Current status of ABL tyrosine kinase inhibitors stop studies for chronic myeloid leukemia.

ABL tyrosine kinase inhibitors (TKIs) dramatically improves chronic myeloid leukemia (CML) prognosis and most CML patients are now able to lead lives that are equivalent to those of healthy individuals. However, high cost to CML patients of long-term treatment and adverse effects (AEs) remain problems. At the setout, a clinical study involving the discontinuation of imatinib was conducted in France. Then, several stop studies of first-generation (imatinib) and second-generation ABL TKIs (dasatinib, nilotinib), which induce earlier response than imatinib, have also been started. These studies revealed that almost half of CML patients who are treated with ABL TKIs and achieve a certain period of sustained deep molecular response can stop ABL TKIs safely and obtain treatment free remission (TFR). AEs of ABL TKIs withdrawal and predicting factors for successful discontinuation including immunity are becoming clear gradually through these studies. It is important to conduct a comprehensive examination of the results of studies with a wide variety of protocols in order to determine which discontinuation method results in the highest probability of TFR in clinical settings.