Hit-to-lead studies on benzimidazole inhibitors of ITK: discovery of a novel class of kinase inhibitors

Synthesis, Computational Analysis, and Antiproliferative Activity of Novel Benzimidazole Acrylonitriles as Tubulin Polymerization Inhibitors: Part 2

We used classical linear and microwave-assisted synthesis methods to prepare novel N-substituted, benzimidazole-derived acrylonitriles with antiproliferative activity against several cancer cells in vitro. The most potent systems showed pronounced activity against all tested hematological cancer cell lines, with favorable selectivity towards normal cells. The selection of lead compounds was also tested in vitro for tubulin polymerization inhibition as a possible mechanism of biological action. A combination of docking and molecular dynamics simulations confirmed the suitability of the employed organic skeleton for the design of antitumor drugs and demonstrated that their biological activity relies on binding to the colchicine binding site in tubulin. In addition, it also underlined that higher tubulin affinities are linked with (i) bulkier alkyl and aryl moieties on the benzimidazole nitrogen and (ii) electron-donating substituents on the phenyl group that allow deeper entrance into the hydrophobic pocket within the tubulin's β-subunit, consisting of Leu255, Leu248, Met259, Ala354, and Ile378 residues.

Recent Progress of Benzimidazole Hybrids for Anticancer Potential

This review presents the detailed account of factors leading to cancer and design strategy for the synthesis of benzimidazole derivatives as anticancer agents. The recent survey for cancer treatment in Cancer facts and figures 2017 American Chemical Society has shown progressive development in fighting cancer. Researchers all over the world in both developed and developing countries are in a continuous effort to tackle this serious concern. Benzimidazole and its derivatives showed a broad range of biological activities due to their resemblance with naturally occurring nitrogenous base i.e. purine. The review discussed benzimidazole derivatives showing anticancer properties through a different mechanism viz. intercalation, alkylating agents, topoisomerases, DHFR enzymes, and tubulin inhibitors. Benzimidazole derivatives act through a different mechanism and the substituents reported from the earlier and recent research articles are prerequisites for the synthesis of targeted based benzimidazole derivatives as anticancer agents. The review focuses on an easy comparison of the substituent essential for potency and selectivity through SAR presented in figures. This will further provide a better outlook or fulfills the challenges faced in the development of novel benzimidazole derivatives as anticancer.

Role of the IL-2 inducible tyrosine kinase ITK and its inhibitors in disease pathogenesis

ITK (IL-2-inducible tyrosine kinase) belongs to the Tec family kinases and is mainly expressed in T cells. It is involved in TCR signalling events driving processes like T cell development as well as Th2, Th9 and Th17 responses thereby controlling the expression of pro-inflammatory cytokines. Studies have shown that ITK is involved in the pathogenesis of autoimmune diseases as well as in carcinogenesis. The loss of ITK or its activity either by mutation or by the use of inhibitors led to a beneficial outcome in experimental models of asthma, inflammatory bowel disease and multiple sclerosis among others. In humans, biallelic mutations in the ITK gene locus result in a monogenetic disorder leading to T cell dysfunction; in consequence, mainly EBV infections can lead to severe immune dysregulation evident by lymphoproliferation, lymphoma and hemophagocytic lymphohistiocytosis. Furthermore, patients who suffer from angioimmunoblastic T cell lymphoma have been found to express significantly more ITK. These findings put ITK in the strong focus as a target for drug development.

IL-2 Inducible Kinase ITK is Critical for HIV-1 Infection of Jurkat T-cells

Successful replication of Human immunodeficiency virus (HIV)-1 depends on the expression of various cellular host factors, such as the interleukin-2 inducible T-cell kinase (ITK), a member of the protein family of TEC-tyrosine kinases. ITK is selectively expressed in T-cells and coordinates signaling pathways downstream of the T-cell receptor and chemokine receptors, including PLC-1 activation, Ca²⁺-release, transcription factor mobilization, and actin rearrangements. The exact role of ITK during HIV-1 infection is still unknown. We analyzed the function of ITK during HIV-1 replication and showed that attachment, fusion of virions with the cell membrane and entry into Jurkat T-cells was inhibited when ITK was knocked down. In contrast, reverse transcription and provirus expression were not affected by ITK deficiency. Inhibited ITK expression did not affect the CXCR4 receptor on the cell surface, whereas CD4 and LFA-1 integrin levels were slightly enhanced in ITK knockdown cells and heparan sulfate (HS) expression was completely abolished in ITK depleted T-cells. However, neither HS expression nor other attachment factors could explain the impaired HIV-1 binding to ITK-deficient cells, which suggests that a more complex cellular process is influenced by ITK or that not yet discovered molecules contribute to restriction of HIV-1 binding and entry.

Design, synthesis, and evaluation of new α-aminonitrile-based benzimidazole biomolecules as potent antimicrobial and antitubercular agents

The study explores the one-pot synthesis of novel α-aminonitriles by reacting 4-[(1H-benzimidazol-2-yl)methoxy]benzaldehyde, substituted anilines and sodium cyanide using a catalytic amount of copper dipyridine dichloride (CuPy₂ Cl₂ ) and employing the Strecker reaction under mild conditions. All the synthesized compounds were screened for antimicrobial and antitubercular activity. The promising lead compounds 4d and 4e were identified, with MIC values ranging between 3.9 and 7.8 µg/mL against different bacterial strains. Compounds 4c-e and 4g also showed good antifungal activities against the tested fungal strain. Among those tested, compound 4e exhibited excellent antitubercular activity (MIC 0.05 μg/mL) with a low level of cytotoxicity, suggesting that compound 4e is a promising lead for subsequent investigations in search for new antitubercular agents.

Atom and receptor based 3D QSAR models for generating new conformations from pyrazolopyrimidine as IL-2 inducible tyrosine kinase inhibitors

In the current study, quantitative three-dimensional structure-activity-relationship (3D-QSAR) method was performed to design a model for new chemical entities by utilizing pyrazolopyrimidines. Their inhibiting activity on receptor IL-2 Itk correlates descriptors based on topology and hydrophobicity. The best model developed by ligand-based (atom-based) approach has correlation-coefficient of r²: 0.987 and cross-validated squared correlation-coefficient of q²: 0.541 with an external prediction capability of r²: 0.944. Whereas the best selected model developed by structured-based (receptor-based) approach has correlation-coefficient of r²: 0.987, cross-validated squared correlation-coefficient of q²: 0.637 with an external predictive ability of r²: 0.941. The statistical parameters prove that structure-based gave a better model to design new chemical scaffolds. The results achieved indicated that hydrophobicity at R₁ location play a vital role in the inhibitory activity and introduction of appropriately bulky and strongly hydrophobic-groups at position 3 of the terminal phenyl-group which is highly significant to enhance the activity. Six new pyrazolopyrimidine derivatives were designed. Docking simulation study was carried out and their inhibitory activity was predicted by the best structure based model with predictive activity of ranging from 8.43 to 8.85 log unit. The interacting residues PHE435, ASP500, LYS391, GLU436, MET438, CYS442, ILE369, VAL377 of PDB 4HCT were studied with respect to type of bonding with the new compounds. This study was aimed to search out more potent inhibitors of IL-2 Itk.

A Small Molecule Inhibitor of ITK and RLK Impairs Th1 Differentiation and Prevents Colitis Disease Progression

In T cells, the Tec kinases IL-2-inducible T cell kinase (ITK) and resting lymphocyte kinase (RLK) are activated by TCR stimulation and are required for optimal downstream signaling. Studies of CD4(+) T cells from Itk(-/-) and Itk(-/-)Rlk(-/-) mice have indicated differential roles of ITK and RLK in Th1, Th2, and Th17 differentiation and cytokine production. However, these findings are confounded by the complex T cell developmental defects in these mice. In this study, we examine the consequences of ITK and RLK inhibition using a highly selective and potent small molecule covalent inhibitor PRN694. In vitro Th polarization experiments indicate that PRN694 is a potent inhibitor of Th1 and Th17 differentiation and cytokine production. Using a T cell adoptive transfer model of colitis, we find that in vivo administration of PRN694 markedly reduces disease progression, T cell infiltration into the intestinal lamina propria, and IFN-γ production by colitogenic CD4(+) T cells. Consistent with these findings, Th1 and Th17 cells differentiated in the presence of PRN694 show reduced P-selectin binding and impaired migration to CXCL11 and CCL20, respectively. Taken together, these data indicate that ITK plus RLK inhibition may have therapeutic potential in Th1-mediated inflammatory diseases.

Rapid Vortex Fluidics: Continuous Flow Synthesis of Amides and Local Anesthetic Lidocaine

Thin film flow chemistry using a vortex fluidic device (VFD) is effective in the scalable acylation of amines under shear, with the yields of the amides dramatically enhanced relative to traditional batch techniques. The optimized monophasic flow conditions are effective in ≤80 seconds at room temperature, enabling access to structurally diverse amides, functionalized amino acids and substituted ureas on multigram scales. Amide synthesis under flow was also extended to a total synthesis of local anesthetic lidocaine, with sequential reactions carried out in two serially linked VFD units. The synthesis could also be executed in a single VFD, in which the tandem reactions involve reagent delivery at different positions along the rapidly rotating tube with in situ solvent replacement, as a molecular assembly line process. This further highlights the versatility of the VFD in organic synthesis, as does the finding of a remarkably efficient debenzylation of p-methoxybenzyl amines.

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.

Targeting interleukin-2-inducible T-cell kinase (ITK) and resting lymphocyte kinase (RLK) using a novel covalent inhibitor PRN694

Interleukin-2-inducible T-cell kinase (ITK) and resting lymphocyte kinase (RLK or TXK) are essential mediators of intracellular signaling in both normal and neoplastic T-cells and natural killer (NK) cells. Thus, ITK and RLK inhibitors have therapeutic potential in a number of human autoimmune, inflammatory, and malignant diseases. Here we describe a novel ITK/RLK inhibitor, PRN694, which covalently binds to cysteine residues 442 of ITK and 350 of RLK and blocks kinase activity. Molecular modeling was utilized to design molecules that interact with cysteine while binding to the ATP binding site in the kinase domain. PRN694 exhibits extended target residence time on ITK and RLK and is highly selective for a subset of the TEC kinase family. In vitro cellular assays confirm that PRN694 prevents T-cell receptor- and Fc receptor-induced cellular and molecular activation, inhibits T-cell receptor-induced T-cell proliferation, and blocks proinflammatory cytokine release as well as activation of Th17 cells. Ex vivo assays demonstrate inhibitory activity against T-cell prolymphocytic leukemia cells, and in vivo assays demonstrate durable pharmacodynamic effects on ITK, which reduces an oxazolone-induced delayed type hypersensitivity reaction. These data indicate that PRN694 is a highly selective and potent covalent inhibitor of ITK and RLK, and its extended target residence time enables durable attenuation of effector cells in vitro and in vivo. The results from this study highlight potential applications of this dual inhibitor for the treatment of T-cell- or NK cell-mediated inflammatory, autoimmune, and malignant diseases.

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.

Targeting Interleukin-2-Inducible T-cell Kinase (ITK) in T-Cell Related Diseases

IL2-inducible T-cell kinase (ITK), a member of the Tec family tyrosine kinases, is the predominant Tec kinase in T cells and natural killer (NK) cells mediating T cell receptor (TCR) and Fc receptor (Fc R) initiated signal transduction. ITK deficiency results in impaired T and NK cell functions, leading to various disorders including malignancies, inflammation, and autoimmune diseases. In this mini-review, the role of ITK in T cell signaling and the development of small molecule inhibitors of ITK for the treatment of T-cell related disorders is examined.

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.

Synthesis, single crystal and antitumor activities of benzimidazole-quinazoline hybrids

A series of novel regioisomeric hybrids of quinazoline/benzimidazole viz. (3-allyl-2-methyl-3H-benzimidazol-5-yl)-(2-substituted-quinazolin-4-yl)-amine and (1-allyl-2-methyl-1H-benzimidazol-5-yl)-(2-substituted-quinazolin-4-yl)-amine of biological interest were synthesized. All the synthesized compounds were well characterized by (1)H and (13)C NMR as well as mass spectroscopy. The newly synthesized compounds were screened for in vitro antitumor activities against 60 tumor cell lines panel assay. A significant inhibition for cancer cells were observed with compound 9 and also more active against known drug 5-fluorouracil (5-FU) in some tumor cell lines. Compound 9 displayed appreciable anticancer activity against leukemia, colon, melanoma, renal and breast cancer cell lines.

Synthesis and Antimicrobial Activity of Some [1,2,4]-Triazole Derivatives

A series of novel [1,2,4]-triazolo piperidine (8), [1,2,4]-triazolo piperazine (9a-c), [1,2,4]-triazolo phenylether (10a-e), and [1,2,4]-triazolo aniline (11a-c) derivatives have been synthesized. The chemical structures of the newly synthesized compounds were characterized by IR,1H NMR,13C NMR, and LCMS. The newly synthesized compounds were screened for antimicrobial activity. Among all the compounds tested,11b(R4=4-MeO–) showed the highest activity againstStaphylococcus aureusandEscherichia coli, and9a(R1andR2=Cl) showed the highest activity againstPseudomonas aeruginosa.

Preparation of Newα-Aminophosphonate Derivatives by Kabachnik-Fields Reaction Using a Recyclable Catalyst

A convenient and efficient synthetic method for the preparation of some newα-aminophosphonate derivatives via a one-pot three-component system has been achieved using Amberlite IRC-748 as a recyclable catalyst. This method not only provides an excellent complement for the synthesis ofα-aminophosphonates but also avoids the use of hazardous acids or expensive/toxic Lewis acids and harsh reaction conditions. Most of the synthesized compounds (4a–o) exhibited activity against bacteria/fungi strains and moderate DPPH radical scavenging activity.

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.

Synthesis of terphenyl benzimidazoles as tubulin polymerization inhibitors

A series of new terphenyl benzimidazoles (3a-z and 3aa-ad) were synthesized and evaluated for their anticancer activity. All the 30 compounds have shown moderate to good anticancer potency, however some of the compounds (3j, 3m-t and 3aa-ad) exhibited prominent anticancer potency with GI(50) values ranging from <0.1 to 9.72 μM. These compounds exhibit G2/M phase arrest and the analysis of tubulin by Western blot experiments in case of 3t and 3ad shows the disturbances that are caused in the ratio of soluble versus polymerized tubulin in cells. Compounds 3t and 3ad are the most promising candidates amongst the series and has the potential to be taken up for further detailed studies either alone or in combination with the existing therapies.

TEC and MAPK Kinase Signalling Pathways in T helper (TH) cell Development, TH2 Differentiation and Allergic Asthma

Significant advances in our understanding of the signalling events during T cell development and differentiation have been made in the past few decades. It is clear that ligation of the T cell receptor (TCR) triggers a series of proximal signalling cascades regulated by an array of protein kinases. These orchestrated and highly regulated series of events, with differential requirements of particular kinases, highlight the disparities between αβ+CD4+ T cells. Throughout this review we summarise both new and old studies, highlighting the role of Tec and MAPK in T cell development and differentiation with particular focus on T helper 2 (TH2) cells. Finally, as the allergy epidemic continues, we feature the role played by TH2 cells in the development of allergy and provide a brief update on promising kinase inhibitors that have been tested in vitro, in pre-clinical disease models in vivo and into clinical studies.

Structure and function of Tec family kinase Itk

Itk is a member of the Tec family of kinases that is expressed predominantly in T cells. Itk regulates the T cell receptor signaling pathway to modulate T cell development and T helper cell differentiation, particularly Th2 differentiation. Itk is also important for the development and function of iNKT cells. In this review we discuss current progress on our understanding of the structure, activation and signaling pathway of Itk, in addition to inhibitors that have been developed, which target this kinase. We also place in context the function of Itk, available inhibitors and potential use in treating disease.

Inhibition of the IL-2-inducible tyrosine kinase (Itk) activity: a new concept for the therapy of inflammatory skin diseases

T-cell-mediated processes play an essential role in the pathogenesis of several inflammatory skin diseases such as atopic dermatitis, allergic contact dermatitis and psoriasis. The aim of this study was to investigate the role of the IL-2-inducible tyrosine kinase (Itk), an enzyme acting downstream of the T-cell receptor (TCR), in T-cell-dependent skin inflammation using three approaches. Itk knockout mice display significantly reduced inflammatory symptoms in mouse models of acute and subacute contact hypersensitivity (CHS) reactions. Systemic administration of a novel small molecule Itk inhibitor, Compound 44, created by chemical optimization of an initial high-throughput screening hit, inhibited Itk's activity with an IC50 in the nanomolar range. Compound 44 substantially reduced proinflammatory immune responses in vitro and in vivo after systemic administration in two acute CHS models. In addition, our data reveal that human Itk, comparable to its murine homologue, is expressed mainly in T cells and is increased in lesional skin from patients with atopic dermatitis and allergic contact dermatitis. Finally, silencing of Itk by RNA interference in primary human T cells efficiently blocks TCR-induced lymphokine secretion. In conclusion, Itk represents an interesting new target for the therapy of T-cell-mediated inflammatory skin diseases.

Discovery and structure-activity relationship of 3-aminopyrid-2-ones as potent and selective interleukin-2 inducible T-cell kinase (Itk) inhibitors

Interleukin-2 inducible T-cell kinase (Itk) plays a role in T-cell functions, and its inhibition potentially represents an attractive intervention point to treat autoimmune and allergic diseases. Herein we describe the discovery of a series of potent and selective novel inhibitors of Itk. These inhibitors were identified by structure-based design, starting from a fragment generated de novo, the 3-aminopyrid-2-one motif. Functionalization of the 3-amino group enabled rapid enhancement of the inhibitory activity against Itk, while introduction of a substituted heteroaromatic ring in position 5 of the pyridone fragment was key to achieving optimal selectivity over related kinases. A careful analysis of the hydration patterns in the kinase active site was necessary to fully explain the observed selectivity profile. The best molecule prepared in this optimization campaign, 7v, inhibits Itk with a K(i) of 7 nM and has a good selectivity profile across kinases.

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.

Ethyl 1-sec-butyl-2-(4-chloro-phen-yl)-1H-benzimidazole-5-carboxyl-ate

In the title compound, C(20)H(21)ClN(2)O(2), the ethyl 1H-benzimidazole-5-carboxyl-ate ring system, excluding the methyl-ene and methyl H atoms, is almost planar, with a maximum deviation of 0.055 (1) Å, and makes a dihedral angle of 40.63 (4)° with the benzene ring. The sec-butyl group is disordered over two positions, with refined site occupancies of 0.855 (4) and 0.145 (4). In the crystal, mol-ecules are linked into chains along [010] via inter-molecular C-H⋯O hydrogen bonds and are further inter-connected by C-H⋯Cl inter-actions into two-dimensional networks parallel to (001). The crystal structure is further consolidated by C-H⋯π inter-actions.

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.

Ethyl 1-sec-butyl-2-(2-hydroxy-phen-yl)-1H-benzimidazole-5-carboxyl-ate 0.25-hydrate

In the title compound, C(20)H(22)N(2)O(3)·0.25H(2)O, the water mol-ecule (occupancy 0.25) is disordered across a crystallographic inversion center. The dihedral angle between the hydroxy-phenyl ring and the benzimidazole ring system is 59.31 (9)°. In the crystal structure, mol-ecules are connected by inter-molecular O-H⋯N and C-H⋯O hydrogen bonds. The crystal structure is further stabilized by a weak C-H⋯π inter-action involving the imidazole ring.

ITK inhibitors in inflammation and immune-mediated disorders

Interleukin-2-inducible T cell kinase (ITK) is a non-receptor tyrosine kinase expressed in T cells, NKT cells and mast cells which plays a crucial role in regulating the T cell receptor (TCR), CD28, CD2, chemokine receptor CXCR4, and FcepsilonR-mediated signaling pathways. In T cells, ITK is an important mediator for actin reorganization, activation of PLCgamma, mobilization of calcium, and activation of the NFAT transcription factor. ITK plays an important role in the secretion of IL-2, but more critically, also has a pivotal role in the secretion of Th2 cytokines, IL-4, IL-5 and IL-13. As such, ITK has been shown to regulate the development of effective Th2 response during allergic asthma as well as infections of parasitic worms. This ability of ITK to regulate Th2 responses, along with its pattern of expression, has led to the proposal that it would represent an excellent target for Th2-mediated inflammation. We discuss here the possibilities and pitfalls of targeting ITK for inflammatory disorders.

Tec kinases regulate T-lymphocyte development and function: new insights into the roles of Itk and Rlk/Txk

The Tec (tyrosine kinase expressed in hepatocellular carcinoma) family of non-receptor tyrosine kinases consists of five members: Tec, Bruton's tyrosine kinase (Btk), inducible T-cell kinase (Itk), resting lymphocyte kinase (Rlk/Txk), and bone marrow-expressed kinase (Bmx/Etk). Although their functions are probably best understood in antigen receptor signaling, where they participate in the phosphorylation and regulation of phospholipase C-gamma (PLC-gamma), it is now appreciated that these kinases contribute to signaling from many receptors and that they participate in multiple downstream pathways, including regulation of the actin cytoskeleton. In T cells, three Tec kinases are expressed, Itk, Rlk/Txk, and Tec. Itk is expressed at highest amounts and plays the major role in regulating signaling from the T-cell receptor. Recent studies provide evidence that these kinases contribute to multiple aspects of T-cell biology and have unique roles in T-cell development that have revealed new insight into the regulation of conventional and innate T-cell development. We review new findings on the Tec kinases with a focus on their roles in T-cell development and mature T-cell differentiation.

5-Aminomethylbenzimidazoles as potent ITK antagonists

Benzamide 1 demonstrated good potency as a selective ITK inhibitor, however the amide moiety was found to be hydrolytically labile in vivo, resulting in low oral exposure and the generation of mutagenic aromatic amine metabolites. Replacing the benzamide with a benzylamine linker not only addressed the toxicity issue, but also improved the cellular and functional potency as well as the drug-like properties. SAR studies around the benzylamines and the identification of 10n and 10o as excellent tools for proof-of-concept studies are described.