Search

The aims were to develop, evaluate and apply in vitro methods for cytostatic drug sensitivity, based on intracellular concentrations found after in vivo infusions. The intracellular pharmacokinetics of anthraquinones and ara-C were compared during and after infusion to leukemic patients. Drug concentrations were evaluated with HPLC. All anthraquinones had a rapid uptake in the leukemic cells. Daunorubicin and idarubicin reached the highest levels. With lOmg/m2, the intracellular concentration of idarubicin was 70% of that of daunorubicin 50mg/m2, administered simultaneously to the same patient. Idarubicin had a more rapid initial intracellular elimination but a longer terminal retention. Doxorubicin and mitoxantrone also reached their intracellular peak levels at the end of the infusion, but the peaks were lower than those of daunorubicin and idarubicin. Both doxorubicin and mitoxantrone had a marked retention in leukemia cells. Continuous infusion of ara-C was needed to maintain adequate intracellular concentrations of the active metabolite ara-CTP. Based on these results we established in vitro incubations to reflect the in vivo intracellular concentrations of the drugs. For daunorubicin and mitoxantrone incubations during one hour at a concentration of 0.2 and 0.05myM, respectively were optimal. The corresponding conditions for doxorubicin, that is less lipid soluble were 0.211M during three hours. Ara-C, an S-phase specific drug, required a continuous incubation of 0.5myM to reach intracellular concentrations of ara-CTP mimicking those in vivo. The toxicity to leukemic cells of these incubations was tested with the DiSC-assay to gain feasible effects in vitro. For anthracyclines 60% and for ara-C 35% surviving cells were the limits that best discriminated drug resistant from sensitive cells. When both drugs were analysed together, the predictive accuracy was 91% for in vitro drug sensitivity and 92% for resistance. The probability to predict a complete remission