Amgen, Inc. (“Amgen”) sued Sanofi (“Sanofi”) for infringement of a patent on monoclonal antibodies that are useful in reducing levels of LDL cholesterol. An example claim read: “An isolated monoclonal antibody, wherein, when bound to [the protein], the monoclonal antibody binds to at least one of the following residues: [list of residues], and wherein the monoclonal antibody blocks binding of [the protein] to [LDL receptors].” The parties stipulated to infringement, and tried their invalidity case before a jury. The jury found the claims were enabled and did not lack written description support, and the district court granted judgment of non-obviousness and no willfulness. Sanofi appealed, and the Federal Circuit reversed the jury verdict due to various errors in evidentiary rulings and jury instructions. The trial court then held a new trial on enablement and written description.

In the new trial, Amgen argued that the claims were enabled because no undue experimentation was required to obtain antibodies with the claimed functional properties. The specification described a screening method for identifying whether an antibody met the claimed functional requirements, and further described representative antibody structures. Thus, Amgen argued the full scope of the claim was enabled.

Sanofi disagreed. It argued that there were millions of possible candidate antibodies, and applying the screening method to every candidate to determine whether it had the required functional characteristics would amount to undue experimentation. Sanofi argued that such a process would amount to “trial and error,” and finding such an antibody would be itself a de novo discovery. Further, merely identifying a few representative embodiments that fit the functional criteria was inadequate to enable the full scope of the claims.

The jury again found that the claims were enabled and supported by the written description; however, the district court granted a motion for judgment as a matter of law that the claims were not enabled, and therefore invalid. Amgen appealed.

The Federal Circuit affirmed the district court’s ruling that the claims were not enabled. The Federal Circuit reasoned that enablement turns on “the quantity of experimentation that would be required to make and use, not only the limited number of embodiments that the patent discloses, but also the full scope of the claim.” The court warned that functional limitations “pose high hurdles in fulfilling the enablement requirement for claims with broad functional language.” To show lack of enablement, a defendant did not need to prove that undue experimentation would be required to exhaust the entire scope of the claim, but only that it would take undue experimentation to obtain embodiments claimed but not specifically described. The Federal Circuit found that that standard was met here, and thus the claims were invalid for lack of enablement.

What This Means For You

This case is a warning to patent prosecutors that use functional language when claiming inventions in fields where outcomes can be unpredictable (e.g., biotechnology and chemistry). According to the Federal Circuit, even the disclosure of a screening technique for identifying other embodiments is insufficient to show a claim is enabled. Thus, functional language should be used carefully and sparingly to prevent this kind of analysis from rendering claims invalid. For defenders of patent infringement claims, this case may provide another vector of attack for an invalidity defense.