A novel doxorubicin-glucuronide prodrug DOX-GA3 for tumour-selective chemotherapy: distribution and efficacy in experimental human ovarian cancer

Abstract

Doxorubicin (DOX) is an anticancer agent with a wide spectrum of activity. Cumulative dose-related cardiotoxicity, however, is a major side-effect of DOX, in addition to the acute toxicities, such as myelosuppression, nausea and vomiting. The success of DOX, and its limitations in clinical use, have directed research endeavours for the development of analogues of DOX with an improved therapeutic index. Among these are iododoxorubicin, AD-32 and epidoxorubicin (Weiss, 1992). Iododoxorubicin was noted to be promising in phase I trials, but in phase II trials the response rate was too low to warrant further development. AD-32 has greater anti-tumour activity, and less cardiotoxicity, than DOX, but drug formulation and solubility problems prevented its further clinical development. Of the available analogues, only epidoxorubicin appears to have a reduced cardiotoxicity with retention of antitumour activity and is in use in current cancer chemotherapy.Another way to improve the selectivity and efficacy of chemotherapy is the use of non-toxic prodrugs that are preferentially converted into active anticancer agents at the tumour site (Sinhababu and Thakker, 1996). N-L-leucyl-DOX is a prodrug of DOX, to be activated by tumour peptidases (Deprez-de Campeneere et al, 1982). In human ovarian cancer xenografts, N-L-leucyl-DOX was more effective than DOX . Clinical studies on N-L-leucyl-DOX, however, have indicated premature activation of the prodrug in the circulation, because of which the selectivity of the prodrug would be reduced . Elevated enzyme levels in tumour tissue have been reported for β-glucuronidase (Connors and Whisson, 1966). Bosslet et al (1995) and Schumacher et al (1996) have shown that this enzyme is released in the extracellular space as a result of necrosis in tumours. The enzyme can only be detected in very low concentrations in the circulation (Fishman, 1970). Therefore, β-glucuronidase may be exploited for the specific activation of glucuronide prodrugs in tumour tissue.We have developed glucuronide derivatives of anthracyclines and showed that these prodrugs, such as epirubicin-glucuronide (Haisma et al, 1992) and daunorubicin-glucuronides (Leenders et al, 1995;Houba et al, 1996), are relatively non-toxic in vitro and can be activated by β-glucuronidase to yield the active anthracycline. Treatment with the glucuronide prodrug daunorubicin-GA3 (DNR-GA3) induced a better tumour growth delay than daunorubicin (DNR) when studied at equitoxic doses in 3 human ovarian cancer xenografts which were sensitive to DNR (Houba et al, 1998). Comparison of the distribution and pharmacokinetics of DNR and DNR-GA3 demonstrated that the prodrug DNR-GA3 was selectively activated by human β-glucuronidase present in the tumours and resulted in a higher DNR AUC in tumours and lower A novel doxorubicin-glucuronide prodrug DOX-GA3 for tumour-selective chemotherapy: distribution and efficacy in experimental human ovarian cancer Summary The doxorubicin (DOX) prodrug N-[4-doxorubicin-N-carbonyl (oxymethyl) phenyl] O-β-glucuro...

A fully human anti-Ep-CAM scFv-beta-glucuronidase fusion protein for selective chemotherapy with a glucuronide prodrug

“…Under the experimental conditions used, the IC 50 value for doxorubicin in OVCAR-3 cells was 5 mM, which confirmed the 2.5 mM value calculated in a previous experiment (Houba et al, 2001a). This relatively high IC 50 value could probably be explained by the use of U-bottom wells, in which the cells do not grow as a monolayer, but more like a spheroid.…”

“…Therefore, DOX-GA3 is not available for conversion by the endogenous enzyme under normal circumstances. An additional advantage of this human enzyme is the fact that, in larger tumours, the glucuronyl-doxorubicin prodrug has an inhibiting effect on tumour growth on its own (Bosslet et al, 1995;Houba et al, 2001a). The success of the glucuronyl-doxorubicin prodrug is ascribed to release of the enzyme from necrotic tumour cells and macrophages in larger tumours (Bosslet et al, 1998).…”

Enhancement of CPT-11 antitumor activity by adenovirus-mediated expression of β–glucuronidase in tumors

“…anthracyclines and topoisomerase I inhibitors in mice bearing human xenografts 16,17,42 and suggests that even without Ad.bG transduction of cancer cells, SN-38 generated by deconjugation of SN-38G by bG in the tumor microenvironment may contribute to the antitumor activity of CPT-11. 45,46 Our study suggests several potential methods to further enhance the antitumor efficacy of CPT-11.…”

“…14,15 Glucuronide analogs of anticancer drugs can act as prodrugs that can be activated by the enzyme b-glucuronidase (bG). 16,17 This suggests that another approach to enhance CPT-11 effectiveness might be to express bG in the host to catalyze the hydrolysis of SN-38G back to SN-38. In fact, SN-38G excreted in the bile can be converted back to SN-38 by bacterially produced bG in the intestine, which is thought to contribute to the antitumor effect of CPT-11, but also produces intestinal toxicity.…”

PET Imaging of β-Glucuronidase Activity by an Activity-Based 124I-Trapping Probe for the Personalized Glucuronide Prodrug Targeted Therapy

“…Indeed, we also found that Colo205 xenografts exhibited high levels of endogenous bG activity based on the imaging results using TrapG probes. Meanwhile, several studies have found that bG accumulates in the necrotic areas of human cancers (14,18,38,39). In addition, glucuronide conjugates usually exhibit enhanced solubility and decreased cell permeability (3) that greatly increases the utility and specificity of prodrugs or proprobes relying on selective hydrolysis by the bG enzyme.…”