Liposomal, Ring-Opened Camptothecins with Prolonged, Site-Specific Delivery of Active Drug to Solid Tumors

A method for preparing a stable dispersion of a camptothecin, camptothecin prodrug, or analog thereof for administration to a patient in need thereof includes preparing a solution of the camptothecin, wherein the solution has a pH which places substantially an entirety of that camptothecin in a carboxylate form. The camptothecin may be a neutral camptothecin. The solution is next loaded into a liposome including at least one lipid, which may be a phospholipid. An intraliposomal pH is maintained which preserves substantially an entirety of the camptothecin in the carboxylate form. The liposomal dispersion is administered to an individual in need thereof, whereby the liposomes accumulate at and permeate into tumor tissue and an active, lactone form camptothecin is released in situ at the tumor site. Compositions formulated in accordance with the described method for treatment of a cancer in an animal in need thereof are provided also