This pyridopyrimidine (FWfree-base = 429.28 g/mol) inhibits Bcr-Abl proteintyrosine kinase and induces apoptosis of K562 leukemic cells. In vitro, PD180970 potently inhibited p210Bcr-Abl autophosphorylation (IC50 = 5 nM) as well as the kinase activity of purified Abl tyrosine kinase (IC50 = 2.2 nM). Incubation of K562 cells with PD180970 resulted in cell death, with results of nuclear staining, apoptotic-specific poly(ADP-ribose) polymerase cleavage, and annexin V binding assays confirming as much. Significantly, PD180970 is without effect on the growth and viability of p210Bcr-Ablnegative HL60 human leukemic cells. Such findings demonstrate that PD180970 is among the most potent known inhibitors of the p210Bcr-Abl tyrosine kinase and that it is a promising candidate as a novel therapeutic agent for Bcr-Abl-positive leukemia
