U.S. Patent and Trademark Office Rejects Part of Viagra Patent
February 17, 2010

The U.S. Patent and Trademark Office has partially rejected a patent on Pfizer Inc's impotence drug Viagra because it works in a way similar to the Chinese herb Yin Yang Huo, which is sold on websites under the colorful name Horny Goat Weed. An appeals board of the patent agency, in a February 12 decision, upheld an earlier finding that an element of the Viagra patent did not represent a new invention.

The claims came under contention as part of a patent infringement lawsuit Pfizer filed against Eli Lilly and Co, which makes the rival drug Cialis. The board of patent appeals said in a ruling posted on its website on Tuesday that a chemical ingredient of Yin Yang Huo, which is used to treat impotence and sometimes sold as an alleged aphrodisiac, is similar to the enzyme inhibitor found in Viagra.

"The decision has no effect on Pfizer's patent claims relating to Viagra," Pfizer spokesman Chris Loder said. Pfizer has the right to seek a rehearing or appeal the decision," Loder said, declining to provide a time frame under which an appeal might be filed. The patent in question, which Pfizer contends does not expire until 2019, "contains many other claims directed solely to the use of sildenafil to treat erectile dysfunction and these remain in effect," Loder said, using the chemical name for Viagra. Viagra had sales of nearly $2 billion in 2009.