2-Aminobenzimidazoles as potent ITK antagonists: trans-stilbene-like moieties targeting the kinase specificity pocket

Tautomeric and non-tautomeric N-substituted 2-iminobenzimidazolines as new lead compounds for the design of anti-influenza drugs: An in vitro study

A series of 1,3-disubstituted 2-iminobenzimidazolines as well as a number of their tautomeric analogs were synthesized. The synthesized compounds were tested for their cytotoxicity against MDCK cells and for inhibiting activity against influenza virus A/California/07/09 (H1N1)pdm09. Based on the results obtained, 50% cytotoxic concentration (CC₅₀), 50% inhibiting concentration (IC₅₀) and selectivity index (SI) were calculated for each compound. It was found that some of synthesized benzimidazole derivatives (7 of 22, 32%) possess strong virus-inhibiting activity against pandemic influenza virus (IC₅₀'s in low micromolar range) with quite moderate cytotoxicity (CC₅₀ in the range of thousands micromoles). Due to their high selectivity (highest SI's=50-83) these compounds are of significant interest for further in vivo experiments as well as for further structural optimization and drug development.

Tetrahydroindazoles as Interleukin-2 Inducible T-Cell Kinase Inhibitors. Part II. Second-Generation Analogues with Enhanced Potency, Selectivity, and Pharmacodynamic Modulation in Vivo

The medicinal chemistry community has directed considerable efforts toward the discovery of selective inhibitors of interleukin-2 inducible T-cell kinase (ITK), given its role in T-cell signaling downstream of the T-cell receptor (TCR) and the implications of this target for inflammatory disorders such as asthma. We have previously disclosed a structure- and property-guided lead optimization effort which resulted in the discovery of a new series of tetrahydroindazole-containing selective ITK inhibitors. Herein we disclose further optimization of this series that resulted in further potency improvements, reduced off-target receptor binding liabilities, and reduced cytotoxicity. Specifically, we have identified a correlation between the basicity of solubilizing elements in the ITK inhibitors and off-target antiproliferative effects, which was exploited to reduce cytotoxicity while maintaining kinase selectivity. Optimized analogues were shown to reduce IL-2 and IL-13 production in vivo following oral or intraperitoneal dosing in mice.

Property- and structure-guided discovery of a tetrahydroindazole series of interleukin-2 inducible T-cell kinase inhibitors

Interleukin-2 inducible T-cell kinase (ITK), a member of the Tec family of tyrosine kinases, plays a major role in T-cell signaling downstream of the T-cell receptor (TCR), and considerable efforts have been directed toward discovery of ITK-selective inhibitors as potential treatments of inflammatory disorders such as asthma. Using a previously disclosed indazole series of inhibitors as a starting point, and using X-ray crystallography and solubility forecast index (SFI) as guides, we evolved a series of tetrahydroindazole inhibitors with improved potency, selectivity, and pharmaceutical properties. Highlights include identification of a selectivity pocket above the ligand plane, and identification of appropriate lipophilic substituents to occupy this space. This effort culminated in identification of a potent and selective ITK inhibitor (GNE-9822) with good ADME properties in preclinical species.

Discovery and optimization of indazoles as potent and selective interleukin-2 inducible T cell kinase (ITK) inhibitors

There is evidence that small molecule inhibitors of the non-receptor tyrosine kinase ITK, a component of the T-cell receptor signaling cascade, could represent a novel asthma therapeutic class. Moreover, given the expected chronic dosing regimen of any asthma treatment, highly selective as well as potent inhibitors would be strongly preferred in any potential therapeutic. Here we report hit-to-lead optimization of a series of indazoles that demonstrate sub-nanomolar inhibitory potency against ITK with strong cellular activity and good kinase selectivity. We also elucidate the binding mode of these inhibitors by solving the X-ray crystal structures of the complexes.

Structure-based design and synthesis of potent benzothiazole inhibitors of interleukin-2 inducible T cell kinase (ITK)

Inhibition of the non-receptor tyrosine kinase ITK, a component of the T-cell receptor signalling cascade, may represent a novel treatment for allergic asthma. Here we report the structure-based optimization of a series of benzothiazole amides that demonstrate sub-nanomolar inhibitory potency against ITK with good cellular activity and kinase selectivity. We also elucidate the binding mode of these inhibitors by solving the X-ray crystal structures of several inhibitor-ITK complexes.

Inhibitors of interleukin-2 inducible T-cell kinase as potential therapeutic candidates for the treatment of various inflammatory disease conditions

Interleukin-2 inducible T-cell kinase (ITK), a member of Tec family of non-receptor protein tyrosine kinases plays a domineering role in the T-cell development, differentiation and production of pro-inflammatory cytokines such as IL-2, IL-4, IL-5, IL-10, IL-13 and IL-17. This kinase is also an important contributor in Th 2 cells mediated autoimmune and allergic disease conditions, e.g. psoriasis, atopic dermatitis and allergic asthma. ITK modulates T-cell signaling by activating PLCγ1 and regulating the extent of Ca²⁺ flux. It contributes in prolific T-cell responses by maintaining cellular adhesion and cytoskeleton reorganization via actin polymerization and integrin binding. This review article describes the structure of ITK and its role in T-cell signaling. In addition to this, data regarding small molecule inhibitors of ITK has also been reviewed from different papers and patents published.

Small-molecule protein and lipid kinase inhibitors in inflammation and specific models for their evaluation

The inflammatory response requires complex and coordinated cooperation of different signaling pathways and cell types. Therefore, more than 40 different protein or lipid kinases can be regarded as potential small-molecule inhibitor targets to approach a therapy of acute inflammation, such as septic syndrome, and especially chronic inflammation, such as rheumatoid arthritis or inflammatory bowel disease. Besides the general considerations about selectivity and potency of small-molecule kinase inhibitors, in this chapter special emphasis is put on the inflammation-specific methods and assays available for testing potential small-molecule inhibitors for their anti-inflammatory activity. Examples for human cell-based assays for characterization of the effect of inhibitors on contribution of various cell types, such as monocytes, neutrophils, mast cells, T-cells, and synovial fibroblasts, to the inflammatory scenario are given. It is further demonstrated how these assays are complemented by rodent models for septic syndrome, rheumatoid arthritis, ulcerative colitis, Crohn's disease, and systemic lupus erythematosus. Finally, it is discussed how the results obtained by these methods can be further validated and which future strategies for the treatment of chronic inflammation will exist.

A three-dimensional pharmacophore modelling of ITK inhibitors and virtual screening for novel inhibitors

Interleukin-2-inducible T-cell kinase (ITK) is a key member of the Tec family of non-receptor tyrosine kinases, and has been found to be a novel target for a number of inflammatory and autoimmune diseases. A three-dimensional pharmacophore model has been generated for protein ITK from its known inhibitors. The best HypoGen model consisted of four pharmacophore features: one hydrogen bond acceptor, one hydrogen bond donor and two hydrophobic rings. This model showed a correlation coefficient of 0.947, a root mean square deviation of 0.914 and a configuration cost of 16.866. The model was validated using test set prediction and Fischer's test. A test set containing 204 compounds showed an r(2) of 0.745 between estimated activity and activity measured experimentally. Fisher's test gave a confidence level of 95%. The best pharmacophore model (Hypo1) was then employed for virtual screening (3D database searching), including Lipinsiki's filter, to obtain a pool of more drug-like molecules. The molecular pool thus retrieved was subjected to docking analysis with a study protein to remove any molecules showing false positive activity for ITK.

An efficient new route to dihydropyranobenzimidazole inhibitors of HCV replication

A class of dihydropyranobenzimidazole inhibitors was recently discovered that acts against the hepatitis C virus (HCV) in a new way, binding to the IRES-IIa subdomain of the highly conserved 5' untranslated region of the viral RNA and thus preventing the ribosome from initiating translation. However, the reported synthesis of these compounds is lengthy and low-yielding, the intermediates are troublesome to purify, and the route is poorly structured for the creation of libraries. We report a streamlined route to this class of inhibitors in which yields are far higher and most intermediates are crystalline. In addition, a key variable side chain is introduced late in the synthesis, allowing analogs to be easily synthesized for optimization of antiviral activity.

Itk inhibitors: a patent review

Importance of field: IL-2 inducible T-cell kinase (Itk) is a non-receptor tyrosine kinase of the Tec family. It plays an important role in T cell signaling and the production of various pro-inflammatory cytokines such as IL-2, IL-4, IL-5, IL-10 and IL-13. Inhibition of Itk has been a target for the treatment of diseases related to inflammation disorders such as psoriasis and allergic asthma. Rich resources on the structural information for Itk made discovery of novel selective Itk inhibitors blossom in the past decade.

AREAS COVERED IN THIS REVIEW

In this report, distinct structural classes of specific Itk inhibitors are summarized and their in vitro/in vivo properties are discussed.

WHAT THE READER WILL GAIN

A summary of 21 patents including 16 different chemical structure classes of Itk inhibitors. The in vivo efficacies of some of the inhibitors in animal models are also discussed.

TAKE HOME MESSAGE

Although some of the inhibitors show efficacy in different animal models, which implies potential for therapeutic use in human, there is not yet a chemical entity reported in clinical trials. The prospects for Itk inhibitors will rely on the quality of the compound and the validity of the target in patients within the selected therapeutic area.