HPMA Copolymer-1,5-Diazaanthraquinone Conjugates as Novel Anticancer Therapeutics

Abstract

1,5-diazaanthraquinones (DAQs) are promising anticancer drugs, however, their clinical potential is limited due to poor solubility. Conjugation of anticancer agents to hydrophilic water-soluble polymers can overcome this problem and has already been used to generate conjugates with demonstrated clinical benefit. Here a library of N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer conjugates containing a novel amino-functionalised 1,5-diazaanthraquinone derivative (amino-DAQ) have been synthesised. The conjugates were fully characterised by UV, HPLC, SEC, FT-Raman and NMR spectroscopy. Conjugation to HPMA copolymers improved amino-DAQ aqueous solubility (>7-fold). The HPMA copolymer-amino-DAQ conjugates were slightly less haemolytic than the parent compound (2% Hb released in 1 h for conjugate HPMA copolymer-GFLG (5 mol%)-amino-DAQ conjugate compared to 13% obtained with amino-DAQ). When conjugates were incubated with isolated rat liver lysosomal enzymes (Tritosomes) the rate of amino-DAQ release was influenced by both drug loading and the composition of the peptidyl side chain used to link the drug to the carrier. The higher the drug loading the lower the rate of drug release. Whereas the GG linker did not release amino-DAQ, up to 26% of the amino-DAQ was released from a GFLG linker over 24 h. The in vitro cytotoxicity of these conjugates was evaluated against two different cell lines, B16F10 murine melanoma and MCF-7 human breast cancer cells. HPMA copolymer-amino-DAQ conjugates, which are internalised by cells by the endocytic pathway, showed much lower in vitro cytotoxicity (IC50 for HPMA copolymer-GFLG (5 mol%)-amino-DAQ conjugate>397 microM drug-equiv.) than the free drug (the IC50 for amino-DAQ was 12.6 and 2.8 microM against the B16F10 murine melanoma and the MCF-7 breast cancer cell line, respectively). Nonetheless, the observed lysosomal activation of the HPMA copolymer-GFLG-amino-DAQ conjugates, suggests that evaluation of the antitumour potential in vivo is warranted.

Phase II studies of polymer-doxorubicin (PK1, FCE28068) in the treatment of breast, lung and colorectal cancer

“…This approach may be used in the future with established cytotoxics or to deliver anticancer agents that are otherwise too insoluble (26) or too toxic to be administered in the clinic (4), and conjugates can be designed to release drug with a variety of trigger mechanisms including falling pH (27)(28)(29) and reducing environment (30). The polymer carrier also permits incorporation of membrane active peptides or targeting agents into the conjugate structure, the latter designed to enhance receptor-mediated uptake into tumour cells or organs containing tumour metastases, and increase the exposure of the tumour to active drug while minimizing exposure of normal tissues (31).…”

HPMA Copolymer-Aminohexylgeldanamycin Conjugates Targeting Cell Surface Expressed GRP78 in Prostate Cancer

“…The use of drug conjugates with water-soluble polymers such as poly ethylene glycol (PEG) and N-(2-hydroxypropyl) methacrylamide (HPMA) copolymers are well suited to overcome these limitations (9,10). First, polymeric carriers can increase the water solubility of poorly water-soluble drugs (11). Second, the use of polymeric conjugates can significantly alter drug pharmacokinetics and biodistribution (12,13).…”

Polymer–drug conjugates: towards a novel approach for the treatment of endrocine-related cancer

“…ellipticines and TNP-470 (Satchi-Fainaro et al 2004)), or interesting novel natural product antitumour agents (e.g. geldanamycin derivatives (Nishiyama et al 2003), 1,5-diazaanthraquinones (Vicent et al 2004a) and wortmannin (Varticovski et al 2001)). In all cases, HPMA copolymers of traditional structure (molecular weight characteristics and a GlyPhe-Leu Gly linker) have been used as a platform, with the terminal linker dependent on compound chemistry.…”