The latest legal battle over patent rights in China for the impotency drug Viagra began in a Beijing court Wednesday.

Drug maker Pfizer is suing the Patent Reexamination Board (PRB) of the State Intellectual Property Office for wrongfully invalidating its China patent for the use of sildenafil, the active ingredient in Viagra, a drug taken for male erectile dysfunction.

During the case's first hearing at Beijing No.1 Intermediate People's Court, Pfizer called for the withdrawal of the PRB's decision, which was passed in July 2004.

The defendant insisted its conclusion had been "right and legal with correct application of laws and regulations."

In the meantime, Pfizer's patent on Viagra remains valid and enforceable in China, pending a final court decision, whether from the current hearings or, if either side contests the intermediate court's verdict, from the Beijing Higher People's Court.

Pfizer filed a patent application in May 1994 for the use of sildenafil citrate in its products in China, which the State Intellectual Property Office granted after seven years of examination.

However, one individual whose identity was not reported and 12 domestic companies challenged the validity of the decision, and the PRB invalidated the patent on the grounds of insufficient disclosure of the claimed invention.

The board claimed the patent manual failed to provide convincing technical content, but Tai Hong, Pfizer's attorney, argued the patent directions were sufficient.

"The decision made by the PRB had errors in facts and (was an) erroneous application of the law," she said.

Tai said the decision by the PRB violated the Trade-Related Aspects of Intellectual Property Rights (TRIPS) agreements.

She also stated that since the attorney involved in the application for invalidity of the patent, Xu Guowen, was a retired official with the PRB, the decision procedure was inappropriate.

Jin Zejian, for the defendant, told the court the 2004 decision was a correct interpretation of Patent Law and relevant examination guidance.

"To invalidate a patent that does not accord with the Patent Law was also to execute the TRIPS agreement," he said.

As for Xu's qualifications, the defendant argued that there was no law or regulation prohibiting retired PRB staff from acting as patent attorneys.

The case has caused widespread concern over intellectual property rights (IPR) protection for overseas enterprises in China.

The American Chamber of Commerce-China said last July that the PRB's decision was a step backward for IPR protection.

However, Li Shunde, an IPR scholar from the Chinese Academy of Social Sciences was quoted by China Economic Times as saying that it was "legal."

(China Daily March 31, 2005)