The PTAB Axes Skin Treatment Patent Under Amgen

The Patent Trial and Appeal Board ("PTAB") recently invalidated a University of Massachusetts ("UMass") patent related to the treatment of the skin disease vitiligo in a post-grant review. (SeeForte Biosciences Inc v. University of Massachusetts, PGR2023-00014.) The PTAB found UMass's claims directed to methods of treating vitiligo with a functionally defined genus of compounds failed to meet enablement and written description requirements. Enablement of genus claims was addressed by the Supreme Court in last year's Amgen case. (See Amgen v. Sanofi, 598 U.S. 594). Importantly, this PTAB decision demonstrates that method claims are not insulated from the Amgen ruling, stating that "the specification must provide some guidance regarding structure for a recited element of the claim."

Forte Biosciences, Inc. ("Forte") challenged the patentability of claims 1-5 on enablement, written description, and obviousness grounds.

Claim 1 is illustrative of the challenged claims and is shown below.

1. A method of treating a subject who has a vitiligo lesion, the method comprising: identifying a subject in need of treatment; and administering a therapeutically effective amount of an inhibitor of IL-15 or the IL-15 receptor to the subject.

The PTAB found the challenged claims unpatentable for lack of enablement and written description under 35 U.S.C. § 112(a). The PTAB did not reach the obviousness challenge.

The PTAB's Post-AmgenEnablement Analysis

In deciding whether the challenged claims are enabled under 35 U.S.C. § 112(a), the PTAB applied the Amgen court's analysis regarding genus claims encompassing entire classes of functionally defined compounds and considered the Wands factors to determine whether undue experimentation is required to make and use the claimed invention. Amgen v. Sanofi, 598 U.S. 594.

The Amgen court held that, "[i]f a patent claims an entire class of processes, machines, manufactures, or compositions of matter, the patent's specification must enable a person skilled in the art to make and use the entire class." Amgen, at 610. Essentially, "[t]he more one claims, the more one must enable." Id. This concept of quid pro quo is at the heart of the U.S. patent system.

The PTAB determined that the inhibitors claimed in the UMass's patent are even broader than the genus of antibodies at issue in Amgen, as neither the specification nor the claims of the UMass's patent provide any structural requirement for the claimed inhibitors. Forte Biosciences, at 30. For instance, claim 2 of the UMass's patent states that inhibitors can be small molecules, antibodies, peptides, or nucleic acids, none of which share any common structural features. Id. at 30-31. Due to the complicated and unpredictable nature of IL-15/IL-15R inhibition, the PTAB rejected UMass's argument that IL-15/IL-15R inhibitors and their mechanisms were well known in the art and held that a skilled person would have to engage in extensive experimentation to identify and test each compound covered by the claim scope to determine whether the compound works.

Furthermore, the PTAB also rejected UMass's argument that the challenged claims are directed towards methods of treatment for vitiligo instead of the inhibitors for IL-15 or IL-15R themselves, thereby avoiding the "how to make" requirement for the inhibitors. The PTAB held that, if a challenged claim recites a functionally defined genus of compounds, as is the case with UMass's method of treatment claims, "the specification must provide some guidance regarding structure for a recited element of the claim[.]" Id. at 37. This is to prevent a skilled person from having to engage in extensive trial and error to determine which compound falls within the claim scope. Id. Consequently, the PTAB found the challenged claims were unpatentable due to lack of enablement.

The PTAB's Written Description Analysis of Genus Claims

The PTAB agreed with Forte's characterization that the challenged claims were directed broadly to methods of treating vitiligo by administering an inhibitor of IL-15 or IL-15R in a therapeutically effective amount, while UMass's patent only disclosed a single working example, i.e., ChMBC7, which is an antibody inhibitor targeting a mouse protein, IL-2R β/IL-15R β.

Furthermore, the PTAB rejected UMass's argument that, because the challenged claims are method claims and not composition of matter claims, the written description inquiry should only consider whether the patentee possessed the claimed methods of administering a therapeutically effective amount of an inhibitor to treat vitiligo, rather than whether the patentee possessed the entire genus of the claimed inhibitors. Forte Biosciences, at 16-17. The PTAB emphasized that, regardless of whether a claim is for a compound itself or a method involving the compound, the patentee must provide a description detailed enough to differentiate infringing compounds or methods from non-infringing ones. Id. at 16. Thus, the PTAB found UMass's contention unpersuasive.

Additionally, the PTAB agreed with Forte that UMass's patent lacked descriptive support for the challenged claims because the evidence showed: (1) that not all IL-15 or IL-15R inhibitors are therapeutically effective; (2) that the specification does not disclose structural features of the IL-15 or IL-15R inhibitors necessary or sufficient to perform the claimed methods; (3) a lack of information to allow a skilled artisan to understand or determine whether an inhibitor actually meets the functional requirement in the challenged claims; and (4) unpredictability across the breadth of the claimed genera (e.g., small molecules, peptides, antibodies, or nucleic acids).

In sum, the PTAB found that the challenged claims are directed to methods using a wide range of different types of compounds that are not part of a known or readily identifiable class, do not target the same biological pathway, do not have any common structural features, and do not always function as inhibitors. Hence, the PTAB held that UMass's patent did not disclose a representative number of species or a sufficient correlation between structure and function to demonstrate possession of the claimed methods of treatment using a functionally defined genus of compounds.

Takeaways

This recent PTAB decision underscores the importance of enablement and written description considerations for functionally defined genera recited in method claims under Amgen. The broad nature of claims containing functionally defined genera inherently increases the difficulty of meeting the enablement requirement across the full scope of the claims. Similarly, the written description requirement mandates that claims must be supported by what is described in the specification. Therefore, practitioners may strategically consider the inclusion of functional limitations in method claims and contemplate multiple backup positions with varied claim scope in view of the enablement and written description requirements.

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