Accumulation of liposomal lipid and encapsulated doxorubicin in murine Lewis lung carcinoma: the lack of beneficial effects by coating liposomes with poly(ethylene glycol). J Pharmacol Exp Ther 280:1319–1327

The efficiency of drug accumulation in tumors was measured after intravenous administration of doxorubicin encapsulated in distearoyl phosphatidylcholine/cholesterol liposomes prepared in the presence or absence of 5 mol % polyethylene glycol-modified phosphatidylethanolamine (PEG-PE). These liposomal formulations of doxorubicin were administered at the maximum tolerated dose in female BDF-1 mice bearing subcutaneously established Lewis Lung carcinoma. The parameters used to determine tumor targeting efficiency (Te) included area under the doxorubicin plasma (AUCP) and tumor (AUCT) concentra-tion-time curves. Extended time-course studies evaluating lipid and drug levels in plasma and tumors during 7 days after administration indicated that the Te (AUCT/AUCP) was greater for liposomes that did not contain PEG-PE. The AUCP afte