Putting its foot down on claim construction, the Federal Circuit looked mainly to a patent’s specification and prosecution history, partially reversing a USPTO Patent Trial and Appeal Board decision. While evidence of common usage went toe-to-toe with the specification’s discussion in the Board’s decision, the Federal Circuit instead prioritized the intrinsic evidence in its decision Friday in Kaken Pharmaceutical v. Iancu.

The patent claimed a topical treatment method for onychomycosis, defined in the specification as “a kind of ... superficial mycosis, ... caused by invading and proliferating in the nail of human or an animal.” It then also defined “superficial mycosis” as occurring “in the skin or visible mucosa,” then broadly defined skin in a way that includes “appendages” such as nails, and further defined a “nail” to include the nail plate, nail bed, and other nearby structures, including parts of the toes (eponychium and hyponychium, shown below) that one might consider as the normally-defined “skin”:

Questions of obviousness hinged on whether the claimed onychomycosis treatment pertained to fungal infections specifically in the nail plate and/or nail bed, or whether it more broadly covered nearby infections of the eponychium and hyponychium. The Board found for the broader construction, noting onychomycosis as a type of superficial mycosis, and therefore including infections of parts of the toe which are conventionally considered to be the “skin.”

Disagreeing, the Federal Circuit particularly looked to intrinsic evidence, including parts of the specification and prosecution history:

• the specification’s background information, characterizing older treatments as insufficiently permeating the think keratin of the nail plate,

• the specification’s mention that its invention provides “good permeability, good retention capacity and conservation of high activity in [the] nail plate,” and

• statements in the prosecution history, distinguishing the claims over topical treatments for other types of mycosis.

Thus, the appellate decision found that the intrinsic evidence demanded a different construction from that received at the Board. In a footnote, the Federal Circuit therefore declined to review the Board’s use of extrinsic evidence, such as expert evidence. The court therefore kicked the decision back to the Board on remand, to consider the issues in light of the properly-construed claims.