PMID: 24593284

Authors:

Han S, Czerwinski RM, Caspers NL, Limburg DC, Ding W, Wang H, Ohren JF, Rajamohan F, McLellan TJ, Unwalla R, Choi C, Parikh MD, Seth N, Edmonds J, Phillips C, Shakya S, Li X, Spaulding V, Hughes S, Cook A, Robinson C, Mathias JP, Navratilova I, Medley QG, Anderson DR, Kurumbail RG, Aulabaugh A

Title:

Selectively targeting an inactive conformation of IL-2-induced T cell kinase by allosteric inhibitors.

Journal:

Biochem J. 2014 Mar 4.

Abstract:

IL-2-induced T cell kinase (ITK) is a critical component of signal transduction in T cells and has a well-validated role in their proliferation, cytokine release and chemotaxis. ITK is an attractive target for the treatment of T-cell mediated inflammatory diseases. Here we describe the discovery of kinase inhibitors that preferentially bind to an allosteric pocket of ITK. The novel ITK allosteric site was characterized by NMR, surface plasmon resonance, isothermal titration calorimetry, enzymology, and X-ray crystallography. Initial screening hits bound to both the allosteric pocket and the ATP site. Successful lead optimization was achieved by improving the contribution of the allosteric component to the overall inhibition. NMR competition experiments demonstrated that the dual-site binders showed higher affinity for the allosteric site compared to the ATP site. Moreover, an optimized inhibitor displayed non-competitive inhibition with respect to ATP as shown by steady-state enzyme kinetics. The activity of the isolated kinase domain and auto-activation of the full-length enzyme were inhibited with similar potency. However, inhibition of the activated full-length enzyme was weaker, presumably because the allosteric site is altered when ITK becomes activated. An optimized lead showed exquisite kinome selectivity and is efficacious in human whole blood and proximal cell-based assays.