In vivo cytotoxicity and antineoplastic activity of a transferrin-daunorubicin conjugate.

Transferrin, the major iron-binding protein in the plasma of vertebrate species, is an essential growth factor for proliferating malignant cells. The specific receptor binds diferric transferrin and is endocytosed into the cell. We would like to take advantage of this physiologic phenomenon using an active transferrin-daunorubicin conjugate to target cancer cells. We have compared the in vitro and the in vivo activity of free daunorubicin and of daunorubicin transferrin conjugate on cancer cells. The results suggest that our conjugate is less toxic and more active upon malignant cells than the free drug, daunorubicin, while being less toxic for normal cells.