IL-2-inducible T cell kinase (ITK)

IL-2-inducible T cell kinase (ITK) is a member of the Tec family of non-receptor tyrosine kinases that plays a central role in T-cell receptor (TCR) signaling and T-cell development [1, 4]. Predominantly expressed in T lymphocytes, natural killer (NK) cells, and mast cells, ITK is recruited to the cell membrane upon TCR activation, where it interacts with the SLP-76/LAT adapter complex to phosphorylate and activate PLCγ1 [12, 16]. This activation leads to calcium mobilization and the subsequent activation of transcription factors like NFAT and NFκB, which are essential for the production of pro-inflammatory cytokines such as IL-2, IL-4, and IL-13 [1, 13, 16]. Biologically, ITK is a critical regulator of the differentiation of Th2, Th9, and Th17 cell subsets, making it a key driver in inflammatory and autoimmune conditions [1, 6]. In clinical contexts, dysregulated ITK signaling and genetic translocations, such as the ITK-SYK fusion, are implicated in the pathogenesis of T-cell malignancies, including angioimmunoblastic T-cell lymphoma and NK/T-cell lymphoma [7, 21]. Therapeutic strategies targeting ITK utilize small molecule inhibitors to modulate overactive T-cell responses in diseases like allergic asthma, rheumatoid arthritis, and psoriasis [1, 17, 20]. Current drug development includes selective covalent inhibitors like soquelitinib (CPI-818) and dual BTK/ITK inhibitors such as ibrutinib [12, 13, 16]. However, the therapeutic window is narrow, as genetic ITK deficiency in humans leads to severe CD4 lymphopenia and extreme susceptibility to Epstein-Barr virus-associated lymphoproliferative disorders [1, 2, 21].

Other names

EMTLYKPSCTK1T-cell-specific kinase (Tsk)Tyrosine-protein kinase ITK/TSK

ITK inhibitors act by binding to the ATP-binding site or allosteric pockets of the kinase domain, preventing the phosphorylation of its primary substrate, PLCγ1. This blockade interrupts T-cell receptor-mediated signaling, specifically inhibiting calcium influx and the nuclear translocation of NFAT, thereby reducing T-cell proliferation and the secretion of pro-inflammatory cytokines [1, 5, 10, 16].