We were made aware recently by our colleagues in Japan of an interesting wrinkle in Japanese patent law that allows pharmaceutical companies to extend the term of Japanese patent protection for their drug compounds, and other important patents, an additional 18 months, when claiming priority to a United States provisional application. The strategy works like this:
- t0 – file a U.S. provisional application
- t12mo – file a PCT application claiming priority to the U.S. provisional application
- t18mo – file a first JP domestic application before the PCT application publishes without claiming priority to the U.S. provisional or PCT application
- t30mo – file a second JP domestic application claiming priority to the first JP domestic application
- t30mo – enter the PCT application into the national stage in Japan
In this scenario, the applicant can receive two patents for substantially the same invention, expiring 18 months apart. Thus, for example, the patent issuing from the PCT application could claim a drug compound, and the patent issuing from the second JP domestic application could claim all pharmaceutical compositions that contain the compound. The patent issuing from the PCT application will expire 20 years from t12mo, while the patent issuing from the second JP domestic application will expire 20 years from t30mo. The strategy works because, under Japanese law, the U.S. provisional application and the first PCT application do not become prior art until they are published, as long as the applications have identical applicants and inventors, and the two applications do not claim the identical invention. The U.S. provisional application and the first PCT application are not prior art to the second JP domestic application because the second JP domestic application enjoys the priority date of the first JP domestic application if filed within one year of the first JP domestic application
Of course, one must be vigilant to prevent public disclosure of the invention before the PCT application publishes, since this public disclosure could qualify as prior art to the first JP domestic application.
This strategy might be a little involved for every patent application filed in Japan, but for patents that are most valuable at the end of their term, such as pharmaceutical compound patents, this is certainly a strategy worth considering. The fact that Japan’s patent term extension laws extend the term of all patents that cover an approved drug product in Japan further validates this strategy and supports its use. If you wish to explore this strategy further, particularly if you do not wish to follow this exact filing sequence, please let us know and we will put you in touch with our Japanese colleagues. Every situation is different and demands the attention of experts in Japanese law at the earliest opportunity.
