The opinion in Teva Pharms. Int’l GMBH v. Eli Lilly & Co., No. 24-1094 (Fed. Cir. April 16, 2026) creates a distinction for written description and enablement under 35 U.S.C. §112(a) when the claims in dispute are method-of-use claims versus article claims. This case also serves as a cautionary tale of the inherent tension when first arguing that a claim is obvious and then arguing that the claim lacks written description and/or enablement.
Teva held article patents directed to humanized anti-CGRP antagonist antibodies (the “antibody patents”) and method-of-use patents directed to treating headaches using humanized anti-CGRP antagonist antibodies (the “headache patents”). In both sets of patents, Teva disclosed several murine (in mice) anti-CGRP antagonist antibodies and disclosed that humanizing murine antibodies was routine at the time the patents were filed. However, Teva’s patents only disclosed one humanized anti-CGRP antagonist antibody, which was the antibody used in Teva’s headache medicine. Notably, Eli Lilly’s headache medicine did not use the same humanized anti-CGRP antagonist antibody as Teva’s headache medicine.
Eli Lilly challenged Teva’s patents via inter partes review (IPR) and asserted that at the time Teva filed its applications murine anti-CGRP antagonist antibodies were “well known in the art” and the prior art was “replete with exemplary disclosures of anti-CGRP antagonist antibodies.” Teva v. Eli Lilly at 4.Eli Lilly further asserted that humanizing murine antibodies “was well-established and routine procedure.” Id.The Patent Trial and Appeal Board (PTAB) agreed and held that the antibody patents (i.e., article patents) were not patentable. However, the PTAB did not agree with Eli Lilly as to Teva’s method-of-use headache patents and upheld those patents.
Defending against infringement of Teva’s headache patents at the district court, Eli Lilly argued that Teva’s headache patents were invalid under 35 U.S.C. §112 for lacking written description and/or enablement. A jury found that Teva’s headache patents were not invalid and that Eli Lilly infringed the headache patents. In response, Eli Lilly filed a motion for judgment as a matter of law (JMOL) as to the lack of written description and/or enablement of Teva’s headache patents, which the district court granted. Teva appealed the JMOL to the Court of Appeals for the Federal Circuit.
“For claims to a genus, adequate written description requires disclosure of ‘either a representative number of species falling within the scope of the genus or structural features common to the members of the genus so that one of skill in the art can visualize of recognize the members of the genus.’” Teva v. Eli Lilly at 8 (citing Ariad Pharms., Inc. v. Eli Lilly & Co., 598 F.3d 1336, 1350 (Fed Cir. 2010) (en banc)). Eli Lilly argued that Teva’s disclosure of one humanized anti-CGRP antagonist antibody in its specification did not meet this standard, claiming there are thousands of murine anti-CGRP antagonist antibodies and Teva did not disclose a “representative number of species” citing the Supreme Court’s opinion in Amgen Inc. v. Sanofi, 598 U.S. 594 (2023). Moreover, as to enablement, Eli Lilly argued that undue experimentation would be required to find and humanize the entire genus of anti-CGRP antagonist antibodies recited in the claims.
Although the Federal Circuit did not address written description or enablement of Teva’s antibody patents—they were not at issue in the appeal—the court did make a distinction between the antibody patents and the headache patents stating, “[t]he headache patents make clear that their claimed invention is the use of anti-CGRP antagonist antibodies … to treat headache—not such antibodies themselves.” Teva v. Eli Lilly at 12 (emphasis original). As to enablement, the Federal Circuit noted, “[t]he asserted claims here are unlike the claims in Amgen … because they do not claim humanized anti-CGRP antagonist antibodies themselves; instead, the claim only the use of such antibodies for the different, limited purpose of treating headache.” Id. at 22–23 (emphasis original).
Using this distinction, the Federal Circuit favorably cited a precedential opinion that “repeatedly distinguished between claims to a genus itself (particularly a novel one) … and claims that … concerned a known genus as part of a different invention.” Teva v. Eli Lilly at 10 (emphasis original) (citing In re Herschler, 591 F.2d 693 (CCPA 1979). Claims to a “different invention” do not need to describe a known genus in the same specificity as claims directed to the genus itself. Here, the Federal Circuit determined that Teva’s headache patents fell into this category of “different invention” from the antibody genus itself and therefore needed to only evaluate whether the genus of humanized anti-CGRP antagonist antibodies recited in Teva’s claims was sufficiently known.
In determining whether the genus of humanized anti-CGRP antagonist antibodies was known, the Federal Circuit cited the arguments that Eli Lilly presented to assert that Teva’s claims were obvious. Particularly, the Federal Circuit noted that murine anti-CGRP antagonist antibodies were “well known in the art” and the prior art was “replete with exemplary disclosures of anti-CGRP antagonist antibodies,” as Eli Lilly argued. Moreover, the Federal Circuit found that humanizing murine anti-CGRP antagonist antibodies “was well-established and routine procedure” at the time Teva’s applications were filed. So, the only issue remaining was whether undue experimentation was required to figure out which humanized anti-CGRP antagonist antibodies could treat headaches. The Federal Circuit found that in the motion for JMOL Eli Lilly acquiesced that from Teva’s specification a skilled artisan could understand that any anti-CGRP antagonist antibody could be used to treat headaches, thus no experimentation is needed to determine whether any one anti-CGRP antagonist antibody treats headaches. Accordingly, the Federal Circuit reversed the JMOL.
Key takeaways include:
- Have a diversified claim strategy that includes article (antibody) claims, method claims, and method-of-use claims—especially when claiming a genus—because each class of claims may be evaluated differently.
- When developing a litigation strategy, it is important to recognize that there is a necessary tension between arguing that a claim is obvious and also arguing that the claim lacks written description and/or is not enabled and one must walk the line between these two arguments with significant consideration.
Should you have any questions about this case or implications, please contact your Dinsmore intellectual property attorney.