In 2025, the Patent Trial and Appeal Board (PTAB) addressed more than 20 post-grant reviews (PGRs) and over 100 ex parte appeals involving issues under 35 U.S.C. § 112 in the life sciences field.[1] This article presents a summary of representative cases.
1. BeOne Medicines USA, Inc. v. Pharmacyclics LLC, PGR2024-00009
In April 2025, the Board issued a final written decision in BeOne Medicines USA, Inc. v. Pharmacyclics LLC, finding that all challenged claims of U.S. Patent No. 11,672,803 (the ’803 patent) were unpatentable due to lack of written description. The challenged claims recited a method for treating chronic lymphocytic leukemia (CLL) or small lymphocytic lymphoma (SLL) in an individual comprising administering a therapeutically effective amount of an irreversible inhibitor of Bruton’s tyrosine kinase (BTK). See PGR2024-00009, Paper 51, at 6-8. In particular, the BTK inhibitors of the claimed methods required certain structural features (e.g., a hydrophobic moiety, piperidine linker, and a generic Z′-structure consisting of a 5:6 heterocyclic ring) and functional features (e.g., administering a “therapeutically effective amount” that results in lymphocytosis). Id. at 29-30.
The Board concluded that “the claims encompass a very large number of possible species in light of the various optional substitutions of the Z′-structure.” Id. at 30. And during trial, Pharmacyclics conceded that the specification did not disclose a representative number of species of BTK inhibitors and argued that “this is a common structural features case.” Id. The Board, therefore, found that while the ’803 patent claimed a broad genus of BTK inhibitors defined by both structural and functional features, the specification did not adequately describe common structural features of the genus. Id. According to the Board, even with the claimed structural limitations, the scope of the claims could encompass a “very large” number of species, and the specification had insufficient blaze marks to guide a person of ordinary skill in the art (POSITA) from the disclosed generic structures to the full scope of the Z′-structures that could satisfy the functional limitations of the claims. Id. at 30-31, 35.
In reaching its conclusions, the Board also determined that the facts were analogous to those in Idenix Pharmaceuticals LLC v. Gilead Sciences Inc., 941 F.3d 1149 (Fed. Cir. 2019). According to the Board, the ’803 patent specification “discloses thousands of potential Z′-structures, but does not explain what makes them effective, or why.” Paper 51, at 35-36 (quoting Idenix at 1164). The Board also further compared the ’803 patent to the patent at issue in Idenix, where the accused product arose after the filing date of the patent at issue, because the Z’-structure of Pharmacyclics’ later-arising BTK inhibitor, zanubrutinib, was “conspicuously absent” from the ’803 patent specification. Id. The evidence also showed that “compounds that satisfy the Structural Limitations will not necessarily satisfy the Functional Limitations of the claims.” Id. at 43.
2. Charles River Laboratories, Inc. v. Seikagaku Corporation, PGR2025-00023
In September 2025, the Board instituted a PGR filed by Charles River Laboratories (CRL) against Seikagaku’s U.S. Patent No. 11,959,109 (the ‘109 patent). The ’109 patent is directed to “recombinant factor C and method for producing the same, and method for measuring endotoxin,” and the challenged claims recite “a method for producing an endotoxin assay agent comprising a horseshoe crab Factor C, Factor B, and Pro-clotting enzyme.” PGR2025-00023, Paper 14, at 7. CRL’s petition argued that the challenged claims were not entitled to their priority date due to lack of written description and enablement support in the patent’s priority applications. With a severed priority claim, CRL argued that the challenged claims were unpatentable as anticipated by an intervening prior art reference. CRL’s petition also raised grounds that the challenged claims themselves were unpatentable for lacking written description and enablement in the ’109 patent specification.
In its institution decision, the Board concluded that CRL’s petition only challenged § 112 support of the ’109 patent claims in the ’109 patent specification as of the 2013 claimed priority date, and did not assess written description or enablement as of the 2023 filing date of the application that led to the ’109 patent. Id. at 11-14. Relying on Ariad, the Board noted that “the person of ordinary skill in the art [in 2013] is not the same as in 2023.” Id. at 12 (citing Ariad at 1351). The Board similarly concluded that the petition “focuses on whether the [priority] application would have enabled a 2013 POSITA to practice the invention,” rather than a 2023 skilled artisan. Id. at 14. The Board accordingly concluded that the petition did not meet the threshold for institution based on the § 112 patentability challenges. Id. at 12-14.
The Board, however, did find that the petition’s priority challenge had merit, and that the intervening art reference may anticipate the challenged claims. The Board found that the challenged claims lacked written description and enablement as of 2013 because claim 1 of the ’109 patent included proteins from Limulus polyphemus, but the gene and sequence information for the Factor C, B, and Pro-clotting enzymes from L. polyphemus were not disclosed as of the claimed 2013 priority date. Id. at 24. Despite concerns of evidentiary admissibility, even a declaration that recited there was “no reason to believe that L. polyphemus Factor C would be difficult to express” was overcome by the fact that Seikagaku’s previous efforts to obtain recombinant cascade proteins from L. polyphemus had failed. Id. at 27-28. Accordingly, the Board determined that Seikagaku failed to meet its burden of production, thus it is preliminarily more likely than not that the ’629 publication is prior art over the challenged claims. This PGR is currently awaiting a final written decision, currently due in September 2026.
3. Ex parte Skiöldebrand, Appeal No. 2025-000232
In Ex parte Skiöldebrand, the Board affirmed the examiner’s written description rejections of the pending claims of U.S. Appl. No. 16/309,708 (the ’708 application). The ’708 application was directed to “compeptide and antibodies thereto for diagnosing osteoarthritis.” Pending claim 17 of the ’708 application, the only claim on appeal, recited a method of diagnosing early osteoarthritis in a horse comprising contacting an antibody that specifically binds to a nine amino acid-long N-terminal peptide of the horse protein COMP comprising the sequence SGPTH. See ’708 application File Wrapper, PTAB Decision, issued July 30, 2025, at 2.
The Board agreed with the examiner’s finding that the method “requires the use of an antibody defined solely by the antigen it binds.” Id. at 3. The Board found that the specification thus described a functional genus of antibodies useful in the claimed method “including polyclonal, monoclonal, Fab, Fab, F(ab’)2, Fv, and single-chain antibodies, encompassing a variety of different isotypes and specific functional characteristics … that may be produced … using an antigen that is a COMP peptide fragment of at least nine amino acids in length.” Id. at 5. Because of that, the Board found that even though the appellant’s claims were to a method and not to the antibody itself or a genus of antibodies, the ’708 application still needed to provide an adequate written description of the genus of antibodies to be used in the claimed method. Id. at 6-7.
Relying on Ariad v. Eli Lilly, the Board stated that the ’708 application needed to demonstrate possession of species sufficient to support the functionally defined genus. Id. at 5 (citing Ariad Pharm., Inc. v. Eli Lilly & Co., 598 F.3d 1336, 1349 (Fed. Cir. 2010) (en banc)). And the Board found that the ’708 application failed to do so because the application only identified the structure of the antigen and not sufficient species of antibodies encompassed by the claimed genus. The Board thus emphasized that an applicant must describe the invention itself to meet the written description requirement, and an applicant cannot simply claim a genus of antibodies by describing the antigen to which it binds. Id. at 6-7.
4. Ex parte Krause, Appeal No. 2025-000513
In Ex parte Krause, the Board affirmed the examiner’s written description rejection of the pending claims of U.S. Appl. No. 15/639,765 (the ’765 application). The claims of the ’765 application were directed to methods of cell-based therapy that comprised using pluripotent stem cells (PSCs) comprising a suicide gene under control of a cell-cycle dependent promoter. See ’765 application File Wrapper, PTAB Decision, issued Oct. 27, 2025, at 2. The examiner initially rejected the claims as lacking written description because, according to the examiner, the specification “discloses a limited number of exemplary genes which may be used as a ‘cell cycle dependent promoter’ and that the limited number was not representative of the genus.” Id. at 6.
The Board relied on Ariad and focused its analysis on whether the ’765 application’s specification provided disclosure of a sufficient number of species to support the claimed genus. Id. at 8. The Board found that, while the appellant argued that the 70 genes disclosed in the specification constituted a sufficient number of species to fulfill the written description requirement, those 70 genes were not representative of the genus of claimed promoters because the art taught that cell cycle-dependent expression in one type of cell was not predictive of activity in another cell type. Id. at 8. Thus, while cell cycle-dependent promoters were well known in the art, the appellant could not rely on that fact because a skilled artisan could not predict whether a given promoter would achieve the claimed function across various cell types. Id. at 8-10.
The Board, therefore, ultimately found that the appellant’s claim scope outsized the breadth of description in the specification, given the hundreds of potential promoters in the art subsumed by the term “cell-cycle dependent promoters” and the unpredictability in expression between cell types. Id.
Conclusion
The foregoing cases represent only a snapshot of PTAB decisions addressing § 112 in patents and applications directed to the life sciences. Despite the swath of recent case law from the Federal Circuit and Supreme Court addressing § 112, the Board still routinely applies cases like Ariad and Idenix when assessing genus claims, and considers whether the specification discloses a representative number of species or common structural features among the members of the claimed genus. Parties should also be mindful of the critical date for assessing § 112 support in a specification as a priority challenge (measured from the priority date) or as a challenge to patentability (measured from the application’s effective filing date).
[1] While the PTAB addressed § 112 issues in many other decisions in 2025, this article highlights cases in the life sciences.
This article appeared in the 2025 PTAB Year in Review: Analysis & Trends report.
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