Synthesis and biological evaluation of a series of hydroxybenzylphenylamine derivatives as inhibitors of EGF receptor-associated tyrosine kinase activity.

In order to obtain non-degradable and more potent protein-tyrosine kinase inhibitors, derived from the 5-(2,5-dihydroxybenzyl)-aminosalicylates already described, we have developed a new series of 5-(2,5-dihydroxybenzyl)phenylamines. The compounds, diversely substituted on the phenyl ring by alcohol, nitrile, ether, ketone, amide and thioamide groups, were tested for their ability to inhibit epidermal growth factor (EGF) receptor-associated tyrosine kinase activity in vitro. They inhibit the phosphorylation of the peptide substrate RR-Src by the EGF receptor purified from ER 22 cells, with IC50 values in the range 0.02-0.45 microns. Several of these compounds inhibit EGF-dependent DNA synthesis in ER 22 cells with IC50 values of around 1 micron and furthermore their inhibition has been found to be specific for various protein kinases.