Center for Advanced Study & Research on Innovation Policy


CASRIP Newsletter - Spring/Summer 2006, Volume 13, Issue 2

Invalidation Decisionof Viagra Patent revoked in China

By Lizhu Zheng [*]

I.          Introduction

On June 2, 2006, the BeijingNo. 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, CN94192386.X.

II.        Procedural History

The Viagra patent applicationthrough the PCT, claimed the priority of British application 9311920.4 and entered China's national phase on December 8, 1995.  After three Office Actions andresulting amendments, the Viagra patent, with one single claim, was granted by SIPOon September 19, 2001.  Immediately, 13 complaints from one individual and 12Chinese medicine companies were filed with the PRB challenging thepatentability 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 invalidationdecision to the Beijing No. 1 Intermediate People's Court, which is the onlyone trial court to judicially review all administrative decisions of the PRB.

III.       Discussion

A.        The Viagra Patent in China

The single claim of the Viagrapatent is related to the second medical use of Sildenafil in treating erectiledysfunction and reads "the use of5-[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 compositioncontaining either entity, for the manufacture of a medicament, for the curativeor prophylactic treatment of erectile dysfunction in a male animal, includingman."

From the teaching of thedescription, the well-known compounds for inhibiting cGMP PDEv and inducingpenile erection were explained by five classes in a certain order, that is tosay, "compounds of general formula (I)" as the first class; "preferredcompounds" 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 ofthe second class; "particularly preferred compounds" as the fourth class forfurther defining the scope of the third class; and "particularly preferredindividual compounds" as the fifth class constituted by nine compounds (Sildenafilis included) selected from the fourth class.

The preferred embodimentscited in the Chinese version of the patent disclosed in vitro test data of "aparticularly preferred compound;" however, the counterpart in the originalEnglish version was for "an especially preferred compound" with the purpose ofshowing the compounds of the fifth class.  Unfortunately, it is quite hard todistinguish literally whether the test data were relevant to the fourth or thefifth class compounds from the context of the embodiments in the Chineseversion of the Viagra patent.

B.        Different Interpretations
1.         PRB's Arguments

The interested parties havedifferent understandings of the relationship between the test data and therespective class compounds from the embodiments.  The PRB thought that thedescription did not produce a sufficient explanation of the relationship andthe third parties on the side of the PRB believed that the test data in thedescription only applied to compounds of the first and fourth classes from thecontext of the related embodiments.  After reading the description, even after acombination with the prior art, one skilled in the art could not be convincedthat the cGMP PDRv inhibitor has such a function for the treatment of male erectiledysfunction ("ED").  In addition, the PRB thought the description had no relationto the further effect of the compounds for treating or taking precautionagainst male ED, excluding the test data for the fourth class compounds.  Furthermore,the PRB believed that the fourth class compounds exceeded 100, so that oneskilled in the art could not be certain which compound has the function oftreating male ED from the more than 100 compounds, without some inventivelabor.

2.         Pfizer's Arguments

Plaintiff Pfizer argued that thePRB erred in understanding the facts of the patent, such as whether the patent revealedvalue IC50 for the compounds of the fourth class. Pfizer pointed outthat in the description, the compound showing the pharmacological activity and the test data was an especially preferredcompound. The fourth class compounds are a group of compounds defined by the "particularlypreferred compounds with formula (I)" and nine specific compounds are listed fromthe last line on page 5, to the last line of the description on page 6, andnamed as particularly preferredindividual compounds.  Therefore, the test data should be applied to thehighest fifth class compounds instead of the abstract compounds of the fourthclass.  Pfizer also argued that the PRB misunderstood the facts because itdetermined the sufficient disclosure from the view of the public, instead of oneskilled in the art as required by Article 26.3 of China's Patent Law.

In addition, Pfizer alsoargued that the invalidation decision exhibited a higher standard for the Viagrapatent than the legal norms of Article 29, section 1 and Article 70, section 2 ofTRIPS and Article 26.3 of China's patent law.  The accurate understanding ofthe requirements should be that one skilled in the art, after reading thedescription, can reproduce the technical solution of the invention, resolve thetechnical problems and obtain the expected technical effects, without anyinventive labor.  The PRB misinterpreted the requirements and stated that the secondmedical use of the invention was not disclosed sufficiently by the descriptionif one skilled in the art had to spend some inventive labor to understand thesecond medical use of the compound after the teaching of the description andthe related prior art.

Pfizer also argued that Mr.Guowen Xu should not be a patent agent for the third parties during theinvalidation proceeding before the PRB because he began to represent the thirdparties shortly after leaving the PRB, where he had worked as a senior reexaminer. This should be forbidden by the relative Chinese laws.  The third partiesalleged that there was no law concerning professional responsibility preventinga retired person from the PRB from representing clients before the PRB as apatent agent in China.

C.        The Court Speaks

The Court interpreted thatfor the medical inventions, the test data, rather than the single technicalsolution based on a technical idea, was necessary to prove patentability, andthe technical effects should be shown by the test data of the preferredembodiments.  As to the second medical use inventions, the test data are requiredfor one skilled in the art to be persuaded that the claimed use will achievethe stated technical objective, otherwise, from the view of realizing thesecond medical use, the person skilled in the art cannot carry out the claimedinvention.

The disputed inventiondisclosed 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 preferredclasses have some relationships with the object of the invention. Generally,the test data from some specific compounds disclosed in the preferredembodiments should result from those that can produce the best technical effectsfor the test.  The fifth class compounds are the best preferred embodiment thathave analogous structures and, consequently, should have similarpharmacological activities as well. Accordingly, the skilled person in the art shouldhave reasons to know that the claimed compound as one of the nine bestpreferred compounds has the descriptively therapeutic effect, without spending anyinventive labor.

The Court thus held that theinvalidation decision No. 6228 was revoked and the PRB was ordered to issue anew decision for the Viagra patent, CN 94192386.X.  In addition, the Court heldthat Mr. Xu, who represented the clients before the PRB, violated no proceduralrequirement.

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 BeijingNo. 1 Intermediate People's Court will be considered by other authorities.  Nonetheless,for future efficiency, it would be better to include the reasoning for thepreferred embodiments within the relevant provisions or regulations.

[*] Lizhu Zheng is a patent attorney from China and a student in the IP LL.M. program at the University of Washington School of Law.

[1] China's Patent Law, Article 26, para. 3.

[2] Id.

[3] China's Patent Law, Article 22, Para.3

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