CPX-1 Liposome Injection is a liposomal formulation of a fixed combination of the antineoplastic drugs irinotecan HCl and floxuridine. The two drugs are present inside the liposome in a fixed 1:1 molar ratio. CPX-1 was developed as a means of delivering and preserving a fixed 1:1 molar ratio of the two drugs. This ratio was found in vitro and in vivo models of cancer to have synergistic anti-cancer activity and preservation and delivery of this ratio is important because other ratios of these two drugs have been found to be antagonistic or only additive. Both floxuridine and irinotecan HCl are active chemotherapeutic agents, each approved for clinical use in the United States and Canada for colorectal cancer. Current practice routinely administers 5- fluorouracil with irinotecan in combination regimens in first or second line treatment without the means of preserving the synergistic ratio.