Pfizer’s patent US No. 6,469,012 relates to its best selling drug “Viagra”. Following patent infringement claims by Pfizer against Eli Lilly, Lilly ICOS (makers of “Cialis”) and Bayer (maker of “Levitra”) had sought for re-examination of Pfizer’s ‘012 Patent.
The claim that is said to cover both “Levitra” and “Cialis” is claim 24.
24. A method of treating erectile dysfunction in a male human, comprising orally administering to a male human in need of such treatment an effective amount of a selective CGMP PDE sub-v inhibitor, or a pharmaceutically acceptable salt thereof, of a pharmaceutical composition containing either entity.
During the re-examination, the examiner rejected claim 24 as anticipated by each of five references and also issued an obviousness-type double patenting rejection based on 3 other Pfizer patents. The Board affirmed the decision in February 2010.
In particular, the Board agreed that prior art descriptions of oral administration of the herbYin Yang Huo (aka Horny Goat Weed) serve as anticipatory prior art.
Pfizer has the opportunity to request for a re-hearing and may also appeal the Board’s decision.
It is to be noted that not all claims in the ‘012 Patent were invalidated. It is the broad claim on the use of an entire class of molecules, defined functionally, not structurally, that was declared invalid. The narrower claims that cover the use of sildenafil, Pfizer’s actual product, and similar compounds, defined in structural terms, were upheld. Small consolation for Pfizer, since these claims are not infringed by vardenafil (Levitra) or tadalafil (Cialis).
Patent claims have to drafted carefully so as not to be too broad (likely to include prior art / knowledge) or too narrow (likely to benefit competitors who can easily circumvent the patent claim). Determining the scope of patent claims is often a balancing exercise.
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