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Based on information from molecular modeling, a series of 2-aminobenzimidazoles with pyrrole moieties were designed and synthesized as ITK antagonists. Results showed that a significant improvement of intrinsic and cell-based potency was achieved. X-ray crystallographic analysis of an inhibitor complex with ITK confirmed the prediction from the de novo design that the pyrrole moiety of the inhibitor would form an additional hydrogen bonding interaction with Glu436 in the catalytic domain, and hence improve overall binding affinity of the inhibitor.

A series of novel potent benzimidazole based inhibitors of interleukin-2 T-cell kinase (Itk) were prepared. In this report, we discuss the structure-activity relationship (SAR), selectivity, and cell-based activity for the series. We also discuss the SAR associated with an X-ray structure of one of the small-molecule inhibitors bound to ITK.

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.

Interleukin-2 inducible T-cell kinase (ITK) is a member of the Tec kinase family and is involved with T-cell activation and proliferation. Due to its critical role in acting as a modulator of T-cells, ITK inhibitors could provide a novel route to anti-inflammatory therapy. This work describes the discovery of ITK inhibitors through structure-based design where high-resolution crystal structural information was used to optimize interactions within the kinase specificity pocket of the enzyme to improve both potency and selectivity.

Based on the information from molecular modeling and X-ray crystal structures, the kinase specificity pocket of ITK could be occupied upon extension of the right-hand-side of the 2-benzimidazole core of the inhibitors. 2-Aminobenzimidazoles with a trans-stilbene-like extension were designed and synthesized as novel ITK antagonists. Significant improvement on binding affinity and cellular activity were obtained through the trans-stilbene-like antagonists. Several compounds showed inhibitory activity in an IL-2 functional assay.

Previously, we reported a series of novel benzimidazole based Itk inhibitors that exhibited excellent enzymatic potency and selectivity but low microsomal stability. Employing a structure based approach a new series of inhibitors with comparable potency and selectivity to the original series and with a potential for improved microsome stability was identified.

A series of novel 5-aminomethyl-1H-benzimidazole based inhibitors of Itk were prepared. Structure–activity relationships, selectivity and cell activity are reported for this series. Compound 2, a potent and selective antagonist of Itk, inhibited anti-CD3 antibody induced IL-2 production in vivo in mice.

Benzimidazole 1 was identified as a selective inhibitor of ITK by high throughput screening. Hit-to-lead studies defined the SAR at all three substituents. Reversing the amide linkage at C6 led to 16, with a fivefold improvement of potency. This enhancement is rationalized by the conformational preference of the substituent. A model for the binding of the benzimidazoles to the ATP-binding site of ITK is proposed.