Fed Circuit affirms cancellation of Anacor antifungal patents
Anacor Pharmaceuticals has unsuccessfully challenged the invalidation of four patents covering Kerydin (tavaborole), an antifungal treatment for nails.
The US Patent Trial and Appeal Board invalidated the patents through inter partes review, following a petition from FlatWing Pharmaceuticals.
In its decision, the PTAB concluded that the patents were invalid as obvious, due to a combination of prior art which disclosed the use of certain antifungal treatments at specific concentrations.
Anacor appealed to the US Court of Appeals for the Federal Circuit, arguing that the prior art does not disclose the use of tavaborole at a 5% concentration to treat fungal nail infections.
On appeal, Anacor challenged the PTAB’s position that the claimed 5% composition of tavaborole would have been obvious as a “product of routine optimisation” to a person of ordinary skill in the art.
Flatwing replied that the PTAB was correct to find that the prior art taught the effective use of another antifungal econazole with a 5% concentration, “and since tavaborole is a smaller
molecule than econazole, a skilled artisan would have expected that a similar tavaborole composition would perform as well or better”.
“Flatwing adds that there is a clear relationship between antifungal concentration and nail penetration, making tavaborole concentration a result-effective variable, and merely selecting a concentration from a known range is obvious,” court documents stated.
The Federal Circuit sided with Flatwing, finding that a person of ordinary skill in the art would have known to use the 5% concentration for successful penetration of the nail.
The court said Anacor’s argument that tavaborole, an organoboron compound, would have presented “special challenges” was “unpersuasive”.
Organoboron compounds are chemical compounds of boron and carbon. Anacor claimed the reactivity of organoboron compounds meant it would not have been obvious to formulate tavaborole for the claimed purpose.
“The Board reasonably credited testimony from Flatwing’s expert that the claimed composition could have been made according to well-known formulation techniques, and tavaborole’s potential reactivity as an organoboron compound would not have been an important consideration,” the Federal Circuit decision said.
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