Method of making liposomal oligodeoxynucleotide compositions

A method of encapsulating an oligodeoxynucleotide or an analog thereof in liposomes, which comprises:

• a) mixing lipids for constituting said liposomes, and drying said lipids under reduced pressure;
• b) adding to said dried lipids a solution comprising said oligodeoxynucleotide or said analog thereof, wherein said analog is a methylphosphonate, phosphorothioate or phosphoramidate analog, at a ratio of about 1-3 .mu.l of oligonucleotide-containing solution per mg of lipid,
• c) incubating said lipids and said solution for about 4 to 24 hours, and then mixing said lipids and said solution, whereby liposomes are formed;
• and
• d) separating said liposomes from oligodeoxynucleotide or oligodeoxynucleotide analog that is not encapsulated in said liposomes,
• such that said method incorporates at least about 45% of said oligodeoxynucleotide or said analog thereof into said isolated liposomes.