Safe switching from dasatinib to nilotinib after a 1-month off-drug period for persistent pleural effusion in patients with chronic myelogenous leukemia in chronic phase.

The approval of two new tyrosine kinase (TK) inhibitors, nilotinib and dasatinib, has raised the issue of cross-intolerance. Evaluating the safety of interchanging TK inhibitors is particularly important for patients who are intolerant to one medication but are considered to be sensitive to the other. Available data are limited and it is unclear whether switching between TK inhibitors is possible without an off-drug period. We present two patients with chronic myelogenous leukemia in whom, following the development of symptomatic pleural effusion, medications were safely switched from dasatinib to nilotinib after a 1-month off-drug period. The lymphocytosis and increased large granular lymphocyte count observed during dasatinib treatment also subsided after switching medications.