Beware Enablement of Genus Antibody Claims

By on October 5, 2023
Posted In Patents

The US Court of Appeals for the Federal Circuit invalidated yet another set of antibody genus claims, finding the case “materially indistinguishable” from those in the 2023 Supreme Court of the United States case, Amgen v. Sanofi. The Federal Circuit concluded that patent claims covering a class of antibodies targeting functions of blood clotting factors were invalid for lack of enablement, echoing the reasoning followed by fellow Circuit Judge Dyk, who sat by designation in the district court. Baxalta Inc. and Baxalta GMBH v. Genentech, Inc., Case No. 2022-1461 (Fed. Cir. Sept. 20, 2023) (Moore, Clevenger, Chen, JJ.)

This case involves Baxalta’s patent covering antibody preparations that bind to blood clotting Factors IX/IXa and thereby increase the procoagulant activity of Factor IXa. This in turn activates another blood clotting factor, Factor X, that is useful to treat hemophilia, particularly in patients who develop inhibitors to blood clotting Factor VIII. The claim at issue recited “[a]n isolated antibody or antibody fragment thereof that binds Factor IX or Factor IXa and increases procoagulant activity of Factor IXa.”

Baxalta sued Genentech for infringement. In a prior appeal involving claim construction, the Federal Circuit vacated the district court’s grant of summary judgment of noninfringement and remanded for further proceedings. On remand, the district court granted Genentech’s motion for summary judgment for lack of enablement. Baxalta appealed.

Baxalta challenged the summary judgment of invalidity on enablement. Baxalta argued that a skilled artisan could make the full scope of the claimed antibodies without undue experimentation. With reference to the subject patent’s disclosure of using a prior art method known as the hybridoma technique for generating Factors IX/IXa antibodies, Baxalta argued that using routine screenings to find the antibodies exhibiting the claimed functions (i.e., those that bind Factors IX/IXa and increase procoagulant activity of Factor IXa) was within the skill of a skilled artisan without undue experimentation.

The Federal Circuit, citing Amgen, explained that the enablement standard under Section 112(a) requires that “the specification [] enable the full scope of the invention as defined by its claims,” allowing for “a reasonable amount of experimentation.” The Court explained that in Amgen, the patents at issue generically claimed all antibodies that bind to specific amino acid residues on a protein and blocked the protein from binding to LDL receptors. The Court observed that while the Amgen patent disclosed amino acid sequences of 26 antibodies, the claim scope could cover millions. Similarly, the Amgen patent disclosed a roadmap and another conservative substitution method for generating new antibodies and testing them for the claimed functions. In Amgen, the Supreme Court held that such methods were nothing more than “trial-and-error experimentation,” which, in the absence of “some general quality . . . running through the class that gives it a peculiar fitness for the particular purpose,” failed to enable the full scope in that case.

The Federal Circuit found the facts in this case “materially indistinguishable” from Amgen. Like the claims at issue in Amgen, Baxalta’s patent claims all antibodies that meet the claimed functions. The Court also found that while the patent specification discloses amino acid sequences of 11 exemplary antibodies, the claim scope here, as in Amgen, could also cover millions of antibodies. Finally, drawing parallels with the Amgen patents’ roadmap, the Court concluded that the patent’s hybridoma-and-screening method involved the same trial-and-error process that led to the discovery of the 11 disclosed antibodies. Additionally, the Court found no disclosures of common structural features linked to the claimed function that would allow a skilled artisan to predict which antibodies would perform the claimed function without the need for a trial-and-error process. According to the Court, such “random trial-and-error” experimentation, without more, is per se unreasonable under Amgen. The Court further clarified that Amgen does not alter the In re Wands standard for enablement.

Accordingly, the Court affirmed the district court’s grant of summary judgment for invalidity for lack of enablement.

Practice Note: Patent prosecution practitioners should consider layering claim scope for genus or functional claims, including adding picture claims and claims closely supported by working examples that demonstrate common structural elements that predict function. Litigators should carefully consider the range of claim scope and how the file history could limit or broaden the scope during claim construction. A special emphasis should be given to the interplay between asserted defenses for obviousness/anticipation and enablement.

Jayita Guhaniyogi, PhD
Jayita Guhaniyogi, PhD focuses her practice on patent litigation with an emphasis in the chemical, life sciences and pharmaceutical industries. She handles patent infringement litigation cases and provides general counseling on patent-related issues. Her experience spans all stages of patent litigation, including pre-suit investigations, fact and expert discovery, motion practice, claim construction, trial and appeal. Read Jayita Guhaniyogi's full bio.