ESTIMATION OF THE CHEMOSENSITIZING ACTIVITY OF MODULATORS OF MULTIDRUG-RESISTANCE VIA COMBINED SIMULTANEOUS ANALYSIS OF SIGMOIDAL DOSE-RESPONSE CURVES

The potency of modulators which re-establish sensitivity of resistant tumour cells to cytotoxic drugs is not usually described by ED50 value s, even though such values are needed for comparison of modulator acti vity. Various methods are reported for the determination of ED50 value s of propafenone-type modulators of multi-drug resistance in cytotoxic ity assays. Best results were obtained by using a combined simultaneou s analysis of dose-response curve families. This approach enables calc ulation of statistically highly significant ED50 values without any da ta reduction directly from the original data points obtained in daunom ycin cytotoxicity assays. The method also enables extrapolation of the ED50 values of compounds with low activity or poor solubility, or bot h.