Written Description is Required When a Preamble is Limiting
| March 26, 2025
IN RE: XENCOR, INC
Date of decision: March 13, 2025
Panel: before Hughes, Stark and Schroeder (District Judge (Eastern District of Texas) sitting by designation), Opinion by Schroeder
Background
This precedential decision is from an appeal by Xencor from a decision by the Appeals Review Panel (ARP). The ARP was established July 24, 2023. The ARP may be convened by the Director sua sponte to review decisions of the Patent Trial and Appeal Board (PTAB or Board) in ex parte appeals, re-examination appeals, and reissue appeals.
The application at issue is 16/803,690, which is a continuation application having an earliest priority date of February 25, 2008. Claim 8 (a Jepson claim) and claim 9 are at issue:
8. In a method of treating a patient by administering an anti-C5 antibody with an Fc domain, the improvement comprising
said Fc domain comprising amino acid substitutions M428L/N434S as compared to a human Fc polypeptide,
wherein numbering is according to the EU index of Kabat,
wherein said anti-C5 antibody with said amino acid substitutions has increased in vivo half-life as compared to said antibody without said substitutions.
9. A method of treating a patient by administering an anti-C5 antibody comprising:
a) means for binding human C5 protein; and
b) an Fc domain comprising amino acid substitutions M428L/N434S as compared to a human Fc polypeptide,
wherein numbering is according to the EU index of Kabat, wherein said anti-C5 antibody with said amino acid substitutions has increased in vivo half-life as compared to said antibody without said substitutions.
The Examiner had rejected the claims as lacking written description. Xencor appealed to the Patent Trial and Appeal Board. The Board held that the preambles of the claims are limiting, and that Xencor had not shown that the application contained a sufficient written description for either claim. The Board decision also determined that Xencor had not shown that anti-C5 antibodies or methods of treating patients with anti-C5 antibodies were well-known in the art at the time of invention.
Xencor petitioned for reconsideration, and the Board again found against Xencor for the same reasons. Xencor appealed to the CAFC. Prior to being heard, the Patent Office requested remand to the ARP (presumably to address the preamble).
The decision of the ARP addressed whether written description was required for Jepson claim preambles. It found that Jepson preambles define the scope of the claim, and therefore a written description is required. The ARP found the preamble language “treating a patient” as limiting because it was necessary to give life, meaning, and vitality to both limitations “increased in vivo half-life” and “administering” (the sole method step).
The ARP decision then concluded the claims did not have sufficient written description. The specification did not provide a representative number of species to support the broad genus of anti C5 antibodies being claimed. The specification only disclosed one anti-C5 antibody (5G1.1). The ARP also adopted the Board’s findings that Xencor’s expert was not credible and that Xencor had not demonstrated that anti-C antibodies were well-known (in which case not requiring further support in the specification).
The ARP decision also found that “treating a patient” was not supported by an adequate written description since the specification does not describe what patients with what diseases or conditions can be successfully treated with an anti-C antibody.
Xencor appealed the decision of the ARP to the CAFC.
Discussion
The Director stated that the CAFC’s standard of review of ARP’s decisions is the same as for decisions from the Board. As such, legal determinations are reviewed de novo, while factual findings are reviewed for substantial evidence.
Xencor argues that the preamble “treating a patient” is not limiting, that the preamble of a Jepson claim does not require written description, and, in the alternative, written description was satisfied for the preambles of both claims.
Claim 9
With respect to a “method of treating a patient by administering an anti-C5 antibody”, Xencor argues the different sections of the preamble should be treated independently, that is “treating a patient” and “administering an anti-C5 antibody”, where the “treating a patient” is not limiting. As such, Xencor argues that only “administering an anti-C5 antibody” should be considered limiting.
The CAFC agreed with the Director that “treating a patient by” is limiting. The CAFC first noted that Xencor does not dispute that “administering an anti-C5 antibody” should be considered limiting. The CAFC noted that the phrases are connected by the term “by” which gives credence to the argument that the entire preamble should be considered limiting. The “treating a patient” is done by administering the anti-C5 antibody, which is not a mere statement of purpose or a statement of intended result. In addition, since the claim does not require a dosage and rate, a person of ordinary skill in the art would have read the claim language of “increased in vivo half-life” in conjunction with “treating a patient” in order to make sense. Still further, the preamble provides a “raison d’etre” (reason for being) for the claim. An increased in vivo half-life only makes sense with respect to a living being (otherwise it cannot be in vivo) and has a specific utility with respect to treatment. Lastly, the specification teaches longer in vivo half-lives allow more seldom injections such that the specification “gives further color to the language of the claims and the understanding we have of the language as limiting.”
The CAFC then considered whether the specification satisfied the written description requirement. No specific amount of efficacy is claimed, so no specific amount is required in the specification. The application does not define the meaning of “treating” and does not provide any data associated with treating any patient with any disease or condition with any anti-C5 antibody. As such, the specification does not limit the treatment to any specific disease. As such, “treating a patient” means “treating all patients and all diseases”. At best, the disclosure of three classes of diseases/conditions that might benefit from administration of various antibodies with an Fc modification and lists various unmodified antibodies that could be modified and used to that end. Such disclosure is found to be “inadequate to demonstrate possession of a method of treating any particular disease/condition with the claimed anti-C5 antibodies, let alone all diseases/conditions within the three enumerated classes.”
Xencor had argued that the claim does not require the treatment to be effective. However, the ARP merely required that the applicant had possession of a method of treating a patient with 5G1.1 and its equivalents and found that it did not.
Claim 8
Claim 8 raises the question of whether a Jepson claim requires written description since the preamble of a Jepson claim defines what the prior art is, followed by recitation of what the improvement is. Xencor argues that a written description is only needed for the improvement.
Under 35 U.S.C. 112, a specification must contain a written description of the invention. This requirement must “be met in some way so as to describe the claimed invention so that one skilled in the art can recognize what is claimed.”
Such a description is context-specific: “[T]he level of detail required to satisfy the written description requirement varies depending on the nature and scope of the claims and on the complexity and predictability of the relevant technology.” Ariad Pharms., Inc. v. Eli Lilly & Co., 598 F.3d 1336, 1351 (Fed. Cir. 2010); see also Univ. of Rochester, 358 F.3d at 923 (explaining that merely stating “automobile” in a claim would not have been sufficient written description at the time of invention of the automobile).
In a Jepson claim, the preamble is used to define the invention, thereby limiting the claim scope. The invention is not only the improvement but also the improvement as applied to the prior art. Simply asserting that something is well known in the art is not sufficient to show that the inventor had possession of the claimed invention. The CAFC gave an example:
For example, a patentee cannot obtain a Jepson claim with a preamble that says that a time machine is well-known in the art without describing a time machine, in sufficient detail to make clear to a person of ordinary skill in the art that the inventor is in possession of such a time machine. Adoption of Xencor’s position would leave the patent system vulnerable to such abuse.
Thus, an adequate written description for a Jepson claim requires the applicant to establish what is claimed to be well-known in the art is, in fact, well known in the art.
Takeaway
Claims need to be supported by a written description as required by 35 U.S.C. 112, including the preamble when the preamble is considered limiting.
Do not include language in a preamble of a Jepson claim if it is not well-known or not supported by the specification. For this application, perhaps simply stating a method of administering an anti-C5 antibody could have avoided the written description problem, but perhaps this could lead to other issues such as enablement.
At the time the specification was filed in 2008, the specification stated “the exact dose will depend on the purpose of treatment” and the characteristics of the patient. This likely raises questions whether the inventor was in possession of the claimed invention (treating all patients with all diseases).
