Amcham defends Pfizer patent

The American Chamber of Commerce (Amcham) in China released a statement saying that its member companies were very concerned with the invalidation of Pfizer's Viagra patent by mainland authorities. China's State Intellectual Property Office revoked the Viagra patent for �insufficient disclosure� on July 5. Amcham said that the patent was revoked in accordance with intellectual property guidelines enacted after the patent was granted. The Amcham statement said "this kind of retroactive rule-making undermines the perceived value of a Chinese patent and creates unpredictability which foreign investors fear most."