In the context of Immunex’s patent on IL-4 antibodies, the Federal Circuit says yes.

On October 13, 2020, the Federal Circuit affirmed the Patent Trial and Appeal Board’s (the “Board”) final written decision in IPR2017-01884, holding invalid all claims of U.S. Patent No. 8,679,487 (“the ’487 patent”) assigned to Immunex. The ‘487 patent is drawn to an isolated “human antibody” that binds to the human interleukin-4 (IL-4) receptor in competition with a reference antibody defined by specific heavy- and light- chain variable regions.

The Board found the claims invalid as obvious in view of a reference (Hart) that disclosed a murine antibody that binds IL-4 as required by claim 1, and a reference (Schering-Plough) that teaches humanizing of such murine antibodies by grafting CDRs onto an otherwise fully human antibody. The Board determined that a “humanized” antibody met its construction of “human” antibody, and therefore determined that claims 1-17 of the ‘487 patent were unpatentable as obvious over the cited references.

The issue before the Federal Circuit was whether an isolated “human” antibody is limited to a fully human antibody or further encompass a partially human antibody, including a “humanized” antibody as construed by the Board.

The Federal Circuit first determined that the broadest reasonable interpretation (“BRI”) standard applied, despite the ’487 patent having expired on May 26, 2020, two months prior to the oral argument on appeal. The patent expired early because Immunex filed a terminal disclaimer while the case was on appeal. The court recognized that the Phillips standard has been applied in IPRs where a patent expired on an appeal (citing Apple Inc. v. Andrea Elecs. Corp., 949 F.3d 697, 707 (Fed Cir. 2020)); however, the court distinguished Andrea Electronics, because in that case the patent term expired in its natural course, whereas Immunex’s action abruptly cut short the patent’s term after the parties had fully briefed claim construction under the BRI standard. Therefore, the court found it appropriate to “review the decision from which an appeal is taken on the record before the Patent and Trademark Office.” 35 U.S.C. § 144.

Next, the court determined that the Board did not err in construing the term “human” antibody to encompass not only fully human but also partially human antibodies, based on the intrinsic record. The specification and prosecution history supported the notion that the “human” antibody as claimed encompassed both fully “human” antibody and a partially human antibody. The specification did not include an express definition of “human antibody.” In several instances, however, the specification refers to some “human” antibodies as “fully human” but includes other antibodies in the “human” category. For example, the specification states: “[p]rocedures have been developed for generating human antibodies in non-human animals. The antibodies may be partially human, or preferably completely human.” ‘487 patent at col. 19 ll. 41-44. The court found no “clear and unmistakable” disavowal of partially human embodiments during prosecution. Additionally, the Examiner expressly wrote that the amended “human” antibodies encompassed “humanized” antibodies, yet Immunex made no effort to correct the examiner of this understanding. Accordingly, the court determined that the language of the specification confirms the broadest reasonable interpretation of “human antibodies” as including partially human, “humanized” antibodies, and the prosecution history also supports the Board’s construction. The court gave little weight to the extrinsic evidence because it found the intrinsic record unequivocal.

Lastly, the court addressed the Board’s departure from an earlier district court’s claim construction. Two months prior to oral hearing in the IPR, a district court construed “human” in the context of the ’487 patent to mean “fully human” only. See Immunex Corp. v. Sanofi, No. CV 17-02613 SJO, 2018 WL 6252460, at *12-14 (C.D. Cal. Aug. 24, 2018). Immunex argued that under Power Integration, Inc v. Lee, 797 F.3d 1318, 1326 (Fed. Cir. 2015), the Board had not sufficiently explained why under the BRI standard, it reached a broader construction than that of the district court. However, the Court determined that the “Board’s opinion was sufficiently detailed to permit meaningful appellate review”, under Power Integrations, and concluded that the Board’s construction of the “human” antibody was correct.

There are a number of takeaways from this case. First, a party cannot alter the claim construction standard in an IPR by filing a terminal disclaimer to abruptly shorten the patent term. Second, Power Integrations sets a relatively low bar for the Board to explain why its claim construction under the BRI differs from a district court’s construction. Lastly, it is worthwhile to expressly specify the type of antibody intended in the claims. Further, it is recommended that the specification specifically define terms like “antibody” and “human antibody,” as the court will favor intrinsic evidence over extrinsic evidence of the meaning such terms may have to a person of skill in the art.