Court Opinion

ID: 4878933
Source: CourtListenerOpinion
Date Created: 2021-08-26 15:03:19.859403+00
Date Added: 2024-06-11T08:12:37.201579
License: Public Domain

Case: 20-1758   Document: 75     Page: 1   Filed: 08/26/2021

   United States Court of Appeals
       for the Federal Circuit
                 ______________________

 JUNO THERAPEUTICS, INC., SLOAN KETTERING
     INSTITUTE FOR CANCER RESEARCH,
              Plaintiffs-Appellees

                            v.

                 KITE PHARMA, INC.,
                  Defendant-Appellant
                 ______________________

                       2020-1758
                 ______________________

    Appeal from the United States District Court for the
 Central District of California in No. 2:17-cv-07639-PSG-
 KS, Judge Philip S. Gutierrez.
                  ______________________

                Decided: August 26, 2021
                 ______________________

     MORGAN CHU, Irell & Manella LLP, Los Angeles, CA,
 argued for plaintiffs-appellees. Also represented by ALAN
 J. HEINRICH, ELIZABETH C. TUAN; GREGORY A. CASTANIAS,
 JENNIFER L. SWIZE, Jones Day, Washington, DC; LISA LYNN
 FURBY, Chicago, IL; ANDREA WEISS JEFFRIES, Los Angeles,
 CA; MATTHEW J. RUBENSTEIN, Minneapolis, MN.

     E. JOSHUA ROSENKRANZ, Orrick, Herrington & Sutcliffe
 LLP, New York, NY, argued for defendant-appellant. Also
 represented by MELANIE L. BOSTWICK, ROBBIE MANHAS,
 JEREMY PETERMAN, Washington, DC; GEOFFREY DONOVAN
Case: 20-1758     Document: 75     Page: 2    Filed: 08/26/2021

 2               JUNO THERAPEUTICS, INC.   v. KITE PHARMA, INC.

 BIEGLER, Fish & Richardson, San Diego, CA; TED G. DANE,
 PETER GRATZINGER, ADAM R. LAWTON, GARTH VINCENT,
 JEFFREY I. WEINBERGER, Munger, Tolles & Olson LLP, Los
 Angeles, CA.
                 ______________________

 Before MOORE, Chief Judge, PROST and O’MALLEY, Circuit
                        Judges.
 MOORE, Chief Judge.
     Kite Pharma, Inc. appeals a final judgment of the
 United States District Court for the Central District of Cal-
 ifornia that (1) claims 3, 5, 9, and 11 of U.S. Patent No.
 7,446,190 are not invalid for lack of written description or
 enablement, (2) the ’190 patent’s certificate of correction is
 not invalid, and (3) Juno Therapeutics, Inc., and Sloan Ket-
 tering Institute for Cancer Research (collectively, Juno)
 were entitled to $1,200,322,551.50 in damages. Juno Ther-
 apeutics, Inc. v. Kite Pharma, Inc., No. 2:17-cv-07639-PSG-
 KS, (C.D. Cal. April 8, 2020), ECF 728. Because we con-
 clude that the jury verdict regarding written description is
 not supported by substantial evidence, we reverse.
                        BACKGROUND
      T cells are white blood cells that contribute to the
 body’s immune response. J.A. 32906–07. They have natu-
 rally occurring receptors on their surfaces that facilitate
 their attack on target cells (such as cancer cells) by recog-
 nizing and binding an antigen, i.e., a structure on a target
 cell’s surface. J.A. 32907–08.
     Chimeric antigen receptor (CAR) T-cell therapy in-
 volves isolating a patient’s T cells; reprogramming those
 T cells to produce a specific, targeted receptor (a CAR) on
 each T cell’s surface; and infusing the patient with the re-
 programmed cells. J.A. 32913; ’190 patent at 2:31–36,
 7:24–33. The reprogramming involves introducing genetic
 material containing a nucleotide sequence encoding for a
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 JUNO THERAPEUTICS, INC.   v. KITE PHARMA, INC.                 3

 CAR into the T cell so that the cell produces the CAR on its
 surface. J.A. 32913; ’190 patent at 1:30–34, 2:27–36. This
 CAR allows the T cell to recognize the specific antigen for
 which it was programmed. J.A. 32913; ’190 patent at 2:27–
 36.
      The ’190 patent relates to a nucleic acid polymer encod-
 ing a three-part CAR for a T cell. It claims priority to a
 provisional application filed May 28, 2002, a time period
 that one of the inventors labeled as “the birth of the CAR-
 T field.” J.A. 32976. The first portion of the three-part
 CAR is called the intracellular domain of the human CD3 ζ
 (zeta) chain. See, e.g., ’190 patent at 2:14–16, 4:12–17. It
 is a signaling domain that, when the T cell binds to an an-
 tigen, is activated to create an initial immune response.
 J.A. 103. The second portion is a costimulatory region com-
 prising a specific amino acid sequence (SEQ ID NO:6) that
 is part of a naturally occurring T-cell protein called CD28.
 ’190 patent at 2:16–17, 3:44–54. When activated, the cost-
 imulatory region creates a second signal to augment or pro-
 long the immune response by, for example, directing the
 T cells to multiply. J.A. 103; J.A. 32912. The CD3-zeta
 portion and the costimulatory region combine to make a
 signaling element, or backbone, of the CAR. J.A. 32906;
 J.A. 32912–13. This combination of the CD3-zeta and cost-
 imulatory regions allows the T cells to not only kill target
 cells but also to divide into more T cells. J.A. 32913–14.
 The third and final portion of the ’190 patent’s CAR is the
 binding element, which is the portion of the CAR that de-
 termines what target molecule or antigen the CAR can rec-
 ognize and bind to. ’190 patent at 4:34–45; J.A. 32912–13.
     One type of binding element in the ’190 patent is a sin-
 gle-chain antibody, i.e., a single-chain antibody variable
 fragment (scFv).      ’190 patent at 4:52–57; see also
 J.A. 32910. An scFv is made by taking two pieces of an
 antibody, one from the heavy chain of an antibody’s varia-
 ble region and one from the light chain of an antibody’s var-
 iable region, and linking them together with a linker
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 4               JUNO THERAPEUTICS, INC.   v. KITE PHARMA, INC.

 sequence. J.A. 32908–09; see also J.A. 2643–44; J.A. 103;
 ’190 patent at 4:52–5:5. Each variable region has a unique
 amino acid sequence that can dictate whether and how an
 antibody, and thus an scFv, binds to a target. J.A. 2643;
 J.A. 103. The ’190 patent discloses two scFvs. One of those
 scFvs is derived from the SJ25C1 antibody and binds
 CD19, a protein that appears on the surface of diffuse large
 B-cell lymphoma cells. ’190 patent at 11:12–22; see also
 J.A. 58. The other disclosed scFv is derived from the J591
 antibody and binds PSMA, a protein that appears on the
 surface of prostate cancer cells. ’190 patent at 7:43–51,
 8:5–10; see also J.A. 32967; J.A. 33945. The ’190 patent
 does not disclose the amino acid sequence of either scFv.
     Independent claim 1 of the ’190 patent recites:
     1. A nucleic acid polymer encoding a chimeric T cell
     receptor, said chimeric T cell receptor comprising
         (a) a zeta chain portion comprising the in-
         tracellular domain of human CD3 ζ chain,
         (b) a costimulatory signaling region, and
         (c) a binding element that specifically inter-
         acts with a selected target, wherein the
         costimulatory signaling region comprises
         the amino acid sequence encoded by SEQ
         ID NO:6.
 Dependent claims 3 and 9 limit the claimed “binding ele-
 ment” to “a single chain antibody,” i.e., an scFv. Claims 5
 and 11, which depend from claims 3 and 9, respectively,
 further specify that the claimed scFv binds to CD19.
     Kite’s YESCARTA® is a “therapy in which a patient’s T
 cells are engineered to express a [CAR] to target the anti-
 gen CD19, a protein expressed on the cell surface of B-cell
 lymphomas and leukemias, and redirect the T cells to kill
 cancer cells.” J.A. 58; J.A. 384; Kite Br. 17. It is a treat-
 ment that uses a three-part CAR containing an scFv that
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 JUNO THERAPEUTICS, INC.   v. KITE PHARMA, INC.                 5

 binds the CD19 antigen, a CD3-zeta chain portion, and a
 costimulatory signaling region. J.A. 58; see also Kite Br.
 11; J.A. 383–96 (Complaint).
      Juno sued Kite, alleging infringement of various claims
 of the ’190 patent through the use, sale, offer for sale, or
 importation of YESCARTA®. Kite filed counterclaims
 seeking declaratory judgments of noninfringement and in-
 validity of the ’190 patent. After a two-week jury trial, the
 jury reached a verdict in Juno’s favor, finding (1) Kite
 failed to prove the ’190 patent’s certificate of correction was
 invalid, (2) Kite failed to prove any of the asserted claims
 were invalid for lack of written description or enablement,
 (3) Juno proved Kite’s infringement was willful, and
 (4) Juno proved Kite owed damages amounting to a $585
 million upfront payment and a 27.6% running royalty.
      The parties then filed post-trial briefs. Kite moved for
 judgment as a matter of law (JMOL), arguing (a) the claims
 were not supported by a sufficient written description,
 (b) the claims were not enabled, (c) Juno’s certificate of cor-
 rection was invalid, (d) Kite acted in good faith such that it
 could not be found to be a willful infringer, and (e) Juno’s
 damages expert should have been excluded. J.A. 57, 60.
 Juno, for its part, moved for entry of judgment on the ver-
 dict, prejudgment interest, enhanced damages, and for the
 court to set an ongoing royalty rate. J.A. 38. The district
 court denied Kite’s motions for JMOL. J.A. 86. The district
 court granted-in-part Juno’s motion, updating the jury’s
 award to $778,343,501 to reflect updated YESCARTA® rev-
 enues through trial, awarding prejudgment interest, en-
 hancing damages by 50%, and awarding a 27.6% running
 royalty. J.A. 56.
     Kite appeals, arguing the district court erred in deny-
 ing JMOL on each of the above issues that Kite raised in
 its post-trial briefing.   We have jurisdiction under
 28 U.S.C. § 1295(a)(1). Because we determine that the rec-
 ord does not contain substantial evidence that the patent
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 6               JUNO THERAPEUTICS, INC.   v. KITE PHARMA, INC.

 contains written description support for the asserted
 claims, we hold the claims invalid and need not reach Kite’s
 alternative arguments.
                         DISCUSSION
     We review denial of a motion for JMOL under regional
 circuit law. See Trs. of Boston Univ. v. Everlight Elecs. Co.,
 896 F.3d 1357, 1361 (Fed. Cir. 2018). The Ninth Circuit
 reviews a denial of JMOL de novo, and reversal is appro-
 priate when “the evidence, construed in the light most fa-
 vorable to the nonmoving party, permits only one
 reasonable conclusion, and that conclusion is contrary to
 that of the jury.” White v. Ford Motor Co., 312 F.3d 998,
 1010 (9th Cir. 2002).
                               I
     A patent’s specification “shall contain a written de-
 scription of the invention.” 35 U.S.C. § 112 ¶ 1. 1 “[T]he
 hallmark of written description is disclosure.” Ariad
 Pharms., Inc. v. Eli Lilly & Co., 598 F.3d 1336, 1351 (Fed.
 Cir. 2010) (en banc). A specification adequately describes
 an invention when it “reasonably conveys to those skilled
 in the art that the inventor had possession of the claimed
 subject matter as of the filing date.” Id. at 1351. “A ‘mere
 wish or plan’ for obtaining the claimed invention is not ad-
 equate written description.” Centocor Ortho Biotech, Inc.
 v. Abbott Labs., 636 F.3d 1341, 1348 (Fed. Cir. 2011). What

     1    Paragraph 1 of 35 U.S.C. § 112 was replaced with
 newly designated § 112(a) by section 4(c) of the Leahy-
 Smith America Invents Act (“AIA”), Pub. L. No. 112-29,
 sec. 4, 125 Stat. 284, 296–97 (2011). Section 4(e) of the AIA
 makes those changes applicable “to any patent application
 that is filed on or after” September 16, 2012. Id. Because
 the applications resulting in the patent at issue in this case
 was filed before that date, we refer to the pre-AIA version
 of § 112.
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 is required to meet the written description requirement
 “varies with the nature and scope of the invention at issue,
 and with the scientific and technologic knowledge already
 in existence.” Capon v. Eshhar, 418 F.3d 1349, 1357 (Fed.
 Cir. 2005); see also Ariad, 598 F.3d at 1351.
      As we explained in Ariad, “[f]or generic claims, we have
 set forth a number of factors for evaluating the adequacy
 of the disclosure, including ‘the existing knowledge in the
 particular field, the extent and content of the prior art, the
 maturity of the science or technology, [and] the predictabil-
 ity of the aspect at issue.’” 598 F.3d at 1351 (citing Capon,
 418 F.3d at 1359). For genus claims using functional lan-
 guage, like the binding function of the scFvs claimed here,
 the written description “must demonstrate that the appli-
 cant 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 func-
 tionally-defined genus.” Ariad, 598 F.3d at 1349. “The
 written description requirement [ ] ensures that when a pa-
 tent claims a genus by its function or result, the specifica-
 tion recites sufficient materials to accomplish that
 function.” Id. at 1352. Generally, a genus can be suffi-
 ciently disclosed by “either a representative number of spe-
 cies 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. at 1350. “A written description of an
 invention involving a chemical genus, like a description of
 a chemical species, ‘requires a precise definition, such as by
 structure, formula, [or] chemical name,’ of the claimed sub-
 ject matter sufficient to distinguish it from other materi-
 als.” Regents of the Univ. of Cal. v. Eli Lilly & Co., 119 F.3d
 1559, 1568 (Fed. Cir. 1997) (quoting Fiers v. Revel, 984 F.2d
 1164, 1171 (Fed. Cir. 1993)).
     Whether a patent complies with the written descrip-
 tion requirement of § 112 ¶ 1 is a question of fact, and “we
 review a jury’s determinations of facts relating to
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 8               JUNO THERAPEUTICS, INC.   v. KITE PHARMA, INC.

 compliance with the written description requirement for
 substantial evidence.” Ariad, 598 F.3d at 1355 (quoting
 PIN/NIP, Inc. v. Platte Chem. Co., 304 F.3d 1235, 1243
 (Fed. Cir. 2002)).
                               II
     Kite argues that the asserted claims are invalid for fail-
 ing to satisfy the written description requirement because
 the ’190 patent discloses neither representative species nor
 common structural features of the claimed scFv genus to
 identify which scFvs would function as claimed. Kite ar-
 gues that the claims cover an enormous number (millions
 of billions) of scFv candidates, only a fraction of which sat-
 isfy the functional binding limitation for any given target,
 and that the written description does not meet the written
 description requirement for this functional binding limita-
 tion. It also argues that the scFv field is unpredictable
 since an scFv’s binding ability depends on a variety of fac-
 tors.
     Juno responds that scFvs were well-known (as was how
 to make them), that multiple scFvs for specific targets were
 well-known, that the ’190 patent describes two working
 scFv embodiments that are representative of all scFvs, and
 that scFvs had been incorporated in CARs well before the
 ’190 patent’s priority date. It also argues that scFvs are
 interchangeable and have common structural features.
     We agree with Kite that no reasonable jury could find
 the ’190 patent’s written description sufficiently demon-
 strates that the inventors possessed the full scope of the
 claimed invention. We hold that substantial evidence does
 not support the jury’s finding of adequate written descrip-
 tion for any of the asserted claims.
                               A
     The broadest asserted claims of the ’190 patent, claims
 3 and 9, recite that the scFv binding element “specifically
 interacts with a selected target.” As the ’190 patent
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 explains, “[t]he target . . . can be any target of clinical in-
 terest to which it would be desirable to induce a T cell re-
 sponse.” ’190 patent at 4:36–39 (emphasis added). In other
 words, claims 3 and 9 broadly cover, as part of the claimed
 nucleic acid polymer encoding for the three-part CAR, any
 scFv for binding any target. But the ’190 patent’s written
 description fails to provide a representative sample of spe-
 cies within, or defining characteristics for, that expansive
 genus.
                               1
     The ’190 patent’s written description contains scant de-
 tails about which scFvs can bind which target antigens.
 The ’190 patent discloses two example scFvs for binding
 two different targets: one derived from J591, which targets
 a PSMA antigen on prostate cancer cells, and another de-
 rived from SJ25C1, which targets CD19. J.A. 32922–23;
 J.A. 32967; J.A. 33945. The ’190 patent contains no details
 about these scFv species beyond the alphanumeric desig-
 nations J591 and SJ25C1 for a skilled artisan to determine
 how or whether they are representative of the entire
 claimed genus. Juno argues these two working embodi-
 ments are representative of all scFvs in the context of a
 CAR. The evidence does not support Juno’s argument. The
 claims are directed to scFvs that bind to selected targets.
 In claims 3 and 9 there is no limit as to the particular tar-
 get. To satisfy the written description requirement, the pa-
 tent needed to demonstrate to a skilled artisan that the
 inventors possessed and disclosed in their filing the partic-
 ular species of scFvs that would bind to a representative
 number of targets. Kite demonstrated by clear and con-
 vincing evidence that this patent does not satisfy the writ-
 ten description requirement for the claims at issue and this
 record does not contain substantial evidence upon which a
 jury could have concluded otherwise. The disclosure of one
 scFv that binds to CD19 and one scFv that binds to a PSMA
 antigen on prostate cancer cells in the manner provided in
 this patent does not provide information sufficient to
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 10              JUNO THERAPEUTICS, INC.   v. KITE PHARMA, INC.

 establish that a skilled artisan would understand how to
 identify the species of scFvs capable of binding to the lim-
 itless number of targets as the claims require.
     Juno primarily relies on the testimony of its immuno-
 logical expert, Dr. Brocker, but that testimony is far too
 general. Dr. Brocker testified that the two exemplary
 scFvs are representative “because [scFvs] all do the same
 thing. They bind to the antigen.” J.A. 33945. Nothing
 about that testimony explains which scFvs will bind to
 which target or cures the ’190 patent’s deficient disclosure
 on this score. 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 mere
 fact that scFvs in general bind does not demonstrate that
 the inventors were in possession of the claimed invention.
      This is not to say, however, that a patentee must in all
 circumstances disclose the nucleotide or amino acid se-
 quence of the claimed scFvs to satisfy the written descrip-
 tion requirement when such sequences are already known
 in the prior art. See Capon, 418 F.3d at 1360–61 (holding
 it was error for the Board of Patent Appeals and Interfer-
 ences to require “recitation in the specification of the nu-
 cleotide sequence of claimed DNA, when that sequence is
 already known in the field”). But the written description
 must lead a person of ordinary skill in the art to under-
 stand that the inventors possessed the entire scope of the
 claimed invention. Ariad, 598 F.3d at 1353–54 (“[T]he pur-
 pose of the written description requirement is to ensure
 that the scope of the right to exclude, as set forth in the
 claims, does not overreach the scope of the inventor’s con-
 tribution to the field of art as described in the patent spec-
 ification.”    (internal    quotation     marks     omitted)).
 Dr. Sadelain, one of the ’190 patent’s inventors, testified
 that, at the time he filed his patent application, he had
 used only the SJ25C1-derived scFv and J591-derived scFv.
 J.A. 32965–67. Yet the ’190 patent claims any scFv on its
 CAR that binds to any target, without disclosing details
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 JUNO THERAPEUTICS, INC.   v. KITE PHARMA, INC.               11

 about which scFvs bind to which target. It is not fatal that
 the amino acid sequences of these two scFvs were not dis-
 closed as long as the patent provided other means of iden-
 tifying which scFvs would bind to which targets, such as
 common structural characteristics or shared traits. But
 this patent provides nothing to indicate that the inventors
 possessed the full scope of the genus that they chose to
 claim. Thus, the ’190 patent’s disclosure does not demon-
 strate the inventors possessed the entire class of possible
 scFvs that bind to various selected targets.
      Relying upon witness testimony, Juno argues that be-
 cause scFvs, in general, were known, the two scFvs in the
 ’190 patent are representative. See, e.g., J.A. 32909
 (Dr. Sadelain testifying that scFvs were not new in the
 field, and that they “had been around since the [1980s]”);
 J.A. 33209 (Kite’s founder, Dr. Belldegrun, agreeing that
 “scientists knew about the scFvs that could be used with
 CARs going back to the 1980s”); J.A. 33932 (Juno’s expert,
 Dr. Brocker, testifying that scFvs “were in the field for
 more than a decade, nearly 15 years” at the time of
 Dr. Sadelain’s invention); J.A. 33939–40 (Dr. Brocker tes-
 tifying that people knew how to make scFvs and “several of
 them had been described”). To satisfy written description,
 however, the inventors needed to convey that they pos-
 sessed the claimed invention, which encompasses all scFvs,
 known and unknown, as part of the claimed CAR that bind
 to a selected target. Even accepting that scFvs were known
 and that they were known to bind, the specification pro-
 vides no means of distinguishing which scFvs will bind to
 which targets. See Eli Lilly, 119 F.3d at 1568 (“A written
 description of an invention involving a chemical genus, like
 a description of a chemical species, ‘requires a precise defi-
 nition, such as by structure, formula, [or] chemical name,’
 of the claimed subject matter sufficient to distinguish it
 from other materials.” (quoting Fiers, 984 F.2d at 1171)).
 Accordingly, testimony that scFvs were generally known in
 the field is insufficient to satisfy the written description
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 12              JUNO THERAPEUTICS, INC.   v. KITE PHARMA, INC.

 requirement for the ’190 patent’s claims requiring scFvs
 that bind to a selected target.
     Juno relies heavily on our decision in Capon, arguing
 that we already determined that “scFvs were well-known
 CAR components that did not need to be detailed in CAR
 patents’ specifications to satisfy Section 112.” Juno Br. 27.
 Our Capon decision neither made the determination Juno
 alleges nor determined that the inventors there satisfied
 the written description requirement. Instead, we vacated
 the Board’s decision for imposing too high a standard to
 satisfy the written description requirement, and remanded
 for the Board to consider the evidence and determine
 whether the specification adequately supported the claims
 at issue. Capon, 418 F.3d at 1358–61; see also id. at 1358
 (“The Board’s rule that the nucleotide sequences of the chi-
 meric genes must be fully presented, although the nucleo-
 tide sequences of the component DNA are known, is an
 inappropriate generalization.”). Also, more was known in
 the prior art in Capon than here, particularly when the in-
 ventors here used only two scFvs as of the ’190 patent’s pri-
 ority date out of the vast number of possibilities. See id. at
 1355, 1358; J.A. 32965–67. Capon does not support Juno’s
 arguments regarding its exceedingly broad functional
 claim limitations. 2

      2   We agree with Juno that a patent specification
 need not redescribe known prior art concepts. Juno Br. 28
 (citing Immunex Corp. v. Sandoz Inc., 964 F.3d 1049, 1064
 (Fed. Cir. 2020)). The problem with the ’190 patent is that,
 although there were some scFvs known to bind some tar-
 gets, the claims cover a vast number of possible scFvs and
 an undetermined number of targets about which much was
 not known in the prior art.
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                                2
      In addition to lacking representative species, the ’190
 patent does not disclose structural features common to the
 members of the genus to support that the inventors pos-
 sessed the claimed invention. See Ariad, 598 F.3d at 1350.
 Juno argues that the ’190 patent satisfies the written de-
 scription requirement because scFvs are interchangeable,
 with a similar, common structure.             It relies on
 Dr. Brocker’s testimony that scFvs have “known structural
 commonalities, similarities.” J.A. 33926. He explained
 that scFvs have the same general, common structure con-
 sisting of a variable region derived from the light chain of
 an antibody and a variable region derived from the heavy
 chain of an antibody, where these two portions are con-
 nected with a linker. J.A. 33936–38. These general asser-
 tions of structural commonalities, in the context of the
 technology in this case, are insufficient.
     It is undisputed that scFvs generally have a common
 structure, as described by Dr. Brocker. But, as Dr. Brocker
 acknowledged, an scFv with the same general common
 structure but with a different amino acid sequence would
 recognize a different antigen. J.A. 33938. Dr. Brocker also
 testified that all scFvs have a common structure, regard-
 less of whether they bind. J.A. 33959. The ’190 patent not
 only fails to disclose structural features common to scFvs
 capable of binding specific targets, it also fails to disclose a
 way to distinguish those scFvs capable of binding from
 scFvs incapable of binding those targets. The ’190 patent
 provides no amino acid sequences or other distinguishing
 characteristics of the scFvs that bind. Simply put, the ’190
 patent claims a “problem to be solved while claiming all so-
 lutions to it . . . cover[ing] any compound later actually in-
 vented and determined to fall within the claim’s functional
 boundaries,” Ariad, 598 F.3d at 1353, which fails to satisfy
 the written description requirement.
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 14              JUNO THERAPEUTICS, INC.   v. KITE PHARMA, INC.

     We have previously held similar claims invalid based
 on lack of written description. In Idenix, we held invalid
 claims that required nucleosides effective against hepatitis
 C virus, and 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).
 Without this explanation, “a [person of ordinary skill] is de-
 prived of any meaningful guidance into what compounds
 beyond the examples and formulas, if any, would provide
 the same result.” Id. Similarly, in AbbVie, we concluded
 that substantial evidence supported the jury’s verdict of in-
 adequate written description when the patents described
 one species of structurally similar antibodies derived from
 only one lead antibody but the asserted claims covered
 “every fully human IL-12 [targeted] antibody that would
 achieve a desired result” without an indication about an
 established correlation between the structure and the
 claimed function. AbbVie Deutschland GmbH v. Janssen
 Biotech, Inc., 759 F.3d 1285, 1301–02 (Fed. Cir. 2014). 3 As

      3   Juno also relies on Erfindergemeinschaft UroPep
 GbR v. Eli Lilly & Co., 276 F. Supp. 3d 629 (E.D. Tex.
 2017), aff’d, 739 F. App’x 643 (Fed. Cir. 2018). In that case,
 there were hundreds of known PDE5 inhibitors, the type of
 compound at issue, and the patent identified the com-
 pounds by chemical name and structural drawings. Id. at
 645–46. The compounds also shared a common physical
 structure to fit the active site of the PDE5 enzyme to inhibit
 its activity, and the evidence supported that a skilled arti-
 san “could make modifications to increase potency and se-
 lectivity.” Id. at 652–53. The ’190 patent, in contrast, does
 not disclose any amino acid sequences or structures to dis-
 tinguish scFvs that bind to selected targets from those that
 do not, and the modifications of the sequence can change
 the binding ability. Juno also does not dispute that very
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 JUNO THERAPEUTICS, INC.   v. KITE PHARMA, INC.               15

 in these two cases, the ’190 patent does not provide mean-
 ingful guidance about which scFv will bind which target.
     Claims 3 and 9 broadly claim all scFvs, as part of the
 claimed CAR, that bind to any target. But the written de-
 scription of the ’190 patent discloses only two scFv exam-
 ples and provides no details regarding the characteristics,
 sequences, or structures that would allow a person of ordi-
 nary skill in the art to determine which scFvs will bind to
 which target. That scFvs in general were well-known or
 have the same general structure does not cure that defi-
 ciency. Thus, substantial evidence does not support the
 jury’s finding that the ’190 patent conveys, to a skilled ar-
 tisan, that the inventors possessed the broad genus of
 scFvs as recited in claims 3 and 9.
                               B
     Claims 5 and 11, which are limited to scFvs that bind
 CD19 (a specific target), likewise find no written descrip-
 tion support in the ‘190 patent. And again, Juno’s general
 testimony about general scFv structure does not provide
 substantial evidence regarding the claims containing the
 functional limitation that covers all scFvs that bind to
 CD19.
     Kite argues that there were “four or five” CD19-specific
 scFvs “arguably known in the art” at the priority date of
 the ’190 patent. Kite Br. 35. Kite argues that the universe
 of possible sequences for scFvs is in the range of “millions
 of billions.” Id. at 26. Given the vast number of possible
 scFvs, the lack of detail in the ’190 patent regarding the
 scFv sequences, and the few scFvs known in the art to bind
 CD19, Kite argues substantial evidence does not support

 few CD19-specific scFvs were known as of the priority date.
 See § II.B below.
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 16              JUNO THERAPEUTICS, INC.   v. KITE PHARMA, INC.

 that the ’190 patent discloses species representative of the
 claimed genus.
     Juno does not dispute Kite’s characterizations regard-
 ing either the number of known CD19 scFvs at the priority
 date of the ’190 patent or the universe of possible scFvs.
 Instead, it cites Dr. Brocker’s general testimony that “there
 were several known” CD19 scFvs and publications “which
 have demonstrated that it’s possible to make these single-
 chain Fvs that can bind to CD19.” J.A. 33942. Juno also
 acknowledges that the ’190 patent discloses only one CD19-
 specific scFv (the SJ25C1-derived scFv), but argues that a
 second CD19-specific scFv, the one used in YESCARTA®,
 was known by 1997. Juno Br. 24.
     Substantial evidence does not support the jury’s find-
 ing that the ’190 patent disclosed sufficient information to
 show the inventors possessed the claimed genus of func-
 tional CD19-specific scFvs as part of their claimed CAR.
 The ’190 patent provides no details about any CD19-
 specific scFv, such as an exemplary amino acid sequence, a
 shape, or general characteristics that would allow this tar-
 get-specific scFv to bind. Instead, it provides only an al-
 phanumeric designation, SJ25C1, as the source for the
 CD19-specific scFv. Without more guidance, in a vast field
 of possible CD19-specific scFvs with so few of them known,
 no reasonable jury could find the inventors satisfied the
 written description requirement.
     Juno’s reliance on a combination of expert and inventor
 testimony does not provide the required support.
 Dr. Brocker’s testimony that “there were several [CD19
 scFvs] known” at the priority date and that it was “possible
 to make these single-chain Fvs that can bind CD19,”
 J.A. 33942, at most demonstrates a small number of CD19-
 specific scFvs were known and others were possible, albeit
 undiscovered. Indeed, Dr. Sadelain admitted that the
 SJ25C1-derived scFv was the only CD19-specific scFv he
 used at the time he filed his patent application. J.A. 32965.
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 And Juno’s reliance on only one more CD19-specific scFv,
 the one used in YESCARTA®, further demonstrates that
 the number of known CD19-specific scFvs at the time was
 small. Juno again relies on Dr. Brocker, who testified that
 he was not “aware of any functional CD19 scFv that has
 not been shown to work with Dr. Sadelain’s CAR back-
 bone.” J.A. 33943–44 (emphasis added). But that testi-
 mony presupposes an scFv already known to be functional;
 one that was known to bind to CD19. Such circular reason-
 ing does not support that the inventors possessed the full
 scope of possible CD19-specific scFvs, particularly when
 the genus of possibilities is expansive with only four or five
 CD19 scFv species known at the time. Finally, Juno relies
 on Dr. Sadelain’s testimony that, since he filed his patent
 application, he has “placed multiple scFvs” on the CAR
 backbone, “probably up to 30 [CD19-specific scFvs] by
 now.” J.A. 32923. 4 But we assess whether the written de-
 scription requirement is satisfied as of the filing date of the
 patent application. Ariad, 598 F.3d at 1351. Dr. Sadelain’s
 testimony about post-priority date developments, there-
 fore, is irrelevant to the inquiry before us. See id. at 1355
 (post-priority date evidence “legally irrelevant to the ques-
 tion of whether” the disclosure conveyed possession at the
 time of filing).
     Juno’s further arguments that it would not matter to a
 person of ordinary skill (1) that scFvs may be highly di-
 verse in the abstract, (2) that “millions of billions” of scFvs
 would need to be made and tested to ascertain their bind-
 ing properties, or (3) that a skilled artisan could not predict

     4   Fifteen years after the ’190 patent’s priority date,
 individuals from Juno published an article, J.A. 37426–34,
 in which they discussed having screened over a billion hu-
 man scFv sequences to arrive at only 60 that “displayed el-
 evated binding to CD19-expressing cells,” J.A. 37427–28.
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 18              JUNO THERAPEUTICS, INC.   v. KITE PHARMA, INC.

 before testing whether an scFv would bind, Juno Br. 28–
 29, are contrary to our precedent. In Ariad, we explained
 that “the level of detail required to satisfy the written de-
 scription requirement varies depending on the nature and
 scope of the claims and on the complexity and predictabil-
 ity of the relevant technology.” 598 F.3d at 1351. Some
 factors to consider when evaluating the adequacy of the
 disclosure include “the existing knowledge in the particu-
 lar field, the extent and content of the prior art, the ma-
 turity of the science or technology, [and] the predictability
 of the aspect at issue.” Id. (alteration in original) (citing
 Capon, 418 F.3d at 1359). Contrary to Juno’s argument,
 the diversity of the functional scFv genus, the unpredicta-
 bility of an scFv’s binding ability, and that the prior art
 had, at most, five CD19-specific scFvs as of the priority
 date are all relevant to the written description inquiry.
      We likewise reject Juno’s argument that our decision
 in Ariad is “irrelevant” because the claims at issue here do
 not involve method claims reciting a “newly-identified cel-
 lular function or mechanism of action.” Juno Br. 25. Juno
 relies on its expert’s testimony that Dr. Sadelain invented
 the backbone, not scFvs. J.A. 33932; see also J.A. 33934
 (Dr. Brocker testifying that scFvs were “not part of this in-
 vention. The real invention was the backbone.”). But the
 ’190 patent’s claims are not limited to just the claimed
 backbone; they also include the functional scFv for binding
 the target. As we explained in Boston Scientific Corp. v.
 Johnson & Johnson, “[t]he test for written description is
 the same whether the claim is to a novel compound or a
 novel combination of known elements. The test is the same
 whether the claim element is essential or auxiliary to the
 invention.” 647 F.3d 1353, 1365 (Fed. Cir. 2011). The ’190
 patent inventors, therefore, needed to provide a sufficient
 disclosure that “reasonably conveys to those skilled in the
 art that the inventor[s] had possession of the claimed sub-
 ject matter as of the filing date,” Ariad, 598 F.3d at 1351,
 including for the claimed functional binding element.
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     While it is true that scFvs in general were known, and
 even known to bind, the record demonstrates that, for even
 the narrowest claims at issue, the realm of possible CD19-
 specific scFvs was vast and the number of known CD19-
 specific scFvs was small (five at most). The ’190 patent,
 however, provides no details about which scFvs bind to
 CD19 in a way that distinguishes them from scFvs that do
 not bind to CD19. Without this guidance, under our con-
 trolling Ariad decision, no reasonable jury could find the
 ’190 patent satisfies the written description requirement.
                        CONCLUSION
     Substantial evidence does not support the jury’s verdict
 in Juno’s favor on the issue of written description. For the
 claimed functional scFv genus, the ’190 patent does not dis-
 close representative species or common structural features
 to allow a person of ordinary skill in the art to distinguish
 between scFvs that achieve the claimed function and those
 that do not. Accordingly, we reverse.
                        REVERSED
                             COSTS
 Costs to Kite.