Patenting a new second medical indication of a known pharmaceutical compound could help to prolong the lifespan of patents for the pharmaceutical compound. However, because the practice for patenting a second medical indication invention in China is quite different from other jurisdictions such as Europe, the US and Japan, the patent protection of a second medical indication invention in these jurisdictions may not be necessarily available in China.

Moreover, since the current Guidelines for Patent Examination entered into force two years ago, much stricter criteria for novelty and new matter issues make it more and more difficult to get patents for second medical indication inventions in China. It thus may be worthwhile for a patent practitioner to take Chinese patent practice in this field into consideration when drafting the specifications, in view of the importance of getting patent protection for second medical indication invention in China.

Swiss-type claims

Under Article 25 of the Chinese Patent Law, methods for the diagnosis or treatment of diseases are unpatentable subject matters. No patent right will be granted to a claim directed to a second medical indication of a known pharmaceutical compound, if it is presented in the form of a method for the treatment of diseases.

For novelty reasons, a second medical indication of a known pharmaceutical compound cannot be patented either in the form of "compound X for treating disease Y" or in the form of "a pharmaceutical composition comprising a compound X for treating disease Y". The underlying rationale is that the gist for a second medical indication lies in the finding of a new use of a known compound, which cannot render the compound itself novel. It has been a long-established practice in China that a product claim should be defined by the structural features of the product, such as its name, structural formula, and components. It is commonly held that the use feature of a product does not have any definitions on the product per se.

But the current Guidelines do provide some guidance on how to patent a second medical indication of a known pharmaceutical compound in China. According to the current Guidelines, a second medical indication of a known pharmaceutical compound could be patented in the form of Swiss-type use claim, which is presented as "use of compound X in the preparation of a medicament for the treatment of disease Y." The current Guidelines further provide that no patent right shall be granted to the claims directed to the medical use of a pharmaceutical compound if they are presented in such forms as "use of a compound for the treatment of diseases", "use of a compound for the diagnosis of diseases" and "use of a compound as a medicament".

Quite often, a second medical indication invention of a known compound has been initially presented either in the form of a method for the treatment of diseases or in the form of a compound for treating diseases, especially for those applications that have been drafted outside China. An unpatentable subject matter issue or a novelty issue will be raised if a claim is presented in these two forms. It looks like the issues may be easily overcome by simply converting the claim into the Swiss-type use claim. However, due to the amendment, some other issues may arise that will prevent the inventions from being granted if the specifications have not been drafted in line with the Chinese patent practice. Among those issues, novelty issues and new matter issues are the most difficult issues to be dealt with during the prosecution.