Imatinib mesylate has limited activity against the central nervous system involvement of Philadelphia chromosome-positive acute lymphoblastic leukaemia due to poor penetration into cerebrospinal fluid.

A 32-year-old woman with relapsed Philadelphia chromosome-positive acute lymphoblastic leukaemia was treated with imatinib mesylate (formerly STI571), a selective inhibitor of BCR/ABL tyrosine kinase. Although the initial marrow response was good and stably maintained, she subsequently relapsed with extensive infiltration of leukaemic cells into the central nervous system (CNS). After controlling her CNS disease with additional intrathecal chemotherapy, we measured the concentration of imatinib in cerebrospinal fluid (CSF) and blood simultaneously. The concentration of imatinib in CSF was about 92-fold lower than that in blood. These results suggest that imatinib poorly penetrates the blood-brain barrier and has limited activity against CNS leukaemia.