Method of preparing (+)-1,4-dihydro-7-[(3S,4S)-3-methoxy-4-(methylamino)-1-pyrrolidinyl]-4-oxo-1-(2-thiazolyl)-1,8-naphthyridine-3-carboxylic acid

1. A method for treating rhabdomyosarcoma comprising administering a composition, wherein the composition comprises at least 99.95% (+)-1,4-dihydro-7-[(3S,4S)-3-methoxy-4-(methylamino)-1-pyrrolidinyl]-4-oxo-1-(2-thiazolyl)-1,8-naphthyridine-3-carboxylic acid and less than 0.05% (+)-1,4-dihydro-7-[(3S,4S)-3-methoxy-4-amino-1-pyrrolidinyl]-4-oxo-1-(2-thiazolyl)-1,8-naphthyridine-3-carboxylic acid based on total weight of the composition to a subject in need of thereof.

2. The method of claim 1 further comprising administering a therapeutically effective dose of an anti-cancer agent selected from an alkylating agent, antimetabolite, an aurora kinase inhibitor, a purine antagonist, a pyrimidine antagonist, a spindle poison, a podophyllotoxin, an antibiotic, a nitrosourea, an inorganic ion, an enzyme, a hormone, a topoisomerase II inhibitors or poison, an EGFR inhibitor, an antibody, an IMID, a Bcl-2 inhibitor, a VEGF inhibitor, a proteasome inhibitor, a cyclin-dependent kinase inhibitor, and dexamethasone.

3. The method of claim 2 , wherein the second agent is selected from cytarabine, carboplatin, cisplatin, gemcitabine, anti-emetic agent and a combination thereof.

4. The method of claim 1 , wherein the composition is a lyophilized powder.

5. The method of claim 1 , wherein the composition is for intravenous administration.

6. The method of claim 4 suitable for reconstitution with water to provide a liquid dosage form for intravenous administration.

7. The method of claim 1 comprising administering about 10-100 mg of the composition.