Increased systemic efficacy of aphidicolin encapsulated in liposomes

Aphidicolin, a tetracyclic diterpene antibiotic produced by Cephalosporium aphidicola, is under investigation as anti-cancer drug. Because of its poor solubility in water, it cannot be administered directly in vivo. Systemic application of aphidicolin glycinate or aphidicolin gamma-cyclodextrin complexes resulted in tumour growth inhibition but not in cures. To improve the pharmacokinetics, a liposomal preparation of aphidicolin was developed and tested in neuroblastoma-bearing (UKF-NB-3) mice. The loading capacity of these liposomes was limited. Therefore, 4.5 mg aphidicolin/kg body weight was the maximum aphidicolin dose that could be applied as liposomal preparation in this approach. Comparison of effects on tumour growth exhibited by aphidicolin liposomes (4.5 mg aphidicolin/kg) given for 15 consecutive days to those of gamma-cyclodextrin inclusion complexes (15 mg aphidicolin/kg) revealed comparable tumour growth inhibition, although aphidicolin concentrations were approximately 3-fold lower. This shows that liposomal encapsulation is a promising strategy for the improvement of systemic anti-cancer activity of aphidicolin.