Potent inhibitor of p56lck tyrosine kinase activity (IC50 = 17 nM for inhibition of autophosphorylation). Displays 7- to 20-fold selectivity over p59fyn and p60src tyrosine kinases, > 40-fold selectivity over c-ErbB2, EGF- and insulin-receptor tyrosine kinases, and > 100-fold selectivity over PKA and PKC. Mobilizes intracellular Ca2+ in dermal fibroblasts and inhibits Ras function. Also inhibits LIMK1/2, as well as migration and invasion of breast cancer cells in vitro. Purity 98%. MW (observed): 282.25