Antitumor activity and pharmacokinetics of liposomes containing lipophilic gemcitabine prodrugs

Background: Gemcitabine is a deoxycytidine analogue that exhibits antitumoral activity against adenocarcinomas of the colon, lung and pancreas. After intravenous injection, gemcitabine is rapidly converted to the inactive metabolite 2'-deoxy-2,2'-difluorouridine by cytidine deaminase. Materials and Methods: To improve the pharmacokinetic behavior and the antitumor activity of the drug, the gemcitabine prodrug, 4-(N)-stearoylgemcitabine (C18gem) was incorporated in liposomes and both the pharmacokinetic and the in vivo activity of this formulation intravenously or peritumorally administered in nude female CR1:Nu/Nu(CD-1)BR mice grafted with HT-29 and KB 396p cells were studied. Results: The C18gem-liposomes showed both higher plasma half life and tumor regression than control and gemcitabine. Conclusion: The incorporation of C18gem-prodrug in liposomes increased the plasma half life of the drug resulting in increased accumulation in the tumor cells and a higher level of antitumoral efficacy. The results obtained with different tumors sensitive to gemcitabine support the efficacy of this proposed drug delivery system.