Writing for a three-judge panel, Circuit Judge Sharon Prost held that U.S. District Judge Allison Dale Burroughs was wrong to grant judgment as a matter of law that the asserted claims of Teva's '045, '907, and '908 patents failed the written-description and enablement requirements of 35 U.S.C. § 112. The panel remanded for further proceedings.

The jury in the District of Massachusetts had found that Lilly willfully infringed the patents and had failed to prove the claims invalid. Judge Burroughs set that verdict aside on JMOL. The Federal Circuit applied First Circuit law and reviewed the ruling de novo.

Prost wrote that a reasonable jury could have found that by the November 2006 priority date, anti-CGRP antagonist antibodies and methods of making them were already well known, and humanization was a routine procedure. The panel cited Lilly's own statements from earlier inter partes review proceedings, where Lilly had maintained that the prior art was "replete with exemplary disclosures of anti-CGRP antagonist antibodies" and that humanization "was a well-established and routine procedure" by that date.

The claims at issue, the panel said, are not directed to the antibodies themselves but to the method of using them to treat headache. That distinction put the case in a line of precedent including Ajinomoto and In re Herschler, which concern "a well-known genus used as part of a different invention." A skilled artisan, Prost wrote, would have understood from the specification that "all humanized anti-CGRP antagonist antibodies" treat headache.

The panel rejected Lilly's argument — drawn from University of Rochester v. G.D. Searle — that the distinction between claims to methods and claims to the antibodies is a "semantic distinction without a difference." Prost said Rochester and Ariad are distinguishable because in those cases the compounds used in the claimed methods were neither disclosed nor known in the art, while here "anti-CGRP antagonist antibodies were well known in the prior art and disclosed in the specification."

On enablement, the panel noted that enablement and written description "often rise and fall together." Prost distinguished the Supreme Court's decision in Amgen v. Sanofi and the Federal Circuit's ruling in Baxalta v. Genentech, both of which involved claims to entire antibody genera. Because Teva's claims cover only the use of the antibodies to treat headache, and because the specification disclosed that all humanized anti-CGRP antagonist antibodies work for that purpose, the panel said any further work to find or make additional antibodies would be "more akin to extra credit than a necessary research assignment left to others to complete."

The panel also addressed Lilly's argument, drawn from AbbVie Deutschland v. Janssen Biotech, that representativeness requires disclosure of an antibody structurally similar to the accused product. Prost wrote that AbbVie did not set forth "a bright-line, always-applicable rule" and did not involve a well-known genus used as part of a different invention.

G1, the sole humanized anti-CGRP antagonist antibody disclosed in the specification, is the active ingredient in Teva's Ajovy product. Teva brought suit in September 2018 alleging indirect infringement through Lilly's Emgality. Lilly's conditional cross-appeal on damages was voluntarily dismissed in September 2025.

Circuit Judge Tiffany Cunningham and District Judge Richard G. Andrews, sitting by designation from the District of Delaware, joined the opinion. Kevin P. Martin of Goodwin Procter argued for Teva. William Barrett Raich of Finnegan Henderson Farabow Garrett & Dunner argued for Lilly. Costs were awarded to Teva.