. . . because single chain antibody variants number in the “millions of billions,” . . . the disclosure of only two working embodiments fails to distinguish the single chain antibodies that exhibit the claimed function from those that do not. . . .

In Juno Therapeutics, Inc. v. Kite Pharma, Inc., No. 2020-1758 (Fed. Cir. August 26, 2021), the Court of Appeals for the Federal Circuit overturned a $1.2 billion damages award against Kite by invalidating the underlying patent claims for lack of written description in support of certain claim elements. The patent claims are directed to T-cells reprogrammed with “chimeric antigen receptors” (so-called “CAR T-cells”) that set the modified T-cells on search and destroy missions, targeting malignant cells that express the receptor-matching antigen. The infringement accusations in the case focused on a CAR T immunotherapy, YESCARTA®, developed by Kite that reprograms a patient’s own T-cells to kill B-cell lymphomas and leukemias.

Independent claim 1 of the asserted patent, U.S. Patent No. 7,440,190, is directed to a nucleic acid polymer encoding a chimeric T cell receptor that, among other things, has “a binding element that specifically interacts with a selected target.” Certain dependent claims specify an “antibody” as the binding element, and other dependent claims specify an antibody derivative or “single chain antibody” as the binding element. The patent’s specification identifies two types of single chain antibodies.

The first is a single chain antibody derived from the “J591 antibody” that binds the PSMA protein on the surface of prostate cancer cells. The second is a single chain antibody derived from the “SJ25C1 antibody” that binds the CD19 protein on the surface of B-cell lymphoma cells. Each of two dependent claims of the patent requires a single chain antibody that “binds to CD19.” These two claims read on the reprogrammed cells in Kite’s YESCARTA® B-cell lymphoma and leukemia immunotherapy.

Despite the disclosure of two working embodiments of the invention, Kite challenged the written description support for the single chain antibody claim elements. Kite emphasized that the claims specify the single chain antibody, not by structure, but instead by function, for example, “wherein the single chain antibody binds to CD19.” And, because single chain antibody variants number in the “millions of billions,” Kite argued that the disclosure of only two working embodiments fails to distinguish the single chain antibodies that exhibit the claimed function from those that do not.

The Federal Circuit agreed with Kite, adding that the patent’s “written description contains scant details about which [single chain antibodies] can bind which target antigens.” Id. at 9. The court minimized the two disclosed embodiments as disclosing “no details about these [single chain antibody] species beyond the alphanumeric designations J591 and SJ25C1,” such as information identifying the nucleotide sequences that express the single chain antibodies or their structures. Id. at 9-10.

The Federal Circuit explained that “[f]or genus claims using functional language, like the binding function of the [single chain antibodies] claimed here, the written description ‘must demonstrate that the applicant has made a generic invention that achieves the claimed result and do so by showing that the applicant has invented species sufficient to support a claim to the functionally-defined genus.’” Id. at 7 (quoting Ariad Pharms, Inc. v. Eli Lilly & Co., 598 F.3d 1336, 1352 (Fed. Cir. 2010) (en banc)). The court emphasized that “a genus can be sufficiently disclosed by ‘either a representative number of species falling within the scope of the genus or structural features common to the members of the genus so that one of skill in the art can ‘visualize or recognize’ the members of the genus.’” Id. (quoting Ariad, 598 F.3d at 1352).

The court therefore rejected the patent owner’s expert testimony that that the two disclosed embodiments of the invention are sufficiently representative of the claimed genus “because [single chain antibodies] all do the same thing. They bind to the antigen.” Id. at 10 (quoting J.A. 33945). The court said that the testimony failed to “explain[] which [single chain antibodies] will bind to which targets” and that “the mere fact that [single chain antibodies] in general bind does not demonstrate that the inventors were in possession of the claimed invention.” Id.

The Federal Circuit stressed that “the purpose of the written description requirement is to ensure that the scope of the right to exclude . . . does not overreach the scope of the inventor’s contribution to the field of art as described in the patent specification.” Id. (quoting Ariad, 598 F.3d at 1353-54). The court therefore concluded that “[t]he disclosure of one [single chain antibody] that binds to CD19 and one [single chain antibody] that binds to a PSMA antigen . . . does not provide information sufficient to establish that a skilled artisan would understand how to identify the species . . . capable of binding to the limitless number of targets as the claims require.” Id. at 9-10.

This decision is one of a growing number of cases demanding heightened attention to the written description requirement, especially where the patent claims are drawn to a broad genus in an unpredictable art. For example, in Idenix, the Federal Circuit invalidated claims specifying nucleosides active against a hepatitis C virus because the patent merely provided “lists or examples of supposedly effective nucleosides, but [did] not explain what makes them effective, or why.” Idenix Pharms. LLC v. Gilead Scis. Inc., 941 F.3d 1149, 1164 (Fed. Cir. 2019). Likewise, in AbbVie, the Federal Circuit affirmed the invalidation of claims to “every fully human IL-12 [targeted] antibody that would achieve a desired result” where the patent specification provided a structural description of only one antibody species. AbbVie Deutschland GmbH v. Janssen Biotech, Inc., 759 F.3d 1285, 1301-02 (Fed. Cir. 2014).

These and other cases demonstrate the potential folly of relying on a handful of exemplary embodiments together with an assumed common understanding of skilled artisans to satisfy the written description requirement. Cautious patent drafters will provide structural and other descriptions of the embodiments to demonstrate both a representation of the claimed invention and the inventor’s possession of the full scope of the invention.