The U.S Patent and Trademark Office (USPTO) panel has partly ruled against a claim by Viagra manufacturers Pfizer that the Chinese herb yin yang huo, also known as horny goat weed, infringed on their patent rights for the medication.
The judges said that an element of the patent for Viagra was invalid as the medication is not sufficiently different from the traditional Chinese herb.
The ruling is a blow for Pfizer as it will affect an ongoing patent dispute they have with Eli Lilly over the rival company’s Cialis, which has been ongoing since 2002. Pfizer claimed that their method for treating erectile dysfunction was a new invention, but the similarity the blue pill has to horny goat weed means that a precedent has been set that this is not the case.
The USPTO found that both horny goat weed and Viagra act through the same mechanism, the inhibition of the enzyme phosphodieterase-5, or PDE-5. They ruled that ‘the patent claim was the logical step up from using the herb’.
A Pfizer spokesperson has said that the other aspects of the patent remain valid and said that it would not have an impact on Pfizer’s other claims over sildenafil, the active ingredient in Viagra. The firm has not commented on how the decision could impact on the 5-year lawsuit against Eli Lilley.
The company has until the 12th of April to either seek a rehearing from the UPSPTO or appeal the decision through the US Court of Appeals for the Federal Circuit, the body specialising in patent law.