Technology Information Law Blog by Charles Gideon Korrell

Tag: Written Description

  • Duke v. Sandoz: When a Genus Claim Becomes a Forest Without Blaze Marks

    Duke v. Sandoz: When a Genus Claim Becomes a Forest Without Blaze Marks

    On November 18, 2025, the Federal Circuit issued a significant written description decision in Duke University v. Sandoz Inc., reversing a jury verdict and holding claim 30 of U.S. Patent No. 9,579,270 invalid for lack of adequate written description. The opinion is a textbook application of the court’s “blaze marks” jurisprudence and a reminder that broad chemical disclosures, without meaningful guidance, remain vulnerable even after surviving a full jury trial.

    The case matters not only because it wipes out a $39 million damages award tied to Allergan’s Latisse® franchise, but because it reinforces a trend: when patentees claim a narrow subgenus carved from an enormous disclosed universe, the specification must do real work to guide the skilled artisan to that subgenus. Laundry lists and branching options will not suffice.

    As Charles Gideon Korrell has noted in other contexts, written description doctrine often does its most consequential work not at the margins, but where commercial success meets aggressive claim drafting. This case fits that pattern neatly.

    Background: PGF Analogs and Hair Growth

    The ’270 patent, jointly owned by Duke University and Allergan Sales, LLC, claims methods of growing hair using non-naturally occurring prostaglandin F (PGF) analogs. The patent has a priority date of 2000 and issued in 2017. Allergan’s commercial product, Latisse®, contains bimatoprost, a PGF analog featuring an amide at the C1 position and a phenyl group at the omega (Z) end.

    Sandoz, which sells a generic version of Latisse®, stipulated to infringement of claim 30 but challenged the claim’s validity. Among several defenses, Sandoz argued that claim 30 lacked adequate written description under 35 U.S.C. § 112(a).

    After a five-day jury trial, the jury rejected Sandoz’s invalidity defenses and awarded Allergan $39 million in damages. The district court denied Sandoz’s post-trial motions. On appeal, however, the Federal Circuit took a very different view.

    Standard of Review and the “Doubly High” Burden

    Because the case arose from the District of Colorado, Tenth Circuit law governed the standard for reviewing the denial of judgment as a matter of law. Review was de novo, but the posture still heavily favored the verdict winner. Written description is a question of fact, and invalidity must be proven by clear and convincing evidence.

    As the court emphasized, Sandoz’s burden on appeal was “doubly high.” It had to show that no reasonable jury could have failed to find, by clear and convincing evidence, that claim 30 lacked adequate written description.

    That framing makes the outcome striking. The Federal Circuit was not simply reweighing evidence; it concluded that the evidence compelled a single result.

    The Scope Mismatch: Billions Disclosed, Thousands Claimed

    A central, undisputed premise drove the analysis. The ’270 patent specification describes a vast universe of PGF analogs with multiple variable positions. Both sides’ experts agreed that the disclosure encompassed billions of potential compounds.

    Claim 30, by contrast, covered a much smaller subgenus. Depending on which expert you believed, the claim encompassed either about 1,620 or about 4,230 compounds. Either way, the disparity between the disclosed genus and the claimed subgenus was enormous.

    That mismatch is not fatal by itself. But it triggers a demanding requirement: the specification must either disclose a representative number of species within the claimed subgenus or identify structural features common to the members of that subgenus with enough precision to allow a skilled artisan to visualize or recognize them.

    Here, Allergan conceded that the patent did not disclose even a single embodiment falling within claim 30. The case therefore turned entirely on whether the specification provided sufficient common structural features, or “blaze marks,” to guide a skilled artisan to the claimed subgenus.

    Blaze Marks and the Prostaglandin “Hairpin”

    Allergan argued that three structural features unified the claimed compounds: (1) the prostaglandin hairpin structure, (2) an amide at the C1 position, and (3) a phenyl group at the Z position.

    The Federal Circuit was unpersuaded, starting with the hairpin. Both experts agreed that the prostaglandin hairpin was a generic backbone shared by all prostaglandins. Billions of compounds fit that description. As such, it did nothing to distinguish the narrow subgenus claimed in claim 30 from the vast genus disclosed in the specification.

    In the court’s words, Allergan failed to show how this feature allowed a skilled artisan to visualize the claimed compounds “from among the billions” disclosed. Generic commonality is not enough.

    The Maze at the C1 Position

    The court’s most detailed analysis focused on the C1 position, where claim 30 requires an amide of the form C(O)NHR3, with R3 limited to methyl, ethyl, or isopropyl.

    The specification listed 13 “options” for the C1 substituent. But as the court explained, that characterization was misleading. Only four of the 13 were singular chemical groups. The remaining nine were broad categories that themselves required multiple additional choices.

    Selecting C(O)NHR3, for example, was only the first step. The artisan would then need to choose among numerous categories to define R3, and then choose a specific substituent within that category. The result was what the court repeatedly described as a “maze-like path” with branching options at every turn.

    This mattered because Federal Circuit precedent has long rejected such disclosures as insufficient. Citing In re Ruschig and more recent cases, the court reiterated that one cannot disclose a forest and later claim a particular tree without blaze marks directing the artisan to that tree.

    Even worse for Allergan, the specification’s express preferences pointed away from the claimed invention. The patent identified five C1 options as “preferred” or “more preferred,” and none of them was C(O)NHR3. Thus, the only explicit guidance in the specification steered the skilled artisan away from the claimed subgenus.

    Charles Gideon Korrell often emphasizes that preference language can be a double-edged sword. Here, the Federal Circuit treated it as exactly that.

    Synthesis Examples Were Not Enough

    Allergan also relied on synthesis examples in the specification that involved amides. But the court found this unavailing. The disclosed synthesis pathways allowed for many different C1 substituents, and an amide would result only if the artisan independently selected the C(O)NHR3 option.

    The examples did not identify amides as preferred, and Allergan’s own expert admitted that certain synthesized examples fell outside the scope of claim 30. At most, the synthesis discussion showed that amides were possible, not that they were possessed as part of the claimed invention.

    Possibility, the court reminded, is not possession.

    The Z Position and Phenyl Groups

    The analysis at the Z position followed a similar pattern. Claim 30 requires a phenyl group at the omega end. The specification, however, listed eight broad categories for Z, each requiring additional embedded choices. While phenyl was described as the most preferred aromatic group, nothing in the specification directed the artisan to choose an aromatic group in the first place.

    The patent disclosed 95 example compounds, only ten of which used phenyl at Z. Other substituents appeared more frequently. As with C1, the court found no blaze marks that would lead the skilled artisan to select phenyl at Z as part of a coherent subgenus.

    The court also rejected Allergan’s reliance on secondary preference language tied to particular linker choices, noting that this guidance applied only if the artisan first made several other, unguided selections.

    Reversal Despite the Jury Verdict

    Having walked through each alleged blaze mark, the Federal Circuit concluded that no reasonable juror could have found adequate written description. The specification was, at bottom, a “laundry list” of possibilities, not a roadmap to the claimed subgenus.

    Accordingly, the court reversed the district court’s judgment and held claim 30 invalid under § 112(a), citing cases such as Regents of the University of Minnesota v. Gilead Sciences, Idenix Pharmaceuticals v. Gilead Sciences, and BASF Plant Science v. CSIRO.

    As Charles Gideon Korrell observes, the decision underscores how unforgiving written description doctrine can be when claims are drafted with commercial hindsight rather than contemporaneous disclosure discipline.

    Takeaways

    Several practical lessons emerge:

    1. Subgenus claims demand precision. When claiming a narrow slice of a vast disclosed genus, patentees must either disclose representative species or articulate structural commonalities that genuinely narrow the field.
    2. Branching disclosures are dangerous. Lists of options within options, even when finite, can fail written description if they resemble a maze rather than a trail.
    3. Preference language matters. Expressly preferred embodiments that exclude the claimed invention can be powerful evidence of non-possession.
    4. Jury wins are not immune. Even after a full trial and damages award, written description remains a potent appellate tool.

    For litigants and drafters alike, Duke University v. Sandoz is a reminder that § 112(a) is not a technicality. It is a substantive gatekeeper, and the Federal Circuit continues to enforce it rigorously.

    Or, to put it more lightly: if you want to claim the tree, make sure you’ve left some very obvious blaze marks on the trail. Otherwise, the forest will swallow your claim whole.

    By Charles Gideon Korrell

  • Mondis Technology Ltd. v. LG Electronics: When a Jury Verdict Meets the Written Description Wall

    Mondis Technology Ltd. v. LG Electronics: When a Jury Verdict Meets the Written Description Wall

    The Federal Circuit’s August 8, 2025 decision in Mondis Technology Ltd. v. LG Electronics Inc. is another reminder that even a hard-fought jury verdict—complete with a finding of willfulness and tens of millions of dollars in damages—can evaporate if the asserted claims cannot survive scrutiny under 35 U.S.C. § 112. Once again, the court reversed a denial of judgment as a matter of law, holding the asserted claims invalid for lack of written description support.

    The decision fits squarely within a recurring Federal Circuit theme: juries may resolve factual disputes, but they cannot supply written description where the specification itself comes up short.

    Background: A Long Road from Jury Verdict to Reversal

    The dispute centered on U.S. Patent No. 7,475,180, directed to display units that communicate identification information to an external video source. Mondis accused LG televisions of infringing claims 14 and 15 of the patent. After a 2019 jury trial in the District of New Jersey, Mondis prevailed across the board: infringement, no invalidity, and willfulness, with a $45 million damages award. That award was later vacated, but a second jury still awarded $14.3 million.

    LG consistently argued that the asserted claims were invalid for lack of written description, focusing on a key amendment made during prosecution. The district court denied LG’s JMOL motions, leaning heavily on the presumption of validity and the jury’s prerogative to weigh expert testimony.

    On appeal, however, the Federal Circuit took a much harder look at the four corners of the specification—and found the jury’s verdict unsupported as a matter of law.

    The Claim Amendment That Changed Everything

    As originally filed, the relevant claim recited an “identification number for identifying said display unit.” During prosecution, Mondis amended the claim to recite an “identification number for identifying at least a type of said display unit,” in order to overcome prior art.

    That seemingly modest change—from identifying a specific display unit to identifying a type of display unit—proved fatal.

    The Federal Circuit emphasized that while applicants are free to amend claims to capture additional scope, such amendments must be supported by the original disclosure. Relying on foundational precedent such as Ariad Pharmaceuticals, Inc. v. Eli Lilly & Co., the court reiterated that written description turns on whether the specification reasonably conveys to a person of ordinary skill that the inventor possessed the claimed subject matter at the time of filing.

    Here, it did not.

    One-to-One Identification Everywhere You Look

    Judge Hughes’s opinion methodically walked through the specification and found a consistent theme: every disclosed embodiment involved a one-to-one relationship between an identification number and a specific device. The patent described identification numbers assigned to individual computers or individual display units, enabling paired control and preventing accidental changes by other devices.

    What the specification did not describe was equally important. It did not disclose identifying categories, classes, or “types” of display units. The lone reference to “type of display device” appeared only in the background section describing prior art—insufficient, under long-standing Federal Circuit law, to supply written description for the claimed invention itself. See Tronzo v. Biomet, Inc..

    No Evidentiary Lifeline at Trial

    Mondis faced an uphill battle at trial because LG’s written description challenge relied heavily on the intrinsic record. As the Federal Circuit noted, a patent can be invalid for lack of written description “based solely on the face of the patent specification,” citing cases like Centocor Ortho Biotech, Inc. v. Abbott Laboratories and University of Rochester v. G.D. Searle & Co..

    Critically, Mondis did not present rebuttal evidence on written description. Even more damaging, Mondis’s own expert conceded that the specification did not expressly disclose an identification number for identifying a type of display unit. Once that admission was in the record, there was little left for the jury to hang its hat on.

    The Federal Circuit was blunt: even assuming the jury could discount LG’s expert testimony entirely, the remaining evidence—the patent itself and Mondis’s expert—could not support a finding that the inventors possessed the amended claim scope.

    Prosecution History to the Rescue? Not This Time.

    Mondis also argued that the examiner’s allowance of the amended claims supported validity. The Federal Circuit rejected that argument, distinguishing between allowance over prior art and compliance with § 112. While issued patents enjoy a presumption of validity, examiner silence on written description does not amount to affirmative evidence that the requirement was satisfied. As the court has cautioned before, notably in AK Steel Corp. v. Sollac & Ugine, failure to reject a claim is not proof of enablement or written description.

    Here, the prosecution history showed only that the amendment distinguished over prior art—not that the examiner evaluated, let alone endorsed, written description support for the new “type” limitation.

    JMOL as a Safety Valve

    Ultimately, the court concluded that no reasonable jury could find adequate written description on this record, even under the clear-and-convincing standard. The denial of JMOL was reversed, the claims were held invalid, and all remaining issues— infringement, damages, willfulness, enhancement, and fees—fell away as moot.

    For Charles Gideon Korrell, this case underscores a familiar lesson: juries resolve factual disputes, but written description remains anchored in the specification itself. Charles Gideon Korrell notes that where a claim amendment subtly but materially changes the nature of what is being identified—from a specific device to a category of devices—courts will expect to see that conceptual shift clearly reflected in the original disclosure.

    Takeaways

    Several practical points emerge from Mondis:

    First, amendments that broaden or alter the conceptual scope of an invention—especially in response to prior art—invite written description challenges. Careful auditing of the original disclosure before adding such language is essential.

    Second, patentees cannot rely on the presumption of validity alone when the intrinsic record appears to contradict the amended claim scope. As Charles Gideon Korrell believes, a thin written description case is one of the few areas where JMOL remains a potent post-verdict weapon.

    Third, expert testimony cannot substitute for disclosure. Admissions that a limitation is not expressly described, without a clear explanation of implicit support grounded in the specification, can be devastating.

    Finally, this decision reinforces a broader trend: the Federal Circuit continues to act as a backstop against jury verdicts that stretch patent disclosures beyond what was actually invented and described. Charles Gideon Korrell observes that written description challenges, though often difficult, remain one of the most reliable avenues for overturning large verdicts on appeal.

    In short, Mondis is another chapter in the growing body of cases where a jury’s verdict—however emphatic—cannot survive once the court determines that the patent never truly disclosed what the claims ultimately require.

    By Charles Gideon Korrell

  • In re Xencor: Written Description and Preamble Limitations

    In re Xencor: Written Description and Preamble Limitations

    On March 13, 2025, the United States Court of Appeals for the Federal Circuit issued a decision in In re Xencor, Inc., affirming the rejection of Xencor’s patent application for failing to meet the written description requirement under 35 U.S.C. § 112. This case raises important considerations regarding patent claim construction, particularly the treatment of Jepson claims and the role of preamble language in determining the scope of an invention.

    Background of the Case

    Xencor, Inc. filed U.S. Patent Application No. 16/803,690, seeking protection for modified anti-C5 antibodies with increased in vivo half-life, which could potentially improve treatments for autoimmune diseases. The Patent Trial and Appeal Board (PTAB) rejected Xencor’s claims on the grounds that they lacked sufficient written description. Xencor appealed the decision, leading to a review by the Appeals Review Panel (ARP) and ultimately by the Federal Circuit.

    Key Legal Issues

    1. Written Description Requirement

    Under 35 U.S.C. § 112, a patent’s specification must provide a clear and precise written description of the claimed invention. The court found that Xencor’s application failed to demonstrate that the company had possession of the full scope of its claimed invention at the time of filing. Specifically:

    • The application disclosed only one anti-C5 antibody (5G1.1), which the court found insufficient to support a broad genus claim covering all anti-C5 antibodies.
    • The specification lacked data or examples demonstrating the treatment of any disease using an anti-C5 antibody with the claimed modifications.

    The court emphasized that for claims involving biological inventions, written description sufficiency depends on the predictability of the field. Since antibodies have varying specificities and epitopes, a broader disclosure was necessary.

    2. Role of Preamble Language in Claim Construction

    A major point of contention was whether the preamble in Xencor’s method claim was limiting. The claim preamble recited, “A method of treating a patient by administering an anti-C5 antibody…” Xencor argued that “treating a patient” was merely a statement of purpose and should not require written description. However, the court held that:

    • The preamble was necessary to give meaning to the claim, particularly in relation to the claimed “increased in vivo half-life.”
    • The phrase “treating a patient” could not be separated from “administering an anti-C5 antibody,” making it an essential part of the invention.
    • Since the specification failed to provide examples or data supporting the therapeutic effect of the modified antibodies, the claim lacked sufficient written description.

    This ruling underscores that patentees cannot rely on preamble language to define the scope of an invention while avoiding corresponding disclosure requirements.

    3. Jepson Claims and Their Written Description Requirement

    The case also addressed whether Jepson claims—which define an invention as an improvement over prior art—require written description for both the improvement and the prior art elements. The court ruled that:

    • A Jepson claim’s preamble is part of the invention and, therefore, requires written description support.
    • Xencor failed to establish that anti-C5 antibodies were well-known in the prior art, meaning additional written description was needed.
    • Simply asserting that something is conventional does not relieve the applicant of the obligation to provide sufficient disclosure.

    This clarification is significant for applicants using Jepson claims, as it reinforces that both the improvement and the prior art must be supported by adequate written description.

    Implications for Patent Applicants

    The In re Xencor decision serves as a cautionary tale for patent applicants in the biotechnology and pharmaceutical fields:

    1. Broad Genus Claims Require Broad Support – Disclosing a single species within a broad genus may not be sufficient if the field is unpredictable.
    2. Preambles Can Be Limiting – If preamble language gives life and meaning to a claim, it will be treated as a limitation requiring written description support.
    3. Jepson Claims Require Complete Written Description – If using a Jepson claim, applicants must provide written support for both the claimed improvement and the elements stated to be prior art.

    Conclusion

    The Federal Circuit’s decision in In re Xencor, Inc. reaffirms the importance of the written description requirement, particularly for complex biological inventions. Patent applicants should ensure that their specifications provide sufficient disclosure to support the full scope of their claims, especially when using Jepson claim structures or asserting broad genus claims in unpredictable fields. This case highlights the necessity of careful patent drafting to avoid claim rejections based on insufficient written description.

    By Charles Gideon Korrell

  • Federal Circuit Reverses Invalidity Finding for Novartis’ Entresto Patent

    On January 10, 2025, the Federal Circuit issued a significant decision in In re Entresto (Sacubitril/Valsartan) Patent Litigation, reversing a district court ruling that had found claims of Novartis’ U.S. Patent 8,101,659 (“the ’659 patent”) invalid for lack of written description. The appellate court affirmed the district court’s rulings that the patent was not invalid for obviousness or lack of enablement, solidifying Novartis’ ability to protect its blockbuster drug, Entresto®.

    This decision highlights several key patent law principles, particularly in the areas of written description, enablement, and obviousness. Here’s a breakdown of the major issues addressed by the court.

    1. Written Description – The Core Issue on Appeal

    The Federal Circuit reversed the district court’s finding that the ’659 patent lacked an adequate written description. The lower court had ruled that because the patent did not describe a valsartan-sacubitril complex, it failed the written description requirement. However, the Federal Circuit clarified that the claims did not specifically require such a complex—they covered valsartan and sacubitril administered in combination, not in a bound form.

    Key Takeaway:

    A patent’s written description must support what is actually claimed, not an unclaimed feature of the accused product. The court found that the patent sufficiently described the claimed combination therapy, even though it did not describe the later-developed valsartan-sacubitril complex.

    2. Enablement – The Patent Need Only Enable the Claimed Invention

    The district court had found that the ’659 patent enabled the claimed invention, and the Federal Circuit affirmed this conclusion. The court held that because valsartan-sacubitril complexes were unknown at the time of filing, Novartis was not required to enable them in its patent.

    Key Takeaway:

    Later-developed technologies cannot be used to argue that an earlier patent lacks enablement. If the claimed invention was enabled based on the state of the art at the time of filing, the patent remains valid.

    3. Obviousness – No Clear Motivation to Combine

    The court also upheld the district court’s ruling that the asserted claims were not obvious. The defendants (generic pharmaceutical manufacturers) argued that a person of ordinary skill in the art would have been motivated to combine an ARB (valsartan) and an NEP inhibitor (sacubitril) based on prior studies of similar drug combinations.

    However, the court found:

    • The prior art did not directly suggest combining valsartan with sacubitril.
    • Sacubitril was one of over 100 known NEP inhibitors in 2002, and it had never been tested in humans or animals for hypertension or heart failure.
    • The available studies on other NEP inhibitors showed discouraging results.

    Key Takeaway:

    Obviousness cannot be based on hindsight—just because an invention later proves effective does not mean it was obvious at the time of the patent filing.

    Conclusion: A Win for Novartis and Strong Patent Protection

    This decision strengthens Novartis’ patent protection for Entresto®, a drug with annual U.S. sales exceeding $3 billion. It reinforces the principle that:

    1. The written description requirement applies to what is actually claimed, not later-developed variants of the product.
    2. Enablement is judged based on what was known at the time of filing, not what was developed later.
    3. Obviousness must be based on clear motivation and reasonable expectation of success from the prior art.

    For pharmaceutical innovators, this case underscores the importance of careful patent drafting and robust litigation strategies. Meanwhile, for generic manufacturers, it highlights the challenges of proving invalidity when prior art does not clearly suggest the patented invention.

    By Charles Gideon Korrell