Quantitation of 1-β-d-arabinofuranosylcytosine 5́-triphosphate in the leukemic cells from bone marrow and peripheral blood of patients receiving 1-β-d-arabinofuranosylcytosine therapy

A method for the detection and quantitation of 1-β-D-arabi-nofuranosylcytosine 5́-triphosphate (ara-CTP), the active metabolite of 1-β-D-arabinofuranosylcytosine (ara-C), in the bone marrow cells and leukemic cells of the peripheral blood from patients receiving ara-C therapy is described. ara-CTP is separated from normal cellular nucleotides by high-pressure liquid chromatography and is quantitated by its absorbance of ultraviolet light at 280 nm with a lower limit of sensitivity of 25 pmol/2 × 10⁷ cell equivalents. During separate courses of continuous infusion of different therapeutic doses of ara-C, ara-CTP accumulated in the leukemic bone marrow cells of a patient with acute myelogenous leukemia in proportion to the dose of ara-C. Continuous infusion of ara-C(90 mg/sq m/day) resulted in plateau levels of ara-CTP in peripheral blast cells after 24 hr (115 pmol/1 × 10⁷ cell equivalents). A priming dose of ara-C(125 to 250 mg/sq m) followed by a 1-hr infusion of an equal dose of ara-C to patients with acute myelogenous leukemia facilitated the determination of ara-CTP retention in bone marrow and peripheral blood leukemic cells in vivo. This procedure should be useful for extended studies of the biochemical pharmacology of ara-CTP in vivo.