Formulations of antisense oligonucleotides (asODNs) against c-myb or c-myc protooncogenes have been prepared by a new technique that sequesters cationic lipid in the interior of a lipid particle. This technique results in high loading efficiency for the asODNs, small particle size and good stability. When targeted against melanoma cells or neuroblastoma cells via anti-GD(2) coupled at the particle surface, increased cell binding to the cells could be demonstrated. Targeted formulations showed greater inhibition of cell proliferation compared to non-targeted formulations or free drug. Inhibition of cell proliferation was demonstrated to be due to down-regulation of c-myb or c-myc protein expression. The formulations have long-circulation times in vivo, and evaluation for in vivo antitumor activity is currently underway.