Enhancement of chemotherapeutic effect by entrapping 1-beta-D-arabinofuranosylcytosine in lipid vesicles and its mode of action.

a-beta-D-arabinofuranosylcytosine (ara-C) trapped in multilamellar liposomes exerted enhanced chemotherapeutic effect against L1210 murine leukemia. Among four types of liposomes, the one composed of sphingomyelin, stearylamine and cholesterol was most potent in enhancing chemotherapeutic effect of ara-C. And the findings that ara-C was released gradually from liposome in vitro and that ara-C in liposome was chemotherapeutically effective against subsequently inoculated L1210 cells suggested that slow but long-lasting release of ara-C from liposome was partially responsible for enhanced chemotherapeutic effect.