The America Invents Act (AIA) implemented post-grant proceedings at the Patent Trial and Appeal Board (PTAB) as an alternative to litigation at district courts in the federal circuit. Since its institution, much focus has been placed on the different standards of claim construction used by the PTAB and the district court when construing patents at issue. Whereas the PTAB is to evaluate claims under the broadest reasonable interpretation in light of the specification without any underlying presumption of validity, the district courts are to construe claims in light of the plain and ordinary meaning with the presumption that an asserted claim is valid. Despite this opportunity for diverging claim constructions, a place for resolution of the discrepancies remained at the Federal Circuit, which, until recently, reviewed all claim construction issues de novo. However, on Jan. 20, 2015, the Supreme Court’s holding in Teva Pharm. USA, Inc. v. Sandoz, Inc. added another level of intricacy and increased the level of unpredictability for practitioners seeking to meaningfully construe patent claims.

At issue in Teva is whether the phrase “molecular weight” satisfies the definiteness requirement under 35 U.S.C. § 112, second paragraph. During the prosecution of the patent at issue, Teva overcame a rejection under 35 U.S.C. § 112 alleging the term is indefinite by arguing that the skilled artisan would recognize the term as meaning an average molecular weight (Mw). However, during the prosecution of a different but related patent, Teva argued that the skilled artisan would recognize the term as meaning peak molecular weight (MP). During litigation, Teva provided, inter alia, expert testimony declaring that a skilled artisan, reading the specification of the patent at issue, would recognize that the definition provided during its prosecution was correct, that the definition provided during the prosecution of the related case was incorrect, and therefore an ordinarily skilled artisan would not rely on the latter. Sandoz argued, and provided expert testimony, that the term molecular weight may mean either Mw or Mp, and as such, the skilled artisan would not be able to definitively determine whether subject matter fell within the scope of the claims. Relying on the expert testimony provided by Teva, and presuming the validity of the patent at issue, the district court found the term definite. On appeal, the Federal Circuit construed the term de novo, and overturned the district court’s finding.