Synthesis of HPMA copolymer containing adriamycin bound via an acid-labilespacer and its activity toward human ovarian carcinoma cells

N-(2-Hydroxypropyl)methacrylamide (HPMA) copolymer-adriamycin (ADR) conjuga te (P-aconityl-ADR) was synthesized by the attachment of cis-aconityl-ADR t o an HPMA copolymer precursor using 1-ethyl-3-(3-dimethylaminopropyl)carbod iimide (EDC) as the condensing agent. The ADR release from the HPMA copolym er conjugate was pH sensitive. After 48 h incubation at pH 5, 6, and 7, the amount of ADR released was 63.4, 9.2, and 2.8% respectively. The in vitro cytotoxicity of time conjugate was evaluated toward A2780 sensitive and A27 80/AD resistant human ovarian carcinoma cells. An HPMA copolymer, containin g ADR bound via a tetrapeptide (GFLG) sequence susceptible to cleavage cata lyzed by lysosomal enzymes (P-GFLG-ADR), was used as control. The IC50 dose s seemed to indicate that the total hydrolysis of P-aconityl-ADR in prelyso somal and lysosomal compartments proceeded faster than the release of ADR f rom P-GFLG-ADR catalyzed by lysomal cysteine proteinases. Both HPMA copolym er-ADR conjugates appeared to overcome the ATP-driven P-glycoprotein efflux pump expressed in A2780/AD cells.