N-(2-hydroxypropyl)methacrylamide copolymer-6-(3-aminopropyl)-ellipticine conjugates. Synthesis, in vitro, and preliminary in vivo evaluation

Ellipticine derivatives have potential as anticancer drugs. Their clinical use has been limited, however, by poor solubility and host toxicity. As N-( 2-hydroxypropyl)methacrylamide (HPMA) copolymer-anticancer conjugates are s howing promise in early clinical trials, a series of novel HPMA copolymer c onjugates have been prepared containing the 6-(3-aminopropyl)-ellipticine d erivative (APE, NSC176328). Drug was linked to the polymer via GFLG or GG p eptide side chains. To optimize biological behavior, HPMA copolymer-GFLG-AP E conjugates with different drug loading (total APE: 2.3-7% w/w; free APE: <0.1% w/w) were synthesized. Conjugation of APE to HPMA copolymers consider ably increased its aqueous solubility (> 10-fold). HPMA copolymer-GG-APE di d not liberate drug in the presence of isolated lysosomal enzymes (tritosom es), but HPMA copolymer-GFLG-APE released APE to a maximum of 60% after 5 h . The rate of drug release was influenced by drug loading; lower loading le d to greater release. Whereas free APE (35 mug/mL) caused significant hemol ysis (50% after 1 h), HPMA copolymer-APE conjugates were not hemolytic up t o 300 mug/mL (APE-equiv). As would be expected from its cellular pharmacoki netics, HPMA copolymer-GFLG-APE was > 75 times less cytotoxic than free dru g (IC50 similar to 0.4 mug/mL) against B16F10 melanoma in vitro. However, i n vivo when tested in mice bearing s.c. B16F10 melanoma, HPMA copolymer-GFL G-APE (1-10 mg/kg single dose, APE-equiv) given i.p. was somewhat more acti ve (highest TIC value of 143%) than free APE (1 mg/kg) (T/C = 127%). HPMA c opolymer-APE conjugates warrant further evaluation as potential anticancer agents.