Discovery of potent and selective SH2 inhibitors of the tyrosine kinase ZAP-70

Design, synthesis and docking studies of novel 4-aminophenol-1,2,4-oxadiazole hybrids as apoptosis inducers against triple negative breast cancer cells targeting MAP kinase

In our study, a series of novel 4-aminophenol benzamide-1,2,4-oxadiazole hybrid analogues have been designed and synthesized by condensing 4-hydroxyphenyl arylamides (3a-c) and 5-chloromethyl-3-aryl-1,2,4-oxadiazoles (6a-d). The structure of the synthesised compounds was verified by various spectroscopic techniques (1H NMR, 13C NMR, IR and LC-MS). All the prepared compounds were subjected to in silico and in vitro antiproliferative study against TNBC cell lines MDA-MB-468 and MDA-MB-231. The investigations revealed that compound 7k significantly promoted apoptosis against MDA-MB-468 and MDA-MB-231 cells with IC50 values of 22.31 µM and 26.27 µM, respectively. Compound 7k interacted with crucial active sites of MAPK and exhibited the highest docking score of -7.06 kcal/mol. Docking was validated with molecular dynamic studies with simulation for 100 ns, depicting various stable interactions with MAPK. Consequently, 7k forms stable H-Bonds and π-π stacking with amino acid residues along with π-cation. Our investigations reveal that the in vitro antiproliferative study of 7k was in good correlation with the in silico studies. Hence, 7k serves as a potential novel lead for the inhibition of TNBCs by downregulating MAPK P38.Communicated by Ramaswamy H. Sarma.

Discovery and Structural Optimization of Covalent ZAP-70 Kinase Inhibitors against Psoriasis

Psoriasis is a chronic inflammatory skin disease closely related with T cells, and its management remains a challenge. Novel targets and associated drugs are urgently needed. Zeta-chain-associated protein kinase 70 kDa (ZAP-70) has been recognized as a potential target for treating autoimmune diseases due to its crucial role in T cell receptor signaling. In our previous work, we identified a potent and selective covalent ZAP-70 inhibitor with anti-inflammatory activity in vitro. Herein, we report the structural optimization of covalent ZAP-70 inhibitors. Our efforts led to the discovery of compound 25 (RDN2150), which exhibited potent inhibitory activity against ZAP-70 and favorable selectivity. It also demonstrated promising inhibitory effects on T cell activation and inflammatory cytokine production. Furthermore, a topical application of 25 resulted in significant efficacy in an imiquimod-induced psoriasis mouse model. Overall, these findings present the basis of a promising strategy for the treatment of psoriasis by targeting ZAP-70.

Convenient one-pot synthesis of 1,2,4-oxadiazoles and 2,4,6-triarylpyridines using graphene oxide (GO) as a metal-free catalyst: importance of dual catalytic activity

A convenient and efficient process for the synthesis of 3,5-disubstituted 1,2,4-oxadiazoles and 2,4,6-triarylpyridines has been described using an inexpensive, environmentally benign, metal-free heterogeneous carbocatalyst, graphene oxide (GO). GO plays a dual role of an oxidizing agent and solid acid catalyst for synthesizing 1,2,4-oxadiazoles and triarylpyridines. This dual catalytic activity of GO is due to the presence of oxygenated functional groups which are distributed on the nanosheets of graphene oxide. A broad scope of substrate applicability and good sustainability is offered in this developed protocol. The results of a few control experiments reveal a plausible mechanism and the role of GO as a catalyst was confirmed by FTIR, XRD, SEM, and HR-TEM analysis.

Discovery of a potent, selective, and covalent ZAP-70 kinase inhibitor

ZAP-70 (zeta-chain associated protein kinase 70 kDa) signaling pathway and its functions have been involved in the development and adaptive immune signaling of T cell. It thus represents a promising target for autoimmune diseases. Although reversible ZAP-70 kinase domain inhibitors have been developed, they are either weak or nonselective. We report herein the structure-guided development of the first potent and covalent inhibitor of ZAP-70 kinase domain. In particular, compound 18 (RDN009) showed good selectivity for ZAP-70 over structurally related Syk, and displayed potent inhibitory effects on T cell proliferation, activation, and inflammatory cytokine production. A mass spectrometry analysis further confirmed the covalent linkage between the inhibitor and ZAP-70 protein at C346. Overall, the covalent inhibitor RDN009 represents a potent and selective probe of ZAP-70 for further development for treatment of autoimmune diseases.

Emerging Marine Immunomodulatory Small-molecules (2010- Present)

Background:

Immunomodulation-based therapy has achieved a breakthrough in the last decade, which stimulates the passion of searching for potential immunomodulatory substances in recent years.

Objective:

Marine natural products are a unique source of immunomodulatory substances. This paper summarized the emerging marine natural small-molecules and related synthesized derivatives with immunomodulatory activities to provide readers an overview of these bioactive molecules and their potential in immunomodulation therapy.

Conclusion:

An increasing number of immunomodulatory marine small-molecules with diverse intriguing structure-skeletons were discovered. They may serve as a basis for further studies of marine natural products for their chemistry, related mechanism of action and structure- activity relationships.

Recent Developments in the Synthesis, Chemistry and Applications of the Fully Unsaturated 1,2,4-Oxadiazoles

Recent major developments in the synthesis (including solid phase methodologies), chemistry and applications of the fully unsaturated 1,2,4-oxadiazole nucleus are reviewed. The review covers the years 1995–2000.

Identification of Inhibitors of the Association of ZAP-70 with the T Cell Receptor by High-Throughput Screen

ZAP-70 is a critical molecule in the transduction of T cell antigen receptor signaling and the activation of T cells. Upon activation of the T cell antigen receptor, ZAP-70 is recruited to the intracellular ζ-chains of the T cell receptor, where ZAP-70 is activated and colocalized with its substrates. Inhibitors of ZAP-70 could potentially function as treatments for autoimmune diseases or organ transplantation. In this work, we present the design, optimization, and implementation of a screen for inhibitors that would disrupt the interaction between ZAP-70 and the T cell antigen receptor. The screen is based on a fluorescence polarization assay for peptide binding to ZAP-70.

An Efficient One-Pot Synthesis of 3-Aryl-5-(Dialkoxymethyl)-1,2,4-Oxadiazoles under Solvent-Free Conditions

An efficient and simple synthesis of 3-aryl-5-(dialkoxymethyl)-1,2,4-oxadiazoles is described. The in situ prepared amidoximes from the reaction between nitriles and hydroxylamine are condensed with alkyl 2,2-dialkoxyacetates under solvent-free conditions to produce the title compounds in excellent yields.

N-heterocyclic carbenes (NHC) with 1,2,4-oxadiazole-substituents related to natural products: synthesis, structure and potential antitumor activity of some corresponding gold(I) and silver(I) complexes

This work presents the synthesis, characterization and application of eleven new gold (I) complexes 13-23 with 1,2,4-oxadiazole-containing N-heterocyclic carbene (NHC) ligands and of the NHC silver(I) complex 24. The 1,2,4-oxadiazole unit, which can be found in a variety of biologically active natural products such as phidianidines or quisqualic acid, was incorporated, along with a variety of other biologically active moieties (anthracene, indole, 2-pyridine, 2,3,4,5-tetra-O-acetyl-D-glucopyranose, quincorine and quincoridine), in order to change the lipophilicity of the complexes, so that the transport of the active units (M-NHC) though the cell wall barrier is facilitated. The biological activity of the complexes was investigated. In vitro assessment of anti-tumor activity in a panel of 12 human tumor cell lines by a monolayer assay revealed impressive potency (mean IC50 < 0.1 μM) and tumor selectivity for 6 compounds, with individual IC50 values in the low nanomolar range. The solid state structures of compounds 13, 14, 15, 17, 18, 19 and 24 were determined by X-ray diffraction analyses.

An efficient mEthod for the One-Pot Tandem Synthesis of 3,5-Disubstituted-1,2,4-Oxadiazoles from Benzyl Halides

The first example of a one-pot tandem approach for the synthesis of 3,5-disubstituted-1,2,4-oxadiazole derivatives from benzyl halides and amidoxime is reported. Derivatives of 3,5-disubstituted 1,2,4-oxadiazole were obtained in excellent yields under mild conditions using DMSO in the absence of an additional oxidant. Benzyl bromides bearing a range of substituents proved to be suitable substrates for this method which provides a very efficient and convenient application of the Kornblum oxidation.

Synthesis of 2-(1,2,4-oxadiazol-3-yl)quinazolin-4(3H)-ones from diaminoglyoxime-based nitrones

Various 2-[5-(aryl)-1,2,4-oxadiazol-3-yl]quinazolin-4(3H)-ones have been synthesized from the reaction of diaminoglyoxime-based nitrones with methyl 2-aminobenzoate or 2-aminobenzamide in the presence of acetic acid at 100 °C. The reaction was extended as a one-pot three-component approach starting from diaminoglyoxime, aldehyde and methyl 2-aminobenzoate.

Modification by covalent reaction or oxidation of cysteine residues in the tandem-SH2 domains of ZAP-70 and Syk can block phosphopeptide binding

Zeta-chain associated protein of 70 kDa (ZAP-70) and spleen tyrosine kinase (Syk) are non-receptor tyrosine kinases that are essential for T-cell and B-cell antigen receptor signalling respectively. They are recruited, via their tandem-SH2 (Src-homology domain 2) domains, to doubly phosphorylated immunoreceptor tyrosine-based activation motifs (ITAMs) on invariant chains of immune antigen receptors. Because of their critical roles in immune signalling, ZAP-70 and Syk are targets for the development of drugs for autoimmune diseases. We show that three thiol-reactive small molecules can prevent the tandem-SH2 domains of ZAP-70 and Syk from binding to phosphorylated ITAMs. We identify a specific cysteine residue in the phosphotyrosine-binding pocket of each protein (Cys39 in ZAP-70, Cys206 in Syk) that is necessary for inhibition by two of these compounds. We also find that ITAM binding to ZAP-70 and Syk is sensitive to the presence of H2O2 and these two cysteine residues are also necessary for inhibition by H2O2. Our findings suggest a mechanism by which the reactive oxygen species generated during responses to antigen could attenuate signalling through these kinases and may also inform the development of ZAP-70 and Syk inhibitors that bind covalently to their SH2 domains.

Synthesis and characterization of novel bioactive 1,2,4-oxadiazole natural product analogs bearing the N-phenylmaleimide and N-phenylsuccinimide moieties

Taking into consideration the biological activity of the only natural products containing a 1,2,4-oxadiazole ring in their structure (quisqualic acid and phidianidines A and B), the natural product analogs 1-(4-(3-tert-butyl-1,2,4-oxadiazol-5-yl)phenyl)pyrrolidine-2,5-dione (4) and 1-(4-(3-tert-butyl-1,2,4-oxadiazol-5-yl)phenyl)-1H-pyrrole-2,5-dione (7) were synthesized starting from 4-(3-tert-butyl-1,2,4-oxadiazol-5-yl)aniline (1) in two steps by isolating the intermediates 4-(4-(3-tert-butyl-1,2,4-oxadiazol-5-yl)phenylamino)-4-oxobutanoic acid (3) and (Z)-4-(4-(3-tert-butyl-1,2,4-oxadiazol-5-yl)phenylamino)-4-oxobut-2-enoic acid (6). The two natural product analogs 4 and 7 were then tested for antitumor activity toward a panel of 11 cell lines in vitro by using a monolayer cell-survival and proliferation assay. Compound 7 was the most potent and exhibited a mean IC₅₀ value of approximately 9.4 µM. Aniline 1 was synthesized by two routes in one-pot reactions starting from tert-butylamidoxime and 4-aminobenzoic acid or 4-nitrobenzonitrile. The structures of compounds 1, 2, 4, 5 and 6 were confirmed by X-ray crystallography.

Synthesis and bioassay of a new class of furanyl-1,3,4-oxadiazole derivatives

Tyrosinase enzyme is a monophenol monoxygenase enzyme, which plays an important role in human as a rate limiting step enzyme for different specific metabolic pathways, as well as its useful application in industry and agriculture. So this study was carried out to test the effect of newly prepared compounds containing 1,3,4-oxadiazoles with different substituted groups on tyrosinase enzyme activity, hoping to use them in the treatment of some diseases arising from tyrosinase activity disorders such as Parkinson's disease, schizophrenia, autism, attention deficit, hyperactivity disorder, and cancer.

Efficient delivery of cell impermeable phosphopeptides by a cyclic peptide amphiphile containing tryptophan and arginine

Phosphopeptides are valuable reagent probes for studying protein-protein and protein-ligand interactions. The cellular delivery of phosphopeptides is challenging because of the presence of the negatively charged phosphate group. The cellular uptake of a number of fluorescent-labeled phosphopeptides, including F'-GpYLPQTV, F'-NEpYTARQ, F'-AEEEIYGEFEAKKKK, F'-PEpYLGLD, F'-pYVNVQN-NH2, and F'-GpYEEI (F' = fluorescein), was evaluated in the presence or absence of a [WR]4, a cyclic peptide containing alternative arginine (R) and tryptophan (W) residues, in human leukemia cells (CCRF-CEM) after 2 h incubation using flow cytometry. [WR]4 improved significantly the cellular uptake of all phosphopeptides. PEpYLGLD is a sequence that mimics the pTyr1246 of ErbB2 that is responsible for binding to the Chk SH2 domain. The cellular uptake of F'-PEpYLGLD was enhanced dramatically by 27-fold in the presence of [WR]4 and was found to be time-dependent. Confocal microscopy of a mixture of F'-PEpYLGLD and [WR]4 in live cells exhibited intracellular localization and significantly higher cellular uptake compared to that of F'-PEpYLGLD alone. Transmission electron microscopy (TEM) and isothermal calorimetry (ITC) were used to study the interaction of PEpYLGLD and [WR]4. TEM results showed that the mixture of PEpYLGLD and [WR]4 formed noncircular nanosized structures with width and height of 125 and 60 nm, respectively. ITC binding studies confirmed the interaction between [WR]4 and PEpYLGLD. The binding isotherm curves, derived from sequential binding models, showed an exothermic interaction driven by entropy. These studies suggest that amphiphilic peptide [WR]4 can be used as a cellular delivery tool of cell-impermeable negatively charged phosphopeptides.

Design and synthesis of 3,5-disubstituted-1,2,4-oxadiazoles as potent inhibitors of phosphodiesterase4b2

A series of 3,5-disubstituted-1,2,4-oxadiazoles has been prepared and evaluated for phosphodiesterase inhibition (PDE4B2). Among the prepared 3,5-disubstituted-1,2,4-oxadiazoles, compound 9a is the most potent inhibitor (PDE4B2 IC(50)  = 5.28 μm). Structure-activity relationship studies of 3,5-disubstituted-1,2,4-oxadiazoles revealed that substituents 3-cyclopentyloxy-4-methoxyphenyl group at 3-position and cyclic ring bearing heteroatoms at 5-position are important for activity. Molecular modeling study of the 3,5-disubstituted-1,2,4-oxadiazoles with PDE4B has shown similar interactions of 3-cyclopentyloxy-4-methoxyphenyl group; however, heteroatom ring is slightly deviating when compared to Piclamilast. 3-(3-Cyclopentyloxy-4-methoxyphenyl)-5-(piperidin-4-yl)-1,2,4-oxadiazole (9a) exhibited good analgesic and antiinflammatory activities in formalin-induced pain in mice and carrageenan-induced paw edema model in rat.

An extremely simple dibenzopentalene synthesis from 2-bromo-1-ethynylbenzenes using nickel(0) complexes: construction of its derivatives with various functionalities

Nice and easy: A very simple synthesis for dibenzopentalenes, which starts from 1-bromo-2-ethynylbenzenes, has been developed. It uses Ni(0) complexes (see scheme), from which a relatively stable Ni(II) complex as an important intermediate has been isolated. Dibenzopentalenes with various functional groups can be prepared by the procedure, and their electronic properties are consistent with theoretical calculations.An extremely simple dibenzopentalene synthesis from readily available 2-bromo-1-ethynylbenzenes using a nickel(0) complex is described. Although the yields are moderate, the formation of three C-C bonds in a single process and the high availability of the starting materials are important advantages of this reaction. The corresponding aryl-nickel(II) complex as an important intermediate was isolated as relatively stable crystals, and the structure was confirmed by X-ray crystallographic analysis. The high stability of this complex should play a key role in this reaction. The reaction is applicable to the preparation of dibenzopentalenes bearing various functional groups. Their electronic properties are consistent with theoretical calculations. The cyclic voltammograms of these compounds reveal highly amphoteric redox properties. In particular, the electron-donating property of a tetramethoxy derivative is greater than that of oligothiophenes and dibenzodithiophenes and almost comparable to that of pentacene.

Structure-activity relationship studies of 5-benzylaminoimidazo[1,2-c]pyrimidine-8-carboxamide derivatives as potent, highly selective ZAP-70 kinase inhibitors

Zeta-associated protein, 70 kDa (ZAP-70), a spleen tyrosine kinase (Syk) family kinase, is normally expressed on T cells and natural killer cells and plays a crucial role in activation of the T cell immunoresponse. Thus, selective ZAP-70 inhibitors might be useful not only for treating autoimmune diseases, but also for suppressing organ transplant rejection. In our recent study on the synthesis of Syk family kinase inhibitors, we discovered that novel imidazo[1,2-c]pyrimidine-8-carboxamide derivatives possessed potent ZAP-70 inhibitory activity with good selectivity for ZAP-70 over other kinases. In particular, compound 26 showed excellent ZAP-70 kinase inhibition and high selectivity for ZAP-70 over structurally related Syk. The discovery of a potent, highly selective ZAP-70 inhibitor would contribute a new therapeutic tool for autoimmune diseases and organ transplant medication.