In Immunex Corp. v. Sanofi-Aventis U.S. LLC, the Federal Circuit held that a patentee cannot avoid the broadest reasonable interpretation (“BRI”) claim construction standard where the patent is prematurely terminated via terminal disclaimer, after completion of appellate briefing.

This case was a consolidated appeal from two IPRs decided using the BRI standard. This standard, which the USPTO uses for examination, is often considered to give broader claim scope than the Phillips standard, which courts use in infringement litigation. Notably, in 2018, after these IPRs were instituted, a change in USPTO rules established the Phillips standard for use in all IPRs.

After appellate briefing, the patentee accelerated expiration by terminally disclaiming its patent, requesting appellate review of the Board’s claim construction under the Phillips standard, the standard used for expired patents, instead of the BRI standard.  The Federal Circuit found this procedurally accelerated expiration, at this stage of the proceeding, insufficient to invoke the Phillips standard.

The Federal Circuit reviewed claim construction of the term “human antibodies” as covering both fully human antibodies and “humanized” antibodies, noting the Board’s conclusion that “humanized” antibodies were obvious over prior art. The Court noted that “humanized” antibodies were usually defined as antibodies that are almost entirely human in origin, with the only exception at the complementarity-determining regions (“CDRs”) of the antibody where non-human sequences may exist. In contrast, fully human antibodies are antibodies that are completely human in origin, including at the CDRs.

The Federal Circuit looked to the intrinsic evidence, and in spite of the ordinary meaning of the term, noted that throughout the specification “human antibodies” would encompass both fully human and “humanized” antibodies. The Court then noted the prosecution history of the patent, much of which indicated that “human antibodies” encompassed both fully human and “humanized” antibodies. The patentee initially filed claims for “antibodies” and after amending that term, the patent examiner expressly wrote in a post-amendment office action that “human antibodies” included “humanized” antibodies, which the patentee did not object to.

Finally, the Court noted that while the extrinsic evidence given by the patentee may suggest that “human antibodies” do not contain both fully human and “humanized” antibodies, that such evidence does not outweigh the strong intrinsic evidence suggesting otherwise. As such, the Court agreed with the Board’s claim construction and affirmed the finding of patent invalidity.