was monitored with the use of fura-2. In normal Ringer's bath containing 1.5 mmol/L Ca2+, basal intracellular [Ca2+] averaged 95+/-7 nmol/L and 100 nmol/L angiotensin II caused a rapid rise (peak Delta=75+/-10 nmol/L) that waned to a plateau averaging 24+/-5 nmol/L above baseline. Pretreatment with 100 nmol/L AG1478 (epidermal growth factor receptor tyrosine kinase inhibitor) reduced both the peak and the plateau stages of the angiotensin II response (peak Delta=42+/-7 nmol/L; plateau Delta=8+/-4 nmol/L). A structurally unrelated epidermal growth factor receptor tyrosine kinase inhibitor also suppressed the peak response to angiotensin II, whereas tyrosine phosphatase inhibition enhanced the plateau phase of the response. In the presence of 100 nmol/L extracellular Ca2+, the angiotensin II response was characterized by a peak of diminished magnitude (Delta=49+/-10 nmol/L; P<0.05 versus the response in normal Ringer's bath) with no plateau, and this response was unaffected by AG1478. Moreover, angiotensin II stimulation of divalent cation influx (Mn2+ quench of fura-2 fluorescence) was decreased significantly by AG1478. We conclude that epidermal growth factor receptor tyrosine kinase activity contributes to the afferent arteriolar intracellular [Ca2+] response to angiotensin II and that this process involves promotion of Ca2+ influx.

Tyrosine kinases as targets for cancer therapy

Enhanced protein tyrosine kinase (PTK) activity correlates with the development of cancer and other proliferative diseases. The hypothesis that PTK inhibitors may be of value in the treatment of cancer led to the systematic synthesis of selective tyrosine phosphorylation inhibitors (tyrphostins) that show in vitro and in vivo anticancer activity. This review will provide an overview of research efforts in the development of tyrphostins such as AG 957, AG 1112, and AG 1318. Other tyrphostins discussed are AG 1478 and RG 13022, which are both epidermal growth factor receptor kinase inhibitors; AG 490, a Jak-2 kinase inhibitor; AG 1296, a PDGFR kinase inhibitor; and STI 571 (imatinib, Glivec/Gleevec; Novartis Pharma AG, Basel, Switzerland). STI 571 is now approved for the treatment of chronic myeloid leukemia and shows activity against gastrointestinal stromal tumors. The chemistry, kinetics, biological activity, and clinical potential of these compounds will be discussed.

Inhibiting signal transduction: recent advances in the development of receptor tyrosine kinase and Ras inhibitors

Since aberrant cell signaling is implicated in the initiation, growth, and progression of cancer, proteins involved in signal transduction are rational therapeutic targets. Receptor tyrosine kinases (RTK) and Ras oncoprotein are examples of critical signaling proteins that mediate the processes of cellular growth and differentiation. Agents presently being evaluated as inhibitors of signal transduction include both natural and synthetic compounds, monoclonal antibodies, and antisense oligonucleotides. Preclinical studies of compounds which inhibit RTK and Ras have shown that these targets can be blocked, while side effects in animal models are minimal. Early clinical trials reveal that, in general, treatment with these compounds is both feasible and tolerable. However, many issues about STI remain unresolved including how to optimize schedule, how long to continue treatment, specific mechanisms of action, and how to optimize combinations of STI with standard therapeutic modalities. Addressing these issues may require a shift in the traditional paradigm of drug development, as conventional endpoints may not adequately capture the potential benefits from agents believed to act in a cytostatic vs. cytotoxic manner. This review will discuss the rationale and application of inhibiting signal transduction using inhibitors of RTK and Ras as prototypes of this class of agents.

Structure-based design and synthesis of 2-benzylidene-benzofuran-3-ones as flavopiridol mimics

Novel 2-benzylidene-benzofuran-3-ones were designed and synthesized to mimic flavopiridol, a well-established inhibitor of cyclin-dependent kinases (CDKs) which is currently undergoing clinical evaluation. The underlying design concepts as well as the synthesis and structure-activity relationships (CDKs 1, 2, and 4 enzyme assays) of these mimics are described. Inhibitors of CDKs 1 and 2 that are more potent and selective than flavopiridol were obtained.

Computational analysis of PKA-balanol interactions

Protein kinases are important targets for designing therapeutic drugs. This paper illustrates a computational approach to extend the usefulness of a single protein-inhibitor structure in aiding the design of protein kinase inhibitors. Using the complex structure of the catalytic subunit of PKA (cPKA) and balanol as a guide, we have analyzed and compared the distribution of amino acid types near the protein-ligand interface for nearly 400 kinases. This analysis has identified a number of sites that are more variable in amino acid types among the kinases analyzed, and these are useful sites to consider in designing specific protein kinase inhibitors. On the other hand, we have found kinases whose protein-ligand interfaces are similar to that of the cPKA-balanol complex and balanol can be a useful lead compound for developing effective inhibitors for these kinases. Generally, this approach can help us discover new drug targets for an existing class of compounds that have already been well characterized pharmacologically. The relative significance of the charge/polarity of residues at the protein-ligand interface has been quantified by carrying out computational sensitivity analysis in which the charge/polarity of an atom or functional group was turned off/on, and the resulting effects on binding affinity have been examined. The binding affinity was estimated by using an implicit-solvent model in which the electrostatic contributions were obtained by solving the Poisson equation and the hydrophobic effects were accounted for by using surface-area dependent terms. The same sensitivity analysis approach was applied to the ligand balanol to develop a pharmacophoric model for searching new drug leads from small-molecule libraries. To help evaluate the binding affinity of designed inhibitors before they are made, we have developed a semiempirical approach to improve the predictive reliability of the implicit-solvent binding model.

Inhibition of tumor angiogenesis by synthetic receptor tyrosine kinase inhibitors

Protein tyrosine kinases have emerged as crucial targets for therapeutic intervention in cancer. More recently, growth factor ligands and their respective receptor tyrosine kinases (RTKs) have been shown to be required for tumor cell growth. This latter aspect includes tumor angiogenesis where the growth of tumors leads to compensatory effects on host cells in the tumor microenvironment leading to the growth of microvessels. The purpose of this review is to focus on synthetic chemical approaches to block RTKs associated with tumor angiogenesis as a means to limit the growth and spread of human tumors.

Protein tyrosine kinases: structure, substrate specificity, and drug discovery

Protein tyrosine kinases (PTKs) play a crucial role in many cell regulatory processes. It is therefore not surprising to see that functional perturbation of PTKs results in many diseases. Despite the diverse primary structure organization of various PTKs, the catalytic or kinase domains of various PTKs as well as that of Ser/Thr kinases are generally conserved. The high resolution crystal structure of a few PTKs has been solved in the last few years. In contrast to the well-defined linear peptide substrate motifs recognized by specific Ser/Thr kinases, the identification of specific substrate motifs for PTK has been slow. It is not until recently that through the use of combinatorial peptide library methods that specific recognition motifs for specific PTKs have begun to emerge. Efficient and specific peptide substrates for some PTKs with Km at the mid microM range have been identified. Based on these peptide substrates, relatively potent (IC50 at the low microM range) and highly selective pseudosubstrate-based peptide inhibitors have been developed. There has been enormous effort in the development of PTK inhibitors for diseases such as cancer, psoriasis, and osteoporosis. Several new high-throughput PTK assay technologies have recently been described. Small molecules against specific PTK have been developed. Most of them are competitive inhibitors at the ATP binding site. Some of these inhibitors have already been in clinical trial.

Clavilactones, a novel class of tyrosine kinase inhibitors of fungal origin

Targeting of deregulated protein tyrosine kinases has been proposed as a new approach in the therapeutic intervention against pathological processes including proliferative disorders and cancer. Using a screening approach based on a comparative evaluation of antiproliferative effects in a panel of tumor cells with differential expression of protein tyrosine kinases, three benzoquinoid macrolidic fungal metabolites produced by Clitocybe clavipes, clavilactones A, B, and D (CA, CB, and CD) and two semisynthetic derivatives of these products, diacetyl-CA and dimethyl-CA, were identified as inhibitors of protein tyrosine kinases. Naturally occurring CA, CB, and CD showed inhibitory activity in kinase assays against the Ret/ptc1 and epidermal growth factor receptor (EGF-R) tyrosine kinases, while being less effective against the v-Abl tyrosine kinase and p34(cdc2) serine/threonine kinase (IC(50) 2.8, 5.5, 81.3, and 128 microM respectively, for the most potent compound CD). CB was shown to be a non-competitive inhibitor of EGF-R with respect to ATP or poly(Glu(6)Ala(3)Tyr). CD also preferentially inhibited the growth of A431 cells, which overexpress a constitutively active EGF-R, as opposed to IGROV-1 and SKOV-3 cells, which express low levels of the receptor. Further, EGF-R was shown to be a target for clavilactones in A431 cells, since EGF-induced receptor autophosphorylation was inhibited in the presence of CB, CD, and diacetyl-CA. Both CD and diacetyl-CA displayed weak activity when administered daily (i.p.) to mice bearing ascitic A431 tumor. These findings indicate that clavilactones represent the prototypes of a new structural class of tyrosine kinase inhibitors deserving further investigation.

New anilinophthalazines as potent and orally well absorbed inhibitors of the VEGF receptor tyrosine kinases useful as antagonists of tumor-driven angiogenesis

The sprouting of new blood vessels, or angiogenesis, is necessary for any solid tumor to grow large enough to cause life-threatening disease. Vascular endothelial growth factor (VEGF) is one of the key promoters of tumor induced angiogenesis. VEGF receptors, the tyrosine kinases Flt-1 and KDR, are expressed on vascular endothelial cells and initiate angiogenesis upon activation by VEGF. 1-Anilino-(4-pyridylmethyl)-phthalazines, such as CGP 79787D (or PTK787 / ZK222584), reversibly inhibit Flt-1 and KDR with IC(50) values < 0.1 microM. CGP 79787D also blocks the VEGF-induced receptor autophosphorylation in CHO cells ectopically expressing the KDR receptor (ED(50) = 34 nM). Modification of the 1-anilino moiety afforded derivatives with higher selectivity for the VEGF receptor tyrosine kinases Flt-1 and KDR compared to the related receptor tyrosine kinases PDGF-R and c-Kit. Since these 1-anilino-(4-pyridylmethyl)phthalazines are orally well absorbed, these compounds qualify for further profiling and as candidates for clinical evaluation.

Substituted 5,7-diphenyl-pyrrolo[2,3d]pyrimidines: potent inhibitors of the tyrosine kinase c-Src

5,7-Diphenyl-pyrrolo[2,3d]pyrimidines represent a new class of highly potent inhibitors of the tyrosine kinase c-Src (IC50 < 50 nM) with specificity against a panel of different tyrosine kinases. The substitution pattern on the two phenyl rings determines potency and specificity and provides a means to modulate cellular activity.

Tyrosine kinase inhibitors. 17. Irreversible inhibitors of the epidermal growth factor receptor: 4-(phenylamino)quinazoline- and 4-(phenylamino)pyrido[3,2-d]pyrimidine-6-acrylamides bearing additional solubilizing functions

4-Anilinoquinazoline- and 4-anilinopyrido[3,2-d]pyrimidine-6-acrylamides substituted with solubilizing 7-alkylamine or 7-alkoxyamine side chains were prepared by reaction of the corresponding 6-amines with acrylic acid or acrylic acid anhydrides. In the pyrido[3,2-d]pyrimidine series, the intermediate 6-amino-7-alkylamines were prepared from 7-bromo-6-fluoropyrido[3,2-d]pyrimidine via Stille coupling with the appropriate stannane under palladium(0) catalysis. This proved a versatile method for the introduction of cationic solubilizing side chains. The compounds were evaluated for their inhibition of phosphorylation of the isolated EGFR enzyme and for inhibition of EGF-stimulated autophosphorylation of EGFR in A431 cells and of heregulin-stimulated autophosphorylation of erbB2 in MDA-MB 453 cells. Quinazoline analogues with 7-alkoxyamine solubilizing groups were potent irreversible inhibitors of the isolated EGFR enzyme, with IC(50[app]) values from 2 to 4 nM, and potently inhibited both EGFR and erbB2 autophosphorylation in cells. 7-Alkylamino- and 7-alkoxyaminopyrido[3,2-d]pyrimidines were also irreversible inhibitors with equal or superior potency against the isolated enzyme but were less effective in the cellular autophosphorylation assays. Both quinazoline- and pyrido[3,2-d]pyrimidine-6-acrylamides bound at the ATP site alkylating cysteine 773, as shown by electrospray ionization mass spectrometry, and had similar rates of absorptive and secretory transport in Caco-2 cells. A comparison of two 7-propoxymorpholide analogues showed that the pyrido[3,2-d]pyrimidine-6-acrylamide had greater amide instability and higher acrylamide reactivity, being converted to glutathione adducts in cells more rapidly than the corresponding quinazoline. This difference may contribute to the observed lower cellular potency of the pyrido[3,2-d]pyrimidine-6-acrylamides. Selected compounds showed high in vivo activity against A431 xenografts on oral dosing, with the quinazolines being superior to the pyrido[3,2-d]pyrimidines. Overall, the quinazolines proved superior to previous analogues in terms of aqueous solubility, potency, and in vivo antitumor activity, and one example (CI 1033) has been selected for clinical evaluation.

Tyrosine kinase inhibitors. 16. 6,5,6-tricyclic benzothieno[3, 2-d]pyrimidines and pyrimido[5,4-b-] and -[4,5-b]ĭndoles as potent inhibitors of the epidermal growth factor receptor tyrosine kinase

Several elaborations of the fundamental anilinopyrimidine pharmacophore have been reported as potent and selective inhibitors of the epidermal growth factor receptor (EGFr) tyrosine kinase. This paper reports on a series of inhibitors whereby some 6,5-bicyclic heteroaromatic systems were fused through their C-2 and C-3 positions to this anilinopyrimidine pharmacophore. Although the resulting tricycles did not produce the enormous potency of some of the (5/6),6,6-bicyclic systems, the best of them had IC(50)s for the EGFr TK around 1 nM. Investigation of 4-position side chains in the indolopyrimidines confirmed that m-bromoaniline was an optimal substituent for potency. Investigation of substitution within the C-(benzo)ring of benzothienopyrimidines confirmed that introduction of an extra ring can change sharply the effects of substituents when compared to similar bicyclic nuclei, and only two substituents were found which even moderately enhanced inhibitory activity over the parent compound for this series.

Homoarcyriaflavin: Synthesis of Ring-Expanded Arcyriaflavin Analogues

The construction of the ring-expanded carbazole system, forming arcyriaflavin homologues, is efficiently accomplished by the reaction of 2,2'-bridged bis-indoles with 3,4-dibromo-2,5-dihydro-1H-2,5-pyrroledione derivatives under Grignard conditions. A ring size of up to nine members in the central ring is achievable. Substitutions either at the indole system or at the imide-N are also possible. The conformation of homoarcyriaflavins as a cross-link between the rigid arcyriaflavins and the flexible arcyriarubins was investigated by NMR, X-ray, and semiempiric quantum chemical calculation methods.

Tyrosine kinase inhibitors. 15. 4-(Phenylamino)quinazoline and 4-(phenylamino)pyrido[d]pyrimidine acrylamides as irreversible inhibitors of the ATP binding site of the epidermal growth factor receptor

A series of 6- and 7-acrylamide derivatives of the 4-(phenylamino)quinazoline and -pyridopyrimidine classes of epidermal growth factor receptor (EGFR) inhibitors were prepared from the corresponding amino compounds by reaction with either acryloyl chloride/base or acrylic acid/1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride. All of the 6-acrylamides, but only the parent quinazoline 7-acrylamide, were irreversible inhibitors of the isolated enzyme, confirming that the former are better-positioned, when bound to the enzyme, to react with the critical cysteine-773. Quinazoline, pyrido[3,4-d]pyrimidine, and pyrido[3,2-d]pyrimidine 6-acrylamides were all irreversible inhibitors and showed similar high potencies in the enzyme assay (likely due to titration of the available enzyme). However the pyrido[3,2-d]pyrimidine analogues were 2-6-fold less potent than the others in a cellular autophosphorylation assay for EGFR in A431 cells. The quinazolines were generally less potent overall toward inhibition of heregulin-stimulated autophosphorylation of erbB2 (in MDA-MB-453-cells), whereas the pyridopyrimidines were equipotent. Selected compounds were evaluated in A431 epidermoid and H125 non-small-cell lung cancer human tumor xenografts. The compounds showed better activity when given orally than intraperitoneally. All showed significant tumor growth inhibition (stasis) over a dose range. The poor aqueous solubility of the compounds was a drawback, requiring formulation as fine particulate emulsions.

Structure of the protein tyrosine kinase domain of C-terminal Src kinase (CSK) in complex with staurosporine

The crystal structure of the kinase domain of C-terminal Src kinase (CSK) has been determined by molecular replacement, co-complexed with the protein kinase inhibitor staurosporine (crystals belong to the space group P21212 with a=44.5 A, b=120.6 A, c=48.3 A). The final model of CSK has been refined to an R-factor of 19.9 % (Rfree=28.7 %) at 2.4 A resolution. The structure consists of a small, N-terminal lobe made up mostly of a beta-sheet, and a larger C-terminal lobe made up mostly of alpha-helices. The structure reveals atomic details of interactions with staurosporine, which binds in a deep cleft between the lobes. The polypeptide chain fold of CSK is most similar to c-Src, Hck and fibroblast growth factor receptor 1 kinase (FGFR1K) and most dissimilar to insulin receptor kinase (IRK). Interactions between the N and C-terminal lobe are mediated by the bound staurosporine molecule and by hydrogen bonds. In addition, there are several water molecules forming lobe-bridging hydrogen bonds, which may be important for maintaining the catalytic integrity of the kinase. Furthermore, the conserved Lys328 and Glu267 residues utilise water in the formation of a molecular pivot which is essential in allowing relative movement of the N and C-terminal lobes. An analysis of the residues around the ATP-binding site reveals structural differences with other protein tyrosine kinases. Most notable of these are different orientations of the conserved residues Asp332 and Phe333, suggesting that inhibitor binding proceeds via an induced fit. These structural observations have implications for understanding protein tyrosine kinase catalytic mechanisms and for the design of ATP-mimicking inhibitors of protein kinases.

Preparation of 4-(4'-Hydroxyanilino)-5-anilinophthalimide and 4,5-Bis-(4'-hydroxyanilino)-phthalimide by Microbial Hydroxylation

A microbial screening indicated that two fungal strains, Beauveria bassiana DSM 1344=ATCC 7159 and Cunninghamella elegans DSM 1908=ATCC 9245, as well as four bacterial strains belonging to the genus Streptomyces were able to hydroxylate 4,5-dianilinophthalimide (DAPH, CGP52411) to 4-(4'-hydroxyanilino)-5-anilinophthalimide. Cunninghamella elegans DSM 1908 turned out to be the most active biocatalyst and was also able to form the dihydroxy derivative, 4,5-bis(4'-hydroxyanilino)phthalimide. The reaction for the monohydroxylated biotransformation product was carried out on a preparative scale, and the culture conditions for the formation of 4-(4'-hydroxy- anilino)-5-anilinophthalimide with this strain were op-timized.

A potent protein-tyrosine kinase inhibitor which selectively blocks proliferation of epidermal growth factor receptor-expressing tumor cells in vitro and in vivo

A calculated 3-D model of the kinase domain of the epidermal growth factor receptor (EGF-R) protein-tyrosine kinase (PTK) was used to develop a pharmacophore model for ATP-competitive inhibitors and, subsequently, a new class of selective EGF-R kinase inhibitors. CGP 59326A, a highly selective and potent inhibitor of the EGF-R in vitro, inhibited the proliferation of EGF-R-expressing epithelial lines, while having little anti-proliferative activity against EGF-R-negative lines. In contrast to previously described inhibitors, CGP 59326A had potent and selective in vivo anti-tumor activity at well-tolerated doses against EGF-R-expressing tumors (e.g., ED50 of 0.78 to 1.5 mg/kg for inhibition of A431 tumor growth). CGP 59326A inhibited growth of human tumor xenografts expressing the EGF-R but showed little activity against EGF-R-negative xenografts. Combination of CGP 59326A with cytotoxic agents resulted in tumor regression and cures. The high selectivity and attractive biological profile of CGP 59326A suggest that it could have therapeutic value in the treatment of proliferative diseases which involve mitogenic signaling from the EGF-R.

Inhibition of epidermal growth factor-mediated ERK1/2 activation by in situ electroporation of nonpermeant [(alkylamino)methyl]acrylophenone derivatives

The interruption of signaling cascades in intact cells through the introduction of nonpermeant compounds inferred by in vitro studies to specifically inhibit epidermal growth factor (EGF) receptor (EGF-R) function is described. Two nonpermeant [(alkylamino)methyl]acrylophenone derivatives, [(dimethylamino)methyl] acrylo-para-[(benzoylsulfonyl)-oxy]phenone and [(dimethylamino)-methyl]acrylo-para-[(hydroxy-benzoylsulfonyl++ +)-oxy]phenone, were introduced by in situ electroporation into mouse or rat fibroblasts growing on indium-tin oxide-coated glass. Cells were subsequently stimulated with growth factors and assessed for activation of a downstream target, the extracellular signal-regulated kinase (ERK1/2), by probing with specific antibodies. Electrodes and slides were configured to provide non-electroporated control cells side by side with the electroporated ones, both growing on the same type of indium-tin oxide-coated glass surface. Using this set-up, these compounds could inhibit EGF- but not platelet-derived growth factor (PDGF)-mediated ERK1/2 activation in vivo. These results demonstrate the potential of the in situ electroporation approach for the study of tyrosine kinase action using selective but nonpermeant inhibitors that would otherwise be ineffective in intact cells.

Structures of staurosporine bound to CDK2 and cAPK--new tools for structure-based design of protein kinase inhibitors

Protein kinases are involved in a wide variety of signal transduction processes; their deregulation has been implicated in a number of human diseases, including cancer and disorders of the immune system. The recently determined structures of two protein kinases, cAPK and CDK2, in complex with an inhibitor, staurosporine, provide a detailed account of inhibitor-kinase interactions and inhibitor selectivity.

Epidermal growth factor receptor (EGFR) and EGFR mutations, function and possible role in clinical trials

The epidermal growth factor receptor (EGFR) is a growth factor receptor that induces cell differentiation and proliferation upon activation through the binding of one of its ligands. The receptor is located at the cell surface, where the binding of a ligand activates a tyrosine kinase in the intracellular region of the receptor. This tyrosine kinase phosphorylates a number of intracellular substrates that activates pathways leading to cell growth, DNA synthesis and the expression of oncogenes such as fos and jun. EGFR is thought to be involved the development of cancer, as the EGFR gene is often amplified, and/or mutated in cancer cells. In this review we will focus on: (I) the structure and function of EGFR, (II) implications of receptor/ligand coexpression and EGFR mutations or overexpression, (III) its effect on cancer cells, (IV) the development of the malignant phenotype and (V) the clinical aspects of therapeutic targeting of EGFR.

Use of a pharmacophore model for the design of EGF-R tyrosine kinase inhibitors: 4-(phenylamino)pyrazolo[3,4-d]pyrimidines

In the course of the random screening of a pool of CIBA chemicals, the two pyrazolopyrimidines 1 and 2 have been identified as fairly potent inhibitors of the EGF-R tyrosine kinase. Using a pharmacophore model for ATP-competitive inhibitors interacting with the active site of the EGF-R protein tyrosine kinase (PTK), the class of the pyrazolo[3,4-d]pyrimidines was then optimized in an interactive process leading to a series of 4-(phenylamino)-1H-pyrazolo[3,4-d]-pyrimidines as highly potent inhibitors of the EGF-R tyrosine kinase. The most potent compounds 13, 14, 15, 17, 19, 22, 26, 28, and 30 of this series inhibited the EGF-R PTK with IC50 values below 10 nM. High selectivity toward a panel of nonreceptor tyrosine kinases (c-Src, v-Abl and serine/threonine kinases (PKC alpha, CDK1) was observed. In cells, EGF-stimulated cellular tyrosine phosphorylation was inhibited by compounds 13, 15, 19, 22, and 23 at IC50 values below 50 nM, whereas PDGF-induced tyrosine phosphorylation was not affected by concentrations up to 10 microM, thus indicating high selectivity for the inhibition of the ligand-activated EGF-R signal transduction pathway. Compounds 15 and 19 inhibited proliferation of the EGF-dependent MK cell line with IC50 values below 0.5 microM. In addition, two compounds, 9 and 11, showing satisfactory oral bioavailability in mice after oral administration, exhibited good in vivo efficacy at doses of 12.5 and 50 mg/kg in a nude mouse tumor model using xenografts of the EGF-R overexpressing A431 cell line. From SAR studies, a binding mode for 4-(phenylamino)-1H-pyrazolo[3,4-d]pyrimidines, especially for compound 15, at the ATP-binding site of the EGF-R tyrosine kinase is proposed. 4-(Phenylamino)-1H-pyrazolo[3,4-d]pyrimidines represent a new class of highly potent tyrosine kinase inhibitors which preferentially inhibit the EGF-mediated signal transduction pathway and have the potential for further evaluation as anticancer agents.