Federal Circuit Affirms Intrinsic Evidence Trumps Extrinsic Evidence During Claim ConstructionOctober 15, 2020

On October 13, 2020, in Immunex Corp. v. Sanofi-Aventis U.S. LLC, Genzyme Corp., and Regeneron Pharmaceuticals, Inc., the United States Court of Appeals for the Federal Circuit (“Federal Circuit”) affirmed-in-part and dismissed-in-part an appeal from the Patent Trial and Appeal Board (“PTAB”) holding that when it comes to claim construction, intrinsic evidence trumps extrinsic evidence.

The case is a consolidated appeal from two inter partes review (IPR) decisions made by the PTAB. Immunex Corporation (“Immunex”) owns U.S. Patent No. 8,679,487 (“the ‘487 patent”), which covers “isolated human antibodies that bind the human interleukin-4 receptor.” In the first IPR, Sanofi-Aventis, Genzyme Corp., and Regeneron Pharmaceuticals (collectively “Sanofi”) challenged the ‘487 patent, and the PTAB found all of the challenged claims to be invalid. In the second IPR, which involved a subset of the claims at issue in the first IPR, the PTAB decided not to invalidate the patents based on inventorship reasons. The Federal Circuit consolidated the cases on appeal. The Federal Circuit affirmed the PTAB’s decision that the claims were invalid, and, thus, did not reach the question of inventorship.

The claim construction issue in this case is how to interpret the phrase “human antibody” in the claims. “[M]ust a ‘human antibody’ be entirely human? Or may it also be ‘partially human,’ including ‘humanized’?”. Immunex argues that the PTAB erred by construing the term “human antibody” to include not only “fully human” antibodies, but also “partially human” and “humanized” antibodies.

The Federal Circuit concluded that the intrinsic evidence, including the language of the specification and the prosecution history, points to the terms “human antibodies” to include antibodies that are partially human and “humanized”. For example, the Federal Circuit points to the fact that the specification reads, in part “[p]rocedures have been developed for generating human antibodies in non-human animals. The antibodies may be partially human, or preferably completely human.” This passage supports the PTAB’s and Federal Circuit’s construction which provides that the term “human antibodies” includes both partially and fully human antibodies. Immunex disagreed with the Federal Circuit’s reading of this passage, but the Federal Circuit found the argument unpersuasive. Further, the Federal Circuit recognizes that the specification states that some human antibodies are fully human, implying that some may only be partially human. The Federal Circuit also examined the prosecution history and found it to support the court’s claim construction. For example, the Federal Circuit acknowledges that in another patent application in the same family as the patent at issue, Immunex used both “fully human” and “human”, indicating that the two terms are not synonymous.

The Federal Circuit also considered extrinsic evidence including expert testimony, journal articles, catalogs, and other documents. The Federal Circuit held that a court may look to extrinsic evidence only when it does not conflict with the apparent meaning discerned from the intrinsic evidence. The intrinsic evidence has priority over extrinsic evidence. The Federal Circuit also noted that “[w]hile extrinsic evidence may sometimes illuminate a well-understood technical meaning, … that does not mean that litigants can introduce ambiguity in a way that disregards language usage in the patent itself.”

Accordingly, the Federal Circuit agreed with the PTAB’s claim construction and affirmed its decision to invalidate the claims at issue. Here, the Federal Circuit reiterated the principle that intrinsic evidence trumps extrinsic evidence during claim construction.

Joseph M. Hallman is a Patent Attorney in the Mechanical and Electrical Patent Practice Groups at McKee, Voorhees & Sease, PLC. For additional information please visit www.ipmvs.com or contact Joseph directly via email at joseph.hallman@ipmvs.com 

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