Lymphocyte-speci?c protein tyrosine kinase (Lck) is a member of the Src-family of non-receptor protein tyrosine kinases and plays a critical role in the initial steps of T cell receptor signaling that trigger the production of cytokines. Lck inhibitor is a pyrrolopyrimidine that blocks the activity of two forms of Lck kinase, Lck (64-509) and Lckcd, with IC50 values of <1 and 2 nM, respectively. It inhibits the related kinases Src, Kdr, and Tie-2 with much weaker potency (IC50s = 70 nM, 1.57, and 1.98 μM, respectively) and only minimally inhibits the activities of EGFR, PKC, CDC2/B and ZAP-70 (IC50s = 3.2, >33, >50, and >50 μM, respectively). This compound has been shown to inhibit T cell receptor-stimulated IL-2 production in mice (ED50s = 4 and 25 mg/kg when administered either i.p. or orally).
