Doxorubicin is an anthracycline antitumor antibiotic effective against a wide range of malignant tumors, although the life threating cardiac toxicity limits its long-term applications. One potential approach to overcome the cardiac toxicity of doxorubicin is to use a glucuronide prodrug (HMR 1826) from which the active drug is released by the action of β-glucuronidase, an enzyme present at high concentration in the necrotic regions of tumor (Bosslet et al., 1998). HMR 1826 has shown to possess 7-fold higher tumor selectivity index and 100 times less cardiotoxicity than doxorubicin (Murdter et al., 1997, Platel et al., 1999). However, low circulation half-life and bioconversion only at the inflammatory cell infiltration sites have restricted
