Decitabine triphosphate levels in peripheral blood mononuclear cells from patients receiving prolonged low-dose decitabine administration: a pilot study.

PURPOSE: Decitabine is a nucleoside analog used in the treatment for myelodysplastic syndrome. The compound requires intracellular conversion to its triphosphate to become active. Decitabine triphosphate has, however, never been quantified in peripheral blood mononuclear cells (PBMCs) from patients. METHOD: This article describes a method for the quantitative determination of decitabine triphosphate in PBMCs using liquid chromatography coupled to tandem mass spectrometry. The method was applied to ex vivo incubated whole blood samples and samples from three patients receiving prolonged low-dose decitabine treatment. RESULTS: We successfully quantitated decitabine triphosphate in PBMCs. Considerable levels were detected in PBMCs from two patients that responded well to therapy, whereas only low levels were present in a non-responding patient. Moreover, the data show that, in contrast to plasma decitabine, intracellular decitabine triphosphate accumulates during a treatment cycle of nine infusions at a dose of 15 mg/m(2). CONCLUSIONS: The results suggest a relationship between decitabine triphosphate levels and response to therapy. Based on the observed accumulation of decitabine triphosphate during a treatment cycle, a less intensive dose scheme could be feasible.