BIOCHEMICAL AND ANTIPROLIFERATIVE PROPERTIES OF 4-[AR(ALK)YLAMINO]PYRIDOPYRIMIDINES, A NEW CHEMICAL CLASS OF POTENT AND SPECIFIC EPIDERMAL GROWTH-FACTOR RECEPTOR TYROSINE KINASE INHIBITOR

The tyrosine kinase inhibitors PD 69896, 153717, and 158780, which bel ong to the chemical class 4-[ar(alk)ylamino] pyridopyrimidines, have b een characterized with respect to enzymelogy, target specificity, and antiproliferative effects in tumor cells. These compounds were competi tive inhibitors with respect to ATP against purified epidermal growth factor (EGF) receptor tyrosine kinase and inhibited EGF receptor autop hosphorylation in A431 human epidermoid carcinoma with IC50 values of 2085, 110, and 13 nM, respectively. Onset of inhibition was immediate once cells were exposed to these compounds, whereas recovery of recept or autophosphorylation activity after the cells were washed free of th e compound was dependent on inhibitory potency. Thus, full activity re turned immediately after removal of PD 69896 but required 8 hr after e xposure to PD 158780. PD 158780 was highly specific for the EGF recept or in Swiss 3T3 fibroblasts, inhibiting EGF-dependent receptor autopho sphorylation and thymidine incorporation at low nanomolar concentratio ns while requiring micromolar levels for platelet derived growth facto r-and basic fibroblast growth factor-dependent processes. PD 158780 in hibited heregulin-stimulated phosphorylation in the SK-BR-3 and MDA-MB 453 breast carcinomas with IC50 values of 49 and 52 nM, respectively, suggesting that the compound was active against other members of the EGF receptor family. The antiproliferative effects of this series of c ompounds against A431 cells correlated precisely with the inhibitory p otency against EGF receptor autophosphorylation. PD 158780 reduced clo ne formation in soft agar of fibroblasts transformed by EGF, EGF recep tor, or the neu oncogene but not ras or raf, further demonstrating its high degree of specificity. Finally, this compound was active against clone formation in several breast tumors having different expression patterns of the erbB family, indicating an anticancer utility in tumor s expressing these receptors. (C) 1997 Elsevier Science Inc.