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Beware Enablement of Genus Antibody Claims

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 [...]

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Another Genus Claim Bites the Dust for Lack of Written Description

Addressing the issue of written description in the context of antibody-related genus claims, the US Court of Appeals for the Federal Circuit reversed a $1.2 billion jury verdict and found genus claims using functional language invalid for lack of written description. Juno Therapeutics, Inc. v. Kite Pharma, Inc., Case No. 20-1758 (Fed. Cir. Aug. 26, 2021) (Moore, J.)

Kite’s YESCARTA® is a therapy in which a patient’s T cells are engineered to express a chimeric antigen receptor (CAR) to target the antigen CD19. Juno sued Kite, alleging infringement of a patent relating to a nucleic acid polymer encoding a three-part CAR for a T cell. The three-part CAR comprises:

  1. An intracellular domain of the CD3 ζ (zeta) chain, a signaling domain that is activated to create an initial immune response
  2. A costimulatory region comprising of a specific amino acid sequence (here, a specific CD28 sequence) that, when activated, directs the T cells to multiply
  3. A binding element that determines what target molecule or antigen the CAR can bind to, such as a single-chain antibody variable fragment (scFV).

Juno’s patent disclosed two scFVs (one that binds CD19 and another that binds PSMA) but did not disclose the amino acid sequence of either scFV.

After a two-week trial, the jury reached a verdict in Juno’s favor, finding in relevant part that Kite failed to prove that any of the asserted claims were invalid for lack of written description or enablement. The jury awarded damages amounting to a $585 million upfront payment and an almost 28% running royalty. The district court denied Kite’s motions for judgment as a matter of law and enhanced the total award to approximately $1.2 billion in addition to the 28% running royalty. Kite appealed.

The Federal Circuit reversed, concluding that no reasonable jury could find adequate written description because the patent disclosed neither representative species nor common structural features of the claimed scFV genus to identify which of the millions of billions of scFVs would function as claimed. Turning first to lack of representative species, the Court explained that the broadest asserted claims cover any scFV that binds to any target of clinical interest but fails to provide a representative sample of species within, or defining characteristics for, that expansive genus. The Court also disagreed that the two working embodiments in the patent were representative of the entire genus of vast number of possible scFVs that bind to an undetermined number of targets without more in the disclosure (such as the characteristics of the exemplary scFVs that allow them to bind to particular targets or nucleotide sequences). The Court stated that even if such scFVs were known as Juno argued, the specification provided no means of distinguishing which scFVs would bind to which targets.

Turning next to lack of structural features common to the claimed genus, the Federal Circuit held that general assertions that scFVs generally have a common structure in the context of the technology in this case were insufficient because an scFV with the [...]

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