Enhanced Antitumor Activity and Reduced Toxicity of 1,3‐Bis(2‐chloroethyl)‐1‐nitrosourea Administered in Lipid Microspheres to Tumor‐bearing Mice

Stable lipid microspheres (LM) and lipid nanospheres (LN) with average diameters of 200 nm and 50 nm, respectively, were used to encapsulate an lipophilic antitumor agent, 1,3‐bis(2‐chloroethyl)‐1‐nitrosourea (BCNU). LM and LN containing BCNU (lipo BCNU and s‐lipo BCNU, respectively) were prepared by homogenizing a soybean oil solution of BCNU with egg yolk lecithin, and their antitumor activity via the intravenous route was tested against L1210 leukemia in mice and compared with that of BCNU dissolved in saline. Both lipo‐BCNU and s‐lipo BCNU showed significantly enhanced antitumor activity with reduced toxicity, when compared with the corresponding doses of BCNU alone. These results suggest that LM and LN may be suitable carriers for lipophilic antitumor agents and may enhance their efficacy.