Mice afflicted with the CML-like illness demonstrate a heterogeneous hematologic response to STI571.

Animals reconstituted with BM cells transduced with a replication-defective P210^BCR/ABL retrovirus were started on treatment with STI571 beginning on day 10 after BM reconstitution. Serial peripheral blood counts were obtained at the indicated days. For comparison, blood counts from mice no. 1C and no. 3B, which failed to respond to STI571 and ultimately died from the CML-like illness, are shown at left.