U.S. patent office rejects part of Viagra patent Options

[Ren]

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.

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