Long-lasting memory of cellular immunity in a chronic myeloid leukemia patient maintains molecular response 5 after cessation of dasatinib

Tyrosine kinase inhibitors (TKIs), including imatinib, dasatinib and nilotinib are primarily used in the initial treatment of chronic phase (CP)-chronic myeloid leukemia (CML), as CMLs harbor the BCR-ABL fusion product. An increased number of lymphocytes and large granular lymphocytes (LGLs) have been observed in patients treated with dasatinib, but not other TKIs. The LGLs have been reported to be primarily natural killer (NK) cells and cytotoxic T lymphocytes (CTLs). In the present study, a CP-CML patient who has maintained molecular response 5 for >2.4 years after stopping dasatinib was reported. Memory and effector CTLs and NK cells, were observed after 2.4 years of treatment-free remission, despite the fact that lymphocyte counts are not elevated in the patient. These results suggest that dasatinib may induce cellular immunity, including NK cells and CTLs and this cellular immunity may be maintained for a long period following cessation of dasatinib. The results suggest that this cellular immunity may provide a long-term cure without the need for continued TKI treatment.