Sensitivity to the abl inhibitor STI571 in fresh leukaemic cells obtained from chronic myelogenous leukaemia patients in different stages of disease

ST1571 (CGP57148B) is an inhibitor of BCR/ABL, the cause of chronic myeloid leukaemia (CML). A difference exists between CML patients in chronic phase , in which responses to STI571 are durable, and patients in blast crisis, w ho generally experience only transient responses. Leukaemic cells from six CML patients from whom samples could be obtained during chronic phase and a t the time of blast crisis (BC) were compared for sensitivity to STI571 usi ng an in vitro assay. BC samples showed a sensitivity similar to that obtai ned during chronic phase, suggesting that no substantial intrinsic resistan ce to STI571 present in BC.