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

1. 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.

2. The method according to claim 1 , wherein the number average molecular weight of the hydrophilic block (A) of the diblock copolymer is 500 to 20,000 daltons, the number average molecular weight of the hydrophobic block (B) of the diblock copolymer is 500 to 10,000 daltons, and the content of the hydrophilic block (A) in the diblock copolymer is 40 to 70 wt % on the basis of total 100 wt % of the diblock copolymer.

3. The method according to claim 1 , wherein the polylactic acid or its derivative having at least one carboxyl group on its end is one or more selected from the group consisting of polylactic acid, polylactide, polyglycolide, polymandelic acid, polycaprolactone, polyanhydride and copolymers thereof, and its number average molecular weight is 500 to 2,500 daltons.

4. The method according to claim 1 , wherein the alkali metal is one or more monovalent metals selected from the group consisting of sodium, potassium and lithium.

5. The method according to claim 1 , wherein the composition further comprises divalent or trivalent metal ion.

6. The method according to claim 5 , wherein the divalent or trivalent metal ion is divalent or trivalent cation of the metal selected from the group consisting of calcium, magnesium, barium, chrome, iron, manganese, nickel, copper, zinc and aluminum.

7. The method according to claim 1 , wherein the weight ratio of the A-B type diblock copolymer and the alkali metal salt of polylactic acid or its derivative having at least one carboxyl group on its end is 9:1 to 3:7.

8. The method according to claim 1 , wherein the composition is administered at a timing of 1 minute to 7 days before irradiation.

9. The method according to claim 1 , wherein chemotherapy in combination with radiotherapy is practiced 1 to 5 times per week over a period of 4 to 12 weeks.