All-trans retinoic acid pharmacokinetics and bioavailability in acute promyelocytic leukemia: intracellular concentrations and biologic response relationship.

PURPOSEThis study investigated the in vitro pharmacologic behavior and disposition kinetics of all-trans retinoic acid (ATRA) in acute myeloid leukemic (AML) cells, their sensitivity to its differentiating effect, and the in vivo response of acute promyelocytic leukemia (APL) patients after therapy.PATIENTS AND METHODSFresh leukemic cells from 14 AML patients (nine APL and five non-APL), were incubated in suspension culture in the absence or presence of 10(-6) mol/L ATRA. Intracellular ATRA concentration and ATRA metabolism was determined by high-performance liquid chromatography (HPLC).RESULTSImmediate uptake is observed with maximal intracellular levels (Cmax) achieved after 24 hours of incubation. At this time, ATRA levels were variable, ranging from 20 to 230 pmol/10(6) cells (median, 100 pmol/10(6) cells). Comparison of ATRA intracellular levels with the in vitro response of patients' cell samples as measured by the percentage of nitro blue tetrazolium (NBT)-positive cells after a 3-day incubation pe...