Daunoxome® Treatment of Solid Tumors: Preclinical and Clinical Investigations

Abstract

Daunorubicin has been entrapped into small unilamellar vesicles (50-80 nm dia) composed of a 2:1 mole ratio of highly purified DSPC:cholesterol. In earlier studies, liposomes of this size and composition had been demonstrated to deliver their entrapped contents selectively to a wide range of solid tumors in vivo. Preclinical and initial clinical investigations of these daunorubicin liposomes (DaunoXome) are discussed. In one murine solid tumor model (P1798 lymphosarcoma), a ten-fold increased delivery of entrapped daunorubicin to tumor tissue was observed. Efficacy studies in the same model indicated improved tumor regression and extended life spans that correlated with the observed degree of enhanced tumor drug delivery. In a second tumor model (MA16C mammary adenocarcinoma), a ten-fold enhancement in efficacy again was demonstrated. In terms of median survival times and long term survival rate, DaunoXome dosed at 2 mg/kg (daunorubicin) demonstrated an efficacy comparable to free drug at 20 mg/kg. Clinical pharmacokinetics paralleled findings from animal studies. In humans, DaunoXome produced daunorubicin plasma AUC levels that were more than 35-fold greater than those reported for comparable doses of free drug at 80 mg/m². Response rates above 50% have been shown for treatment of Kaposi's sarcoma. A low incidence of side effects has been observed and HIV positive patients have been able to continue antiviral therapy during DaunoXome treatments. Cardiotoxicity has not manifested clinically even for patients receiving in excess of 1 gram/m² cumulative daunorubicin.