New polymers with antitumor activity were synthesized by conjugating ethyl p-aminobenzoate (benzocaine) and N-hydroxy-2,3-dihydroxybenzamide (Didox) onto carboxymethylcellulose (CMC) and oxidized CMC. The biological tests ( in vitro and in vivo) for these CMC derivatives exhibited prolonged half-life in serum, accumulation in the solid tumors, and inhibition of the tumor growth. The latter effect was attributed to the permeability and retention (EPR) effect.

A new series of polyanionic polymers with antitumor activity were synthesized by conjugating ethyl 4-aminobenzoate onto a series of maleic anhydride (MA) copolymers of vinyl acetate, methyl methacrylate, and styrene. The molecular weight of these copolymers ranged from 18 ϫ 10 3 to 2 ϫ 10 5 . The in vivo and in vitro biological tests showed that the maleic anhydride synthesized copolymers exhibit prolonged half-life in serum, accumulate in K 562 erythroleukemia solid tumors, and inhibit tumor growth. The antitumor activity appears to be increased by the enhanced permeability and retention (EPR) effect which is related to the macromolecular size of the antitumor agent.