USPTO ARP Panel Restores MPF Sanity, but Still Rejects Xencor’s Claims

by Dennis Crouch
In a new Appeals Review Panel (ARP), the USPTO has clarified the Office’s position on means plus function claims — explaining that the specification need not describe statutory equivalents to satisfy the written description requirement.  The outcome here shows value for the intentional use of means-plus-function limitations as a mechanism for expanding patent scope when genus claims are otherwise unavailable.
Still the court maintained the written description rejection on other grounds — finding that the broad preamble “method of treating a patient” to be limiting and not adequately supported by the specification.  Perhaps on remand the patentee will amend the preamble to instead claim a “means of treating a patient.” 
The decision will be captioned Ex parte Chamberlain , Appeal 22-1944 , and is post-dated May 21, 2024.  The decision comes after the Federal Circuit remanded the case, then known as In re Xencor, Inc. , back to the USPTO to reconsider its approach to both the MPF issue as well as a parallel written description issue for Jepson claim preambles. Although not directly related, the Supreme Court’s May 18, 2023 decision in Amgen v. Sanofi is related because it affirmed a high bar to antibody genus claims based upon the enablement doctrine. Even before the decision, biotech -focused patent attorneys have been searching for ways to capture their clients innovations with broad enough coverage.
Xencor’s patent application (U.S. Application No. 16/803,690) includes claims directed to methods of treating patients by administering optimized IgG immunoglobulin variants.  The basic underlying issue in the case is that the patentee would like to broadly claim all “anti-c5 antibody” having certain structural features, but the specification only discloses one particular example known as 5G1.1, although in both a murine (mouse-derived) version and its humanized form, eculizumab.
Representative claim 8 is drafted in Jepson format with the preamble at issue underlined.  The basic idea here was to put the anti-C5 antibody limitation into the preamble of the Jepson claim that sets up the environment of the invention, but is not actually the improvement being claimed.  Xencor’s idea is that the Jepson preamble should not require the same level of written description support because it is often seen as non-limiting.
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.
Claim 9 uses means-plus-function language, with the relevant portion underlined.  The idea here is to claim the anti-C5 antibody in MPF form rather than structurally. Thus, it is claimed as a “means for binding human C5.”  Under Section 112(f), the claim is interpreted to cover the structure disclosed in the specification along with its equivalents. Thus this should cover the disclosed 5G1.1 and its equivalents.
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 Board found that both claims lacked written description support.  In the ARP decision, the Director has maintained that finding.
The case has a unique procedural history. The examiner initially rejected the claims for lack of written description under 35 U.S.C. § 112(a), but withdrew those rejections during the appeal process. The Patent Trial and Appeal Board (PTAB) then entered new grounds of rejection for lack of written description and indefiniteness. The PTAB found the preamble of the Jepson claim limiting and requiring written description support.  Xencor had cited contrary precedent suggesting that Jepson preambles were not limiting.  Regarding means-plus-function, recall that MPF claim limitations are interpreted to cover both the structure disclosed in the specification and its equivalents.  In a quirky decision, the Board concluded that, since the claim covers equivalents, it must also adequately describe those equivalents in order to satisfy the written description requirement. Xencor appealed to the Federal Circuit. Before the Federal Circuit could rule on the merits, the USPTO Director filed an opposed motion requesting a remand to allow the ARP to clarify the Office’s position. The Federal Circuit granted the remand, noting its expectation “that proceedings will be conducted expeditiously.” In re Xencor, Inc. , No. 2023-2048 (Fed. Cir. Jan. 23, 2024).
The new ARP decision is listed as per curium, but comes directly from the USPTO Director Kathi Vidal along with the Commissioner for Patents Vaishali Udupa and Chief Administrative Patent Judge Scott Boalick.
Jepson Claims : In its decision, the ARP relied heavily Federal Circuit precedent interpreting 35 U.S.C. § 112. Regarding Jepson claims, the panel cited Rowe v. Dror , 112 F.3d 473 (Fed. Cir. 1997) and Epcon Gas Sys., Inc. v. Bauer Compressors, Inc. , 279 F.3d 1022 (Fed. Cir. 2002) for the proposition that “the preamble of a Jepson claim is limiting, by necessity, because it defines the scope of the claim.” Having found the Jepson preamble limiting, the ARP also agreed with the PTAB that disclosure of a single anti-C5 antibody (5G1.1) was insufficient to describe the full genus of anti-C5 antibodies encompassed by the claims.
Means Plus Function : Turning to the means-plus-function claim, the ARP relied on the plain language of 35 U.S.C. § 112(f) to conclude that the specification need only describe the corresponding structure, not equivalents thereof, to satisfy the written description requirement.  The ARP explained that “Section 112(f) clearly distinguishes between what must be ‘ described in the specification’ and ‘equivalents.'” (emphasis added by ARP).  The panel found that disclosure of antibody 5G1.1 provided sufficient corresponding structure for the claimed function of “binding human C5 protein.”
Treating a Patient : However, apart from these Jepson and MPF elements, the the panel found that both claim preambles included a major written description problem.  The ARP concluded that under normal claim construction principles, the preamble phrase “treating a patient” is limiting because it “gives life, meaning, and vitality” to the claimed method.  Treating a patient is not merely a statement of intended use, but it is central to the invention’s purpose.  and, the specification failed to describe treating all patients for all diseases, as broadly recited in the preamble.
The specification had broadly defined patients and conditions being treated, including humans and non-humans, and for the treatment of “autoimmune, inflammatory, or transplant indications.”  The court concluded that this broad scope was not supported by the Specification.
On the facts of this case, the claim language of “treating a patient,” without specifying the type of patient and/or the type of disease to be treated, is overbroad. The Specification does not describe what patients with what diseases or conditions can be successfully treated with an anti-C5 antibody possessing the claimed Fe modifications. Nor is there a single working example describing treatment of patients with a disease or condition with an anti-C5 antibody possessing the claimed Fe modifications. At best, the Specification lists three classes of diseases/conditions that might benefit from administration of various antibodies with an Fc modification, and lists various unmodified antibodies, including an anti-C5 antibody (5G1.1), that could be modified and used to that end.
That limited disclosure is 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 or all diseases/conditions more generally, including those that affect non-human patients. And even if we were to credit the mention of the three enumerated classes of diseases/conditions as adequate written description, we find that the enumerated classes of diseases, which were disclosed in the only embodiment mentioning anti-C5 antibodies, are not representative of the scope of the claimed genus, i.e., all diseases, nor does the Specification provide features common to all members of the genus such that one of skill could recognize all diseases that are encompassed.
In justifying its decision, the ARP emphasized the need to ensure that patent claims do not “overreach the scope of the inventor’s contribution to the field of art as described in the patent specification.”  quoting Ariad Pharms., Inc. v. Eli Lilly & Co. , 598 F.3d 1336 (Fed. Cir. 2010).
It would discourage invention of new uses for known compounds if an applicant can obtain a broad claim for “treating a patient,” i.e., any patient, having any disease or condition (for all uses of a compound) without providing written description support (and enablement) therefor, depriving the public of their part of the bargain struck in our patent laws. Thus, it is preferable to require a claim to recite treatment of a specific disease or condition, such as “treating headache,” as recited in the claim in Eli Lilly ,
rather than claiming a treatment without limitation, unless “treating a patient” can be adequately supported for all patients and all diseases without limitation.
In the end, the ARP decision restores important clarity to interpretation and power of means-plus-function claims, but still shows that broad method of treatment claims are not easy to come by for biotech innovators.