You can apply for a patent.
Article 25 of the Patent Law:
Article 25 does not grant patent rights for the following items:
(1) Scientific discoveries;
p>(2) Rules and methods of intellectual activities;
(3) Diagnosis and treatment methods of diseases;
(4) Animal and plant varieties;
(5) Substances obtained by atomic nucleus transformation;
(6) Designs made on the patterns, colors, or a combination of the two of flat printed materials that mainly serve as a mark.
Patent rights may be granted in accordance with the provisions of this Law for the production methods of the products listed in item (4) of the preceding paragraph.
If the medicinal use of a substance is applied for a patent with claims such as "used to treat diseases", "used to diagnose diseases", "used
as a medicine", etc., It falls under Article 25, Paragraph 1, Item (3) of the Patent Law, "Methods for diagnosis and treatment of diseases", and therefore cannot be granted a patent; however, because Drugs and their preparation methods can be granted patent rights in accordance with the law. Therefore, the invention of the medical use of a substance can be claimed as a drug or, for example,
"application in pharmaceuticals", "in preparation" "Application in medicines to treat a certain disease" etc.
Applying for a patent for use claims belonging to the pharmaceutical method type does not fall under the Patent Law
Article 25, Paragraph 1 (3) The circumstances specified in paragraph (3).
Examination Guidelines Page 126: Although the method of using drugs to treat diseases cannot be patented, the drug itself can be patented.