Evaluation of in vivo antineoplastic effects of rapamycin in patients with chemotherapy-refractory AML

BackgroundThe mammalian target of rapamycin (mTOR) has recently been identified as a potential target in acute myeloid leukemia (AML).MethodsWe treated 5 patients with chemotherapy-refractory AML with the mTOR-inhibitor rapamycin at 2 mg per os daily for 14 days, with dose adjustment allowed to reach a target serum rapamycin concentration of 10–20 ng/mL. Four of five patients received additional hydroxyurea at constant dose during treatment with rapamycin.ResultsTwo patients achieved a leukocyte response, in one of them, a prolonged response was seen. In the other patients, blast counts remained stable or increased during rapamycin therapy. We did not observe severe hematologic or non-hematologic side effects of rapamycin.ConclusionRapamycin at 2 mg per day acts mildly cytoreductive in a subgroup of patients with refractory AML. Higher doses and drug combinations may be required to obtain long lasting anti-leukemic effects in these patients.