the present invention relates to the enhancement of the efficacy of drugs , and more particularly , with overcoming the resistance of cells or organisms to drugs . in particular , the present invention provides a method for enhancing the effectiveness of a cytotoxic or anti - neoplastic agent , comprising the step of co - administering said agent with hyaluronan , wherein co - administration with hyaluronan enhances the agent &# 39 ; s cancer cell - killing potential .