Polymer nanoparticle injection formulation composition containing rapamycin with improved water solubility, preparation method thereof, and anticancer composition for combined use with radiotherapy

A method for treating cancer in a combination therapy with radiation comprising administering to a subject in need thereof a therapeutically effective amount of an injectable composition comprising polymeric nanoparticles containing rapamycin, wherein the composition comprises:

• (i) an A-B type diblock copolymer having a hydrophilic block (A) of methoxy polyethylene glycol and a hydrophobic block (B) of polylactic acid,
• (ii) an alkali metal salt of polylactic acid or its derivative having at least one carboxyl group on its end, and
• (iii) rapamycin as an active ingredient,
• wherein rapamycin is entrapped within the micelle formed from the A-B type diblock copolymer and the alkali metal salt of polylactic acid or its derivative,
• wherein the composition is reconstituted to the rapamycin concentration of 0.1 to 25 mg/ml, and
• wherein the composition is administered at the time of, before or after irradiation to mammalian cancer cell to increase a sensitivity of mammalian cancer cell to radiotherapy.