The anticancer agent adriamycin can be actively cytotoxic without entering cells.

The antineoplastic agent adriamycin was coupled to an insoluble agarose support. This material was actively cytotoxic to L1210 cells in culture under conditions in which no free adriamycin could enter the cell. It is concluded that an agent whose principal target was previously thought to be DNA can exert its cytotoxic action solely by interaction at the cell surface.