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

J Biol Chem. 2015 Mar 6;290(10):5960-78. doi: 10.1074/jbc.M114.614891. Epub 2015 Jan 15.


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.

Keywords: Enzyme Inhibitor; Immunology; Natural Killer Cells (NK cells); T-cell; T-cell Receptor (TCR).

MeSH terms

  • Adenosine Triphosphate / metabolism
  • Benzimidazoles / administration & dosage*
  • Binding Sites
  • Crystallography, X-Ray
  • Cysteine / chemistry
  • Cysteine / metabolism
  • Humans
  • Killer Cells, Natural / drug effects
  • Killer Cells, Natural / immunology
  • Lymphocyte Activation / drug effects
  • Lymphocyte Activation / immunology
  • Protein Kinase Inhibitors / administration & dosage*
  • Protein-Tyrosine Kinases / antagonists & inhibitors
  • Protein-Tyrosine Kinases / chemistry
  • Protein-Tyrosine Kinases / metabolism*
  • Receptors, Antigen, T-Cell / drug effects
  • Receptors, Antigen, T-Cell / metabolism
  • Signal Transduction / drug effects
  • T-Lymphocytes / drug effects*
  • T-Lymphocytes / immunology


  • Benzimidazoles
  • PRN694
  • Protein Kinase Inhibitors
  • Receptors, Antigen, T-Cell
  • Adenosine Triphosphate
  • Tec protein-tyrosine kinase
  • Protein-Tyrosine Kinases
  • emt protein-tyrosine kinase
  • Cysteine

Associated data

  • PDB/3MIY
  • PDB/3QGY
  • PDB/3V8T
  • PDB/4HCU