CASRIP Newsletter - Spring/Summer 2006, Volume 13, Issue 2
Invalidation Decision of Viagra Patent revoked in China
By Lizhu Zheng [*]
I. Introduction
On June 2, 2006, the Beijing No. 1 Intermediate People's Court revoked invalidation decision No. 6228, entered by the Patent Reexamination Board ("PRB") of the Chinese Patent Office ("SIPO") and ordered the PRB to enter a new decision for the Viagra patent, CN 94192386.X.
II. Procedural History
The Viagra patent application through the PCT, claimed the priority of British application 9311920.4 and entered China's national phase on December 8, 1995. After three Office Actions and resulting amendments, the Viagra patent, with one single claim, was granted by SIPO on September 19, 2001. Immediately, 13 complaints from one individual and 12 Chinese medicine companies were filed with the PRB challenging the patentability of the Viagra patent.
After an oral hearing on July 5, 2004, the PRB invalidated the Viagra patent for failing to meet the disclosure requirement.[1] It did not decide the other two major causes of action, i.e. claim support from the description,[2] and the nonobvious standard.[3] The patentee Pfizer then brought action against the PRB for the invalidation decision to the Beijing No. 1 Intermediate People's Court, which is the only one trial court to judicially review all administrative decisions of the PRB.
III. Discussion
A. The Viagra Patent in China
The single claim of the Viagra patent is related to the second medical use of Sildenafil in treating erectile dysfunction and reads "the use of 5-[2-ethoxy-5-(4-methyl-1-piperazinylsulphonyl)-phenyl]-1 methyl-3-n-propyl-1, 6-dihydro-7H-pyrazolo[4,3-d]pyrimidin-7-one, or a pharmaceutically acceptable salt thereof, or a pharmaceutical composition containing either entity, for the manufacture of a medicament, for the curative or prophylactic treatment of erectile dysfunction in a male animal, including man."
From the teaching of the description, the well-known compounds for inhibiting cGMP PDEv and inducing penile erection were explained by five classes in a certain order, that is to say, "compounds of general formula (I)" as the first class; "preferred compounds" as the second class for further defining the scope of the first class; "more preferred compounds" as the third class for further defining the scope of the second class; "particularly preferred compounds" as the fourth class for further defining the scope of the third class; and "particularly preferred individual compounds" as the fifth class constituted by nine compounds (Sildenafil is included) selected from the fourth class.
The preferred embodiments cited in the Chinese version of the patent disclosed in vitro test data of "a particularly preferred compound;" however, the counterpart in the original English version was for "an especially preferred compound" with the purpose of showing the compounds of the fifth class. Unfortunately, it is quite hard to distinguish literally whether the test data were relevant to the fourth or the fifth class compounds from the context of the embodiments in the Chinese version of the Viagra patent.
B. Different Interpretations
1. PRB's Arguments
The interested parties have different understandings of the relationship between the test data and the respective class compounds from the embodiments. The PRB thought that the description did not produce a sufficient explanation of the relationship and the third parties on the side of the PRB believed that the test data in the description only applied to compounds of the first and fourth classes from the context of the related embodiments. After reading the description, even after a combination with the prior art, one skilled in the art could not be convinced that the cGMP PDRv inhibitor has such a function for the treatment of male erectile dysfunction ("ED"). In addition, the PRB thought the description had no relation to the further effect of the compounds for treating or taking precaution against male ED, excluding the test data for the fourth class compounds. Furthermore, the PRB believed that the fourth class compounds exceeded 100, so that one skilled in the art could not be certain which compound has the function of treating male ED from the more than 100 compounds, without some inventive labor.
2. Pfizer's Arguments
Plaintiff Pfizer argued that the PRB erred in understanding the facts of the patent, such as whether the patent revealed value IC50 for the compounds of the fourth class. Pfizer pointed out that in the description, the compound showing the pharmacological activity and the test data was an especially preferred compound. The fourth class compounds are a group of compounds defined by the "particularly preferred compounds with formula (I)" and nine specific compounds are listed from the last line on page 5, to the last line of the description on page 6, and named as particularly preferred individual compounds. Therefore, the test data should be applied to the highest fifth class compounds instead of the abstract compounds of the fourth class. Pfizer also argued that the PRB misunderstood the facts because it determined the sufficient disclosure from the view of the public, instead of one skilled in the art as required by Article 26.3 of China's Patent Law.
In addition, Pfizer also argued that the invalidation decision exhibited a higher standard for the Viagra patent than the legal norms of Article 29, section 1 and Article 70, section 2 of TRIPS and Article 26.3 of China's patent law. The accurate understanding of the requirements should be that one skilled in the art, after reading the description, can reproduce the technical solution of the invention, resolve the technical problems and obtain the expected technical effects, without any inventive labor. The PRB misinterpreted the requirements and stated that the second medical use of the invention was not disclosed sufficiently by the description if one skilled in the art had to spend some inventive labor to understand the second medical use of the compound after the teaching of the description and the related prior art.
Pfizer also argued that Mr. Guowen Xu should not be a patent agent for the third parties during the invalidation proceeding before the PRB because he began to represent the third parties shortly after leaving the PRB, where he had worked as a senior reexaminer. This should be forbidden by the relative Chinese laws. The third parties alleged that there was no law concerning professional responsibility preventing a retired person from the PRB from representing clients before the PRB as a patent agent in China.
C. The Court Speaks
The Court interpreted that for the medical inventions, the test data, rather than the single technical solution based on a technical idea, was necessary to prove patentability, and the technical effects should be shown by the test data of the preferred embodiments. As to the second medical use inventions, the test data are required for one skilled in the art to be persuaded that the claimed use will achieve the stated technical objective, otherwise, from the view of realizing the second medical use, the person skilled in the art cannot carry out the claimed invention.
The disputed invention disclosed the compounds from first class to the fifth class in a certain order. The person skilled in the art should have reason to know that the preferred classes have some relationships with the object of the invention. Generally, the test data from some specific compounds disclosed in the preferred embodiments should result from those that can produce the best technical effects for the test. The fifth class compounds are the best preferred embodiment that have analogous structures and, consequently, should have similar pharmacological activities as well. Accordingly, the skilled person in the art should have reasons to know that the claimed compound as one of the nine best preferred compounds has the descriptively therapeutic effect, without spending any inventive labor.
The Court thus held that the invalidation decision No. 6228 was revoked and the PRB was ordered to issue a new decision for the Viagra patent, CN 94192386.X. In addition, the Court held that Mr. Xu, who represented the clients before the PRB, violated no procedural requirement.
IV. Commentary
The Viagra case in China has already received excessive concerns both domestically and overseas. Although China is not a common law country like the United States, the reasoning in the Viagra case by the Beijing No. 1 Intermediate People's Court will be considered by other authorities. Nonetheless, for future efficiency, it would be better to include the reasoning for the preferred embodiments within the relevant provisions or regulations.
