Written Description and Enablement Requirements For Antibodies

By Irving Feit

Teva Pharmaceuticals International GmbH v. Eli Lilly and Company

U.S. Court of Appeals for the Federal Circuit

Case Number 2024-109

Decided: April 16, 2026

The Law

The written description and enablement requirements for all inventions must satisfy 35 U.S.C. §112, which states in relevant part:

The specification shall contain a written description of the invention, and of the manner and process of making and using it, in such full, clear, concise, and exact terms as to enable any person skilled in the art to which it pertains, or with which it is most nearly connected, to make and use the same…

This provision contains two separate requirements: written description and enablement. In practice, however, as noted by the Federal Circuit in the Teva case,: “Enablement and written description often rise and fall together…So it is here.” See the first sentence in Section II on page 21.

Teva’s Patent

The claim at issue in the Teva case is directed to a method of treating headaches, including migraine headaches, in human patients. The claimed method requires administering a humanized anti-CGRP monoclonal antibody. Increased levels of the neurotransmitter CGRP (calcitonin gene-related peptide) are known to cause migraine headaches by, inter alia, severe sensitization of pain nerves.

Teva’s specification disclosed several murine anti-CGRP antagonist antibodies, but just one humanized version. The specification also disclosed methods of making and humanizing antibodies, and reported that both making and humanizing antibodies were routine. See the paragraph bridging pages 13 and 14 of the Teva decision.

The Trial

Teva sued Eli Lilly in the District Court for the District of Massachusetts for infringement of its patent. At the trial, a jury found that Eli Lilly had not proven Teva’s patent to be invalid and had willfully infringed the patent. See the penultimate paragraph on page 5.

However, the district court judge overruled the jury and granted Eli Lilly’s motion for judgment as a matter of law (“JMOL”). According to the district court judge, the disputed claim in Teva’s patent was clearly invalid for failure to satisfy both the written-description and enablement requirements of 35 U.S.C. §112. Teva appealed the decision to the Federal Circuit. See the paragraph bridging pages 5 and 6.

The Appeal

On appeal, the Federal Circuit considered the following four facts to be important:

1. Anti-CGRP antagonist antibodies and methods of making them were already well known.
2. Humanizing the antibodies would have been routine.
3. Humanized antibodies per se are not claimed. The claim recited a method of treating a specific medical condition.
4. The specification disclosed that all humanized antibodies work for the claimed method of treating headaches.

See the paragraph bridging pages 22 and 23.

The Federal Circuit considered fact 3 to be particularly important, i.e., Teva’s claim recited a method of using antibodies, and not antibodies per se. See the first sentence of the full paragraph on page 22. (“… Lilly’s argument [for insufficient written description] might be more persuasive if the asserted claims were to the genus of humanized anti-CGRP antagonist antibodies themselves.”

The Federal Circuit also considered fact 4 to be important. See the paragraph bridging pages 22 and 23 (“… the specification disclosed that all such antibodies work for that purpose.” Emphasis in original.).

By emphasizing facts 3 and 4, the Federal Circuit was able to conclude that Teva’s specification disclosed the requisite “representative number of species” of humanized anti-CGRP antagonist antibodies so support the breadth of the antibodies used in the claimed method. See the paragraph bridging pages 13 and 14, which states:

And, critically, a skilled artisan would have understood from the specification that all humanized anti-CGRP antagonist antibodies treat headache. The jury therefore could have reasonably found that the specification disclosed a representative number of species of humanized anti-CGRP antagonist antibodies for purposes of the claimed invention, thus rendering JMOL of no written description improper.

Later in its decision, the Federal Circuit further explained that the scope of the disputed claim was limited to humanized anti-CGRP antagonist antibodies that treat headache. See the paragraph bridging pages 22 and 23.

For the reasons above, the Federal Circuit reversed the district court’s JMOL regarding written description and enablement, and remanded the case back to the district court for further proceedings consistent with its opinion.

Practice Tips

In order to obtain patent protection for antibodies, claims should recite methods to treat specific method conditions. If, as in the Teva case, it is possible to state that all anti-antigen antibodies are effective in the claimed method, it will be important to do so. Otherwise, it will be important to state as much as possible about determining which antibodies are expected to be effective in the claimed method, and which are not.

Conclusion

Before the Teva decision, claims to methods of treating specific medical conditions with an antibody required reciting a specific antibody. By following the above practice tips, it may now be possible to claim methods of treating specific medical conditions with a genus of antibodies. Such claims are significantly broader than claims to methods of treating medical conditions previously thought possible.

Please note: as I read the Teva decision, I had the impression that the primary purpose of the Federal Circuit was to address the harshness of earlier Federal Circuit and Supreme Court decisions, in particular Amgen Inc. v. Sanofi, 987 F.3d 1080, (Fed. Cir. 2021) (cleaned up), aff’d, 598 U.S. 594 (2023). The Amgen decision has been much criticized.

In the Amgen case, the claims recited a genus of antibodies, per se, with certain binding and neutralizing characteristics. The specification disclosed amino acid sequences for 26 specific antibodies that had the requisite characteristics.

However, the 26 specific antibody sequences were not enough. According to the U.S. Supreme Court, “Amgen has failed to enable all that it has claimed.” Amgen, Inc. 598 U.S at 613. Therefore, Amgen’s application was declared invalid for lack of enablement.

I found the rational of the Teva decision a little hard to follow. Therefore, it may be more important to try to take advantage of the decision than to try to understand the logic of it.