Hydrophobic cis-platinum complexes efficiently incorporated into liposomes

A method of treating an animal afflicted with tumor cells sensitive to a platinum (II) four-coordinate complex, comprising administering to the animal a pharmaceutically effective amount of a liposome which comprises a phospholipid and a platinum (II) four-coordinate complex having the formula:

• ##STR15## where R.sub.1 and R.sub.2 are neo-decanoato of the formula ##STR16## where two of R, R', and R" are methyl, ethyl, or propyl;
• and wherein R.sub.3 and R.sub.4 are each amines of the formula:
• ##STR17## wherein R.sub.5 is selected from the group consisting of hydrogen, alkyl, aryl, aralkyl, alkenyl, cycloalkyl, or cycloalkenyl having between 1 and 20 carbon atoms;
• or
• wherein R.sub.3 and R.sub.4, when linked together, are selected from the group consisting of cycloalkyl-1,2-diamino having between about 3 and 7 carbon atoms, and alkyl-vicinal-diamino having between about 2 and 12 carbon atoms;
• and
• said complex is defined further as being substantially soluble in methanol or chloroform and substantially insoluble in water.