In May 1994, Pfizer(www.pfizer.com) filed a patent cooperation treaty (PCT) application on pyrazolopyrimidinones for the treatment of impotence. On September 19, 2001, a Chinese patent, CN 1124926, was issued with a single claim; i.e., “use of a pharmaceutical composition containing sildenafil for preparing a medicine for treating erectile dysfunction.” On October 10, 2001, an invalidation request was filed by a coalition of 12 Chinese companies. This request was filed with the Patent Reexamination Board (PRB).
In July of 2004, the PRB invalidated CN 1124926 for lack of support in the specification. A full written decision was not released at that time. However the language released by the PRB at the time the Pfizer decision was announced stated that with the technical descriptions in the specifications of the patent and available technologies in the field, the compound cannot be proven to cure or prevent impotence without the creative labor of technical personnel.
The type of patent in the Viagra case is a “second medical use claim.” In these types of cases, the law requires that the specification disclose 1) the claimed compound and 2) that the use of the compound has specific therapeutic effect. A review of CN 1124926 shows that the formula disclosed in the application covers over 1,000 compounds. Nine compounds are specifically listed, including sildenafil. A limited amount of data is presented in the specification; however, it is not disclosed which of the preferred compounds was used to generate the data. Data to support sildenafil was submitted during the reexamination proceeding.
The case was appealed to Beijing Intermediate People’s Court. On June 2, 2006, it overturned the PRB ruling of patent invalidity in the Viagra case. The ruling was heralded as groundbreaking for giving improved support of IP rights protection for foreign companies. After the judgment of the Intermediate Court, the case was remanded back to the PRB to determine whether the remaining grounds that were raised by the local pharmaceutical companies would invalidate the patent. Judgment is pending. Pfizer is currently pursuing the same Chinese company in an infringement action.
The western press was critical of the PRB’s decision. This criticism of the PRB decision, however, may not be fair in view of the specific requirement of Chinese patent law and the deficiencies of the Pfizer patent. Indeed, there was so much negative press that many companies have been unduly prejudiced against filing for pharmaceutical patent protection in China. The failure to file and the subsequent loss of rights is more detrimental than any potential loss of rights that could occur before the PRB.
Foreign filing is not an afterthought. Care must be taken from the beginning to provide an application that will be successful. Consult with an attorney knowledgeable about patent law in China before a priority document is prepared to understand the general requirements for filing in China. It is important to file a PCT application in the form to be prosecuted in China. Additionally, the sufficiency of data and publication dates must be monitored to maximize the likelihood that claims will issue.
From the Viagra patent controversy, the following strategy might be adopted: Considering the high requirement for data support of each species, it may in fact be strategically more useful to just describe and claim the species that have data support and file additional applications on the other species if and when they become available, especially if it is likely that some nominal data could be obtained before the publication of the priority application destroys the inventiveness of the subsequently claimed species.