The specific cytotoxic effects of daunomycin conjugated to antitumor antibodies.

Daunomycin was covalently bound to immunoglobulins by periodate oxidation as described in the preceding paper. Conjugates were prepared with immunoglobulins directed against either of two mouse lymphoid tumors or with nonspecific immunoglobulins. These conjugates were tested for their toxic effects on various tumor target cells as measured either by their inhibition of RNA synthesis or by their reduction of the growth of the tumor cells after transplantation. We found that the drug preferentially affected the target cells that the antibody to which it was attached could recognize. These daunomycin-antibody conjugates are therefore sufficiently toxic and selective in their effects to be potentially useful in in vivo therapeutic studies.