Discovery of 3-hydroxy-4-carboxyalkylamidino-5-arylamino-isothiazoles as potent MEK1 inhibitors

Pharmacological SARM1 inhibition protects axon structure and function in paclitaxel-induced peripheral neuropathy

Axonal degeneration is an early and ongoing event that causes disability and disease progression in many neurodegenerative disorders of the peripheral and central nervous systems. Chemotherapy-induced peripheral neuropathy (CIPN) is a major cause of morbidity and the main cause of dose reductions and discontinuations in cancer treatment. Preclinical evidence indicates that activation of the Wallerian-like degeneration pathway driven by sterile alpha and TIR motif containing 1 (SARM1) is responsible for axonopathy in CIPN. SARM1 is the central driver of an evolutionarily conserved programme of axonal degeneration downstream of chemical, inflammatory, mechanical or metabolic insults to the axon. SARM1 contains an intrinsic NADase enzymatic activity essential for its pro-degenerative functions, making it a compelling therapeutic target to treat neurodegeneration characterized by axonopathies of the peripheral and central nervous systems. Small molecule SARM1 inhibitors have the potential to prevent axonal degeneration in peripheral and central axonopathies and to provide a transformational disease-modifying treatment for these disorders.

Using a biochemical assay for SARM1 NADase we identified a novel series of potent and selective irreversible isothiazole inhibitors of SARM1 enzymatic activity that protected rodent and human axons in vitro. In sciatic nerve axotomy, we observed that these irreversible SARM1 inhibitors decreased a rise in nerve cADPR and plasma neurofilament light chain released from injured sciatic nerves in vivo. In a mouse paclitaxel model of CIPN we determined that Sarm1 knockout mice prevented loss of axonal function, assessed by sensory nerve action potential amplitudes of the tail nerve, in a gene-dosage-dependent manner. In that CIPN model, the irreversible SARM1 inhibitors prevented loss of intraepidermal nerve fibres induced by paclitaxel and provided partial protection of axonal function assessed by sensory nerve action potential amplitude and mechanical allodynia.

Synthesis of Isoselenazoles and Isothiazoles from Demethoxylative Cycloaddition of Alkynyl Oxime Ethers

A general method for the synthesis of isoselenazoles and isothiazoles has been developed by the base-promoted demethoxylative cycloaddition of alkynyl oxime ethers using the cheap and inactive Se powder and Na₂S as selenium and sulfur sources. This transformation features the direct construction of N-, Se-, and S-containing heterocycles through the formation of N-Se/S and C-Se/S bonds in one-pot reactions with excellent functional group tolerance.

Access to 4-substituted isothiazoles through three-component cascade annulation and their application in C–H activation

The use of EtOCS₂k enabled the annulation of isopropene derivatives with NH₄I, affording various 4-substituted isothiazoles in good yields.

The 5-hydrazino-3-methylisothiazole-4-carboxylic acid, its new 5-substituted derivatives and their antiproliferative activity

Currently, the basic method of treatment of colon cancer is surgery. The range of anticancer drugs used in the treatment of colorectal cancer is small and is based mainly on systemic combination chemotherapy. As a result of the designed syntheses, we received new isothiazole derivatives with anticancer activity. The synthesized 5-hydrazino-3-methylisothiazole-4-carboxylic acid has never been obtained before. It is also a substrate for the synthesis of its innovative derivatives, i.e. compounds that are Schiff bases. The identification of the structure of new compounds was carried out using mass spectrometry (MS), proton nuclear magnetic resonance spectroscopy (¹H NMR), carbon nuclear magnetic resonance spectroscopy (¹³C NMR) and infrared spectroscopy (IR). Potential antitumor activity was confirmed in antiproliferative MTT and SRB tests. The selected, most biologically active substances were characterized by high selectivity towards leukemia and colon cancer cell lines. They caused high inhibition of proliferation of human biphenotypic B cell myelomonocytic leukemia MV4-11 (13 compounds), human colon adenocarcinoma cell lines sensitive LoVo (8 compounds) and resistant to doxorubicin LoVo/DX (12 compounds). However, in the conducted studies, their activity against breast adenocarcinoma MCF-7 and normal non-tumorigenic epithelial cell line derived from mammary gland MCF-10A was substantially lower. The result of this work is claimed Polish patent application.

Part II: New candidates of pyrazole-benzimidazole conjugates as checkpoint kinase 2 (Chk2) inhibitors

The development of checkpoint kinase 2 (Chk2) inhibitors for the treatment of cancer has been an ongoing and attractive objective in drug discovery. In this study, twenty-one feasible pyrazole-benzimidazole conjugates were synthesized to study their effect against Chk2 activity using Checkpoint Kinase Assay. The antitumor activity of these compounds was investigated using SRB assay. A potentiation effect of the synthesized Chk2 inhibitors was also investigated using the genotoxic anticancer drugs cisplatin and doxorubicin on breast carcinoma, (ER+) cell line (MCF-7). In vivo Chk2 and antitumor activities of 8d as a single-agent, and in combination with doxorubicin, were evaluated in breast cancer bearing animals induced by N-methylnitrosourea. The effect of 8d alone and in combination with doxorubicin was also studied on cell-cycle phases of MCF-7 cells using flow cytometry analysis. The results revealed their potencies as Chk2 inhibitors with IC₅₀ ranges from 9.95 to 65.07 nM. Generally the effect of cisplatin or doxorubicin was potentiated by the effect of most of the compounds that were studied. The in vivo results indicated that the combination of 8d and doxorubicin inhibited checkpoint kinase activity more than either doxorubicin or 8d alone. There was a positive correlation between checkpoint kinase inhibition and the improvement observed in histopathological features. Single dose treatment with doxorubicin or 8d produced S phase cell cycle arrest whereas their combination created cell cycle arrest at G2/M from 8% in case of doxorubicin to 51% in combination. Gold molecular modelling studies displayed a high correlation to the biological results.

Synthesis, fungicidal evaluation and 3D-QSAR studies of novel 1,3,4-thiadiazole xylofuranose derivatives

1,3,4-Thiadiazole and sugar-derived molecules have proven to be promising agrochemicals with growth promoting, insecticidal and fungicidal activities. In the research field of agricultural fungicide, applying union of active group we synthesized a new set of 1,3,4-thiadiazole xylofuranose derivatives and all of the compounds were characterized by ¹H NMR and HRMS. In precise toxicity measurement, some of compounds exhibited more potent fungicidal activities than the most widely used commercial fungicide Chlorothalonil, promoting further research and development. Based on our experimental data, 3D-QSAR (three-dimensional quantitative structure-activity relationship) was established and investigated using comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) techniques, helping to better understand the structural requirements of lead compounds with high fungicidal activity and environmental compatibility.

Part I: Design, synthesis and biological evaluation of novel pyrazole-benzimidazole conjugates as checkpoint kinase 2 (Chk2) inhibitors with studying their activities alone and in combination with genotoxic drugs

Activated checkpoint kinase 2 (Chk2) is a tumor suppressor as one of the main enzymes that affect the cell cycle. 2-Biarylbenzimidazoles are potent selective class of Chk2 inhibitors; the structure-based design was applied to synthesize a new series of this class with replacing the lateral aryl group by substituted pyrazoles. Ten pyrazole-benzimidazole conjugates from the best fifty candidates according to docking programs have been subjected to chemical synthesis in this study. The activities of the conjugates 5-14 as checkpoint kinase inhibitors and as antitumor alone and in combination with genotoxic drugs were evaluated. The effect of compounds 7 and 12 on cell-cycle phases was analyzed by flow cytometry analysis. Antitumor activity of compounds 7 and 12 as single-agents and in combinations with doxorubicin was assessed in breast cancer bearing animals induced by MNU. The Results indicated that compounds 5-14 inhibited Chk2 activity with high potency (IC₅₀ 52.8 nM-5.5 nM). The cytotoxicity of both cisplatin and doxorubicin were significantly potentiated by the most of the conjugates against MCF-7 cell lines. Compounds 7 and 12 and their combinations with doxorubicin induced the cell cycle arrest in MCF-7 cells. Moreover, compound 7 exhibited marked higher antitumor activity as a single agent in animals than it's combination with doxorubicin or doxorubicin alone. The combination of compound 12 with doxorubicin was greatly effective on animal than their single-dose treatment. In conclusion, pyrazole-benzimidazole conjugates are highly active Chk2 inhibitors that have anticancer activity and potentiate activity of genotoxic anticancer therapies and deserve further evaluations.

Ring transformation of (4-chloro-5H-1,2,3-dithiazol-5-ylidene)acetonitriles to 3-haloisothiazole-5-carbonitriles

Improved conditions for the ring transformation of 1,2,3-dithiazoles into isothiazole-5-carbonitriles are presented together with mechanistic rationale.

New small-molecule inhibitors of mitogen-activated protein kinase kinase

BACKGROUND

Overexpression of the Ras/Raf/MEK/ERK (extracellular-signal-regulated kinase) pathway is associated with the formation, progression and survival of tumours and has also been implicated in a diverse range of therapeutic areas such as arthritis, organ transplant rejection, asthma and developmental disorders. One approach to down regulation of this pathway is through the inhibition of mitogen-activated protein kinase kinase 1/2 (MEK1/2).

OBJECTIVE

The importance of the mitogen-activated protein kinase (MAPK) pathway, MEK1/2 as a therapeutic target and early MEK1/2 inhibitors is discussed, followed by an overview of recent patent activity in the area.

METHODS

The patent literature was searched for inhibitors of MEK1/2 published within the last three years; these results are described. Other relevant publications that provide further insight into the discovery and development of these compounds are also discussed.

CONCLUSION

The determination of a crystal structure with inhibitor bound has allowed the design of exquisitely selective and potent inhibitors of MEK1/2. Several allosteric inhibitors have advanced to clinical trial and shown some efficacy in cancer as single agents, but the future application of MEK1/2 inhibitors is likely to be either in combination with other therapies or in disorders which are genetically defined as being dependent on the MAPK pathway.

Silver-mediated palladium-catalyzed direct C-H arylation of 3-bromoisothiazole-4-carbonitrile

Silver(I) fluoride-mediated Pd-catalyzed C-H direct arylation/heteroarylation of 3-bromoisothiazole-4-carbonitrile (1a) gives twenty-four 5-aryl/heteroaryl-3-bromoisothiazole-4-carbonitriles. The reaction was partially optimized with respect to catalyst, ligand, and base. During this study 3,3'-dibromo-5,5'-biisothiazole-4,4'-dicarbonitrile (3a) was isolated as a byproduct and subsequently prepared via the silver-mediated Pd-catalyzed oxidative dimerization of 3-bromoisothiazole-4-carbonitrile in 67% yield. The analogous phenylation and oxidative dimerization of 3-chloroisothiazole-4-carbonitrile (1b) gave 3-chloro-5-phenylisothiazole-4-carbonitrile (4) and 3,3'-dichloro-5,5'-biisothiazole-4,4'-dicarbonitrile (3b) in 96% and 69% yields, respectively.

Antipoliovirus activity and mechanism of action of 3-methylthio-5-phenyl-4-isothiazolecarbonitrile

Our previous studies described the synthesis and the antiviral activity of 3,4,5-trisubstituted isothiazole derivatives that were found to be particularly effective against enteroviruses. Compound 3-methylthio-5-phenyl-4-isothiazolecarbonitrile (IS-2) exhibited an interesting anti-poliovirus activity with a high selectivity index. In the present study we investigated the mechanism of action of this compound. Studies on the time of IS-2 addition to poliovirus type 1 infected cells suggested that the compound may inhibit some early process of viral replication. In order to determine its mechanism of action, we evaluated the rate of attachment and internalization of purified [³H]uridine-labeled poliovirus to HEp-2 cells in the presence or absence of IS-2. No effect on poliovirus adsorption and internalization to host cells was detected. We also investigated the influence of the compound on virus uncoating using labeled poliovirus and measuring the radioactivity of oligoribonucleotides formed from viral RNA susceptible to ribonuclease. These experiments demonstrated that poliovirus uncoating is influenced by IS-2 action.

Biochemical and cellular characterization of VRX0466617, a novel and selective inhibitor for the checkpoint kinase Chk2

VRX0466617 is a novel selective small-molecule inhibitor for Chk2 discovered through a protein kinase screening program. In this study, we provide a detailed biochemical and cellular characterization of VRX0466617. We show that VRX0466617 blocks the enzymatic activity of recombinant Chk2, as well as the ionizing radiation (IR)-induced activation of Chk2 from cells pretreated with the compound, at doses between 5 and 10 micromol/L. These doses of VRX0466617 inhibited, to some extent, the phosphorylation of Chk2 Ser(19) and Ser(33-35), but not of Chk2 Thr(68), which is phosphorylated by the upstream ataxia-telangiectasia mutated (ATM) kinase. Interestingly, VRX0466617 induced the phosphorylation of Chk2 Thr(68) even in the absence of DNA damage, arising from the block of its enzymatic activity. VRX0466617 prevented the IR-induced Chk2-dependent degradation of Hdmx, concordant with the in vivo inhibition of Chk2. Analysis of ATM/ATM and Rad3-related substrates Smc1, p53, and Chk1 excluded a cross-inhibition of these kinases. VRX0466617 did not modify the cell cycle phase distribution, although it caused an increase in multinucleated cells. Whereas VRX0466617 attenuated IR-induced apoptosis, in short-term assays it did not affect the cytotoxicity by the anticancer drugs doxorubicin, Taxol, and cisplatin. These results underscore the specificity of VRX0466617 for Chk2, both in vitro and in vivo, and support the use of this compound as a biological probe to study the Chk2-dependent pathways.

3,4,5-Triarylisothiazoles via C–C coupling chemistry

The regiocontrolled preparation of triarylisothiazoles is presented. 3-Halo-5-phenylisothiazole-4-carbonitriles, 1 (hal=Cl) and 18 (hal=I), are converted into the corresponding 4-bromo derivatives 5 (3-hal=Cl) and 24 (3-hal=I) via a Hunsdiecker strategy while the 4-iodo analogues 7 (3-hal=Cl) and 22 (3-hal=I) are prepared via a Hoffmann and Sandmeyer strategy. Regioselective Suzuki, Stille and Negishi reactions occur at C-4 with both the 4-bromo- and 4-iodoisothiazoles 5 and 7 , the latter being more reactive than the former. 3-Iodoisothiazoles 22 and 24 fail to give regiocontrolled Suzuki, Stille or Negishi couplings, however, 4-bromo-3-iodo-5-phenylisothiazole 24 gives the regiospecific palladium catalysed Ullmann-type reaction product 3,3'-bi(4-bromo-5-phenylisothiazole) 25 . Alkali hydrolysis of 3-chloro-4,5-diphenylisothiazole 8 gives the 3-hydroxy analogue 12 which is converted into 3-bromo-4,5-diphenylisothiazole 13 with POBr(3). 3-Bromoisothiazole 13 reacts with phenylzinc chloride to give 3,4,5-triphenylisothiazole 17 but fails to undergo effective Suzuki or Stille couplings. 3,5-Diphenylisothiazole-4-carbonitrile 26 is converted into the 4-bromo- and 4-iodo-3,5-diphenylisothiazoles 30 and 34 both of which are effective for Suzuki and Stille couplings. A series of triarylisothiazoles are prepared in this manner and fully characterised.

Identification of isothiazole-4-carboxamidines derivatives as a novel class of allosteric MEK1 inhibitors

The development of potent, orally bioavailable, and selective series of 5-amino-3-hydroxy-N(1-hydroxypropane-2-yl)isothiazole-4-carboxamidine inhibitors of MEK1 and MEK-2 kinase is described. Optimization of the carboxamidine and the phenoxyaniline group led to the identification of 55 which gave good potency as in vitro MEK1 inhibitors, and good oral exposure in rat.

Identification of novel, selective and potent Chk2 inhibitors

A series of isothiazole carboxamidine compounds were synthesized and discovered as novel and selective inhibitors for Chk2. They are not active against the related Chk1 kinase. The structure-activity relationship studies were performed on the scaffold, and enzymatic kinetic analysis showed they are simple ATP competitive inhibitors with K(i) values as low as 11 nM for Chk2. Computer modeling studies were employed to comprehend the mechanism of action and SAR of these compounds.