Functional Claim Limitations Pose High Hurdles for Fulfilment of Enablement Requirements

  • April 27, 2021

By: Gregory K. Gerstenzang

Amgen Inc. v. Sanofi, 2020-1074 (Fed. Cir. Feb. 11, 2021)

In Amgen, The Federal Circuit held that Amgen’s double-function claims were invalid for lack of enablement, on the grounds that the specification, which contained only narrowly disclosed examples, was not enabling for the full claim scope without undue experimentation.

(This is an appeal following the district court’s decision on remand from the Federal Circuit. For discussion of the Federal Circuit’s decision during the first appeal, click here.)

Amgen sued a collection of pharmaceutical companies, including Sanofi, for infringement of two patents directed to antibodies useful for lowering LDL levels by purportedly blocking binding of PCSK9 to LDL receptors. The claimed antibodies were characterized by functional properties, such as specifying particular residues of PCSK9 to which the antibody binds and requiring partial or full blocking of the interaction between PCSK9 and LDLR, and not structural characteristics, for example, the amino acid sequences of binding domains.

Following an initial trial and appeal to the Federal Circuit, the case was remanded due to errors in evidentiary rulings and jury instructions. On remand, the district court granted Sanofi’s motion for judgment as a matter of law that Amgen’s asserted claims were invalid for lack of enablement. Amgen appealed to the Federal Circuit.

The enablement requirement states that the specification shall enable any person skilled in the art to make and use the patented invention. To show that a claim is invalid for lack of enablement, a challenger must show by clear and convincing evidence that one of skill in the art would not be able to practice the claimed invention without undue experimentation.

The Federal Circuit disagreed with Amgen. The court emphasized that functional claim limitations are not precluded but the inclusion of broad functional language within a claim may raise the bar for enablement. The court also noted that while the specification need not describe how to make and use every possible variant of the claimed invention, an enablement analysis involves considering the quantity of experimentation necessary to practice the full scope of a claim. Further, while the effort need not be that which is required to exhaust a genus, it is appropriate to determine the effort necessary to obtain embodiments outside the scope of the disclosed examples and guidance. When the specification provides limited working examples, the art is unpredictable, and practicing the full scope of the claimed invention requires the synthesis and screening of a large number of possible candidates, the court has generally found that practicing the claimed invention requires undue experimentation and that the claims lack enablement.

Ultimately, the Federal Circuit held that the specification was not enabling for the full scope of the double-function claims without undue experimentation by one of skill in the art, because practicing the claimed invention would require the synthesis and screening of a large number of possible candidates. The claims were broader than the narrow disclosed examples and encompassed millions of potential candidate antibodies, which would need to be generated and tested before it could be determined whether the candidates were encompassed by the claimed invention.

Key Takeaway:

Broad functional limitations in an antibody claim can make complying with the enablement requirement challenging. Proper enablement analysis involves consideration of the quantity of experimentation required to practice the full scope of the claim, not simply the number of embodiments encompassed by a claim.


How can we help you?