Pharmacodynamic and pharmacokinetic aspects of iodo-doxorubicin

Iodo-doxorubicin (I-DOX) is a new doxorubicin (DOX) analog presently in phase II clinical trials in Europe. This drug is similar to DOX in its metabolism but differs in its pharmacokinetics. We describe correlations between pharmacokinetic parameters and toxicity. There is a linear relationship between the dose in mg/m2 and the nadirs of the reduction in white blood cells (WBC), neutrophils (PMN), platelets (PLT), and hemoglobin (HB). Furthermore, a linear correlation exists between the dose in mg/m2 and the area under the curve (AUC) of I-DOX. The relationship between the AUC of I-DOX and the reduction of PMNs plotted on a logarithmic scale shows a sigmoidal curve, whereas no such correlation was found between I-doxorubicinol, the major cytostatic metabolite, and the reduction in PNMs. The variation in the AUC for I-DOX correlated with the relative amount of metabolism of I-DOX. A correlation existed between the relative amount of metabolism of I-DOX and the reduction in PNMs. These results may have an impact on the evaluation of I-DOX in phase II trials, since a sound understanding of the pharmacokinetic/pharmacodynamic relationships can yield important information for minimizing unacceptable toxicity during phase II, as well as phase III, trials.