A liposome composition comprising a lipophilic prodrug of mitomycin C having an improved pharmacokinetic profile is described. A method for preparing the composition with a solvent system comprised of ethanol and tertiary butanol mixed at an adequate ratio is also described. In an embodiment, the liposome composition is a population of lipid nanoparticles and a pharmaceutically acceptable vehicle, wherein the population of lipid nanoparticles is comprised of a first fraction of spherical liposomes and a second fraction of rod-shaped lipid nanoparticles, where the second fraction is less than about 15% of the population of lipid nanoparticles.