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

The N'-Substituted Derivatives of 5-Chloro-3-Methylisothiazole-4-Carboxylic Acid Hydrazide with Antiproliferative Activity

Thanks to the progress in oncology, pharmacological treatment of cancer is gaining in importance and in the near future anti-cancer chemotherapeutics are expected to be the main method of treatment for cancer diseases. What is more, the search for new anti-cancer compounds with the desired application properties is constantly underway. As a result of designed syntheses, we obtained some new N’-substituted 5-chloro-3-methylisothiazole-4-carboxylic acid hydrazide derivatives with anticancer activity. The structure of new compounds was determined by mass spectrometry (MS), elemental analysis, proton nuclear magnetic resonance spectroscopy (¹H-NMR), carbon nuclear magnetic resonance spectroscopy (¹³C-NMR), ¹H-¹³C NMR correlations and infrared spectroscopy (IR). Moreover, the structures of the compounds were confirmed by crystallographic examination. The antiproliferative MTT tests for 11 prepared compounds was conducted towards human biphenotypic B cell myelomonocytic leukemia MV4-11. SRB test was used to examine their potential anticancer activity towards human colon adenocarcinoma cell lines sensitive LoVo, resistant to doxorubicin LoVo/DX, breast adenocarcinoma MCF-7 and normal non-tumorigenic epithelial cell line derived from mammary gland MCF-10A. The most active compound was 5-chloro-3-methyl-N′-[(1E,2E)-(3-phenyloprop-2-en-1-ylidene]isothiazole-4-carbohydrazide, which showed the highest antiproliferative activity against all tested cell lines.

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.

In silico exploration for identifying structure-activity relationship of MEK inhibition and oral bioavailability for isothiazole derivatives

In this study, quantitative structure-activity/property models are developed for modeling and predicting both MEK inhibitory activity and oral bioavailability of novel isothiazole-4-carboxamidines. The models developed are thoroughly discussed to identify the key components that influence the inhibitory activity and oral bioavailability of the selected compounds. These selected descriptors serve as a first guideline for the design of novel and potent MEK inhibitors with desired ADME properties.

Human kinome drug discovery and the emerging importance of atypical allosteric inhibitors

IMPORTANCE OF THE FIELD

Protein kinases are important targets for drug discovery because they possess critical roles in many human diseases. Several protein kinase inhibitors have entered clinical development with others having already been approved for treating a host of diseases. However, many kinase inhibitors suffer from non-selectivity because they interact with the ATP binding region which has similar structures amongst the protein kinases and this non-selectivity sometimes can cause side effects. As a consequence, there is much interest in developing drugs that inhibit kinases through non-classical mechanisms with the hope of avoiding the side effects of previous kinase drugs.

AREAS COVERED IN THIS REVIEW

This review covers emerging information on kinase biology and discusses new approaches to design selective inhibitors that do not compete with ATP.

WHAT THE READER WILL GAIN

The reader will gain a better understanding of the importance of the field of allosteric inhibitor drug discovery and how this has required the adoption of a new generation of high-throughput screening techniques.

TAKE HOME MESSAGE

Discovery and development of allosteric modulators will result in a family of novel kinase therapies with greater selectivity and more varied ways to control activity of disease causing kinase targets.

Synthesis of Novel Vanillin Derivatives Containing Isothiazole Moieties and its Synergistic Effect in Mixtures with Insecticides

Reaction between 4-formyl-2-methoxyphenyl 4,5-dichloroisothiazole-3-carboxylate with various aromatic amines led to azomethins 2-7 formation. By treatment of azomethins 2-7 with sodium triacetoxyborohydride corresponding amines 8-11 were obtained. During the bioassays of new vanillin derivatives in mixtures with insecticides remarkable synergetic effect was discovered.

Allosteric modulation of kinases and GPCRs: design principles and structural diversity

Allosteric binding sites, as opposed to traditional orthosteric binding sites, offer unparalleled opportunities for drug discovery by providing high levels of selectivity, mimicking physiological conditions, affording fewer side effects because of desensitization/downregulation, and engendering ligands with chemotypes divergent from orthosteric ligands. For kinases, allosteric mechanisms described to date include alteration of protein kinase conformation blocking productive ATP binding which appear 'ATP competitive' or blocking kinase activation by conformational changes that are 'ATP non-competitive'. For GPCRs, allosteric mechanisms impart multiple modes of target modulation (positive allosteric modulation (PAM), negative allosteric modulation (NAM), neutral cooperativity, partial antagonism (PA), allosteric agonism and allosteric antagonism). Here, we review recent developments in the design principles and structural diversity of allosteric ligands for kinases and GPCRs.

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.