UMass obtained patents for a skin care lotion and sued L’Oreal for patent infringement in district court. The claims of the patents recited “topically applying to the skin a composition comprising a concentration of adenosine” and further recited “wherein the adenosine concentration applied to the dermal cells is [10^-3 or 10^-4] M to 10^-7 M.” L’Oreal responded with an inter partes review (IPR) challenges at the Patent Trial and Appeal Board (PTAB) of the United States Patent and Trademark Office (USPTO). L’Oreal’s prior art references were directed to showing a topical solution having the claimed concentration being applied to the epidermis of the skin. UMass argued that the claimed concentration must be present underneath the epidermis at the dermal cells, and because L’Oreal did not establish the concentration at the dermis, it could not prevail. The PTAB agreed, denying institution of L’Oreal’s IPR challenges. L’Oreal could not appeal the denial of institution because the IPR statute precludes it. 

Now back before the district court, UMass urged adoption of the same claim construction, and L’Oreal again urged that the concentration should be construed to be that of the lotion applied to the epidermis. The district court, following the lead of the PTAB, agreed with UMass. L’Oreal then pointed out that such a construction would render the claims indefinite, and the district court agreed and invalidated the claims.

On appeal, the Federal Circuit reversed. It held L’Oreal was right all along--the claim should be interpreted as referring to the concentration of the lotion applied to the skin, that is the epidermis, based on the specification of the patents and an explanation in the prosecution history when the concentration limitation was added. This meant the indefiniteness ruling was incorrect because it was based on an incorrect claim construction. But reversal of the indefiniteness ruling on that basis might have given UMass a Pyrrhic victory. By adopting L’Oreal’s construction, L’Oreal is now able to rely on the prior art references used in the failed IPRs to invalidate the claims.