On May 17, 2024, an Appeals Review Panel (ARP) of the United States Patent and Trademark Office (“USPTO”) released its decision in Ex parte Chamberlain (referred to in Federal Circuit proceedings as In re Xencor; “Chamberlain”). The Chamberlain decision provides some clarity on the USPTO’s position on written description requirements for Jepson and means-plus-function claims in the life sciences space. Importantly, it suggests that carefully drafted means-plus-function claims are a potential path for Applicants to claim antibodies broadly by use of functional language (i.e., by their targets) once again.
The two claims considered in Chamberlain are functional claims to an antibody styled as (a) a Jepson claim (claim 8) and (b) a means-plus-function claim (claim 9). In the Chamberlain decision, officially dated May 21, 2024, the ARP maintains the Patent Trial and Appeal Board’s (“PTAB”) rejection of both claims for lack of written description, reverses the rejection of claim 9 for indefiniteness, and reverses the Examiner’s obviousness-type double patenting rejections of claims 8 and 9 (not addressed in this publication).
Claims at Issue
The ARP addresses the two pending claims of U.S. Patent Application No. 16/803,690 (the “’690 application”). Both claims relate to use of anti-C5 antibodies with a modified Fc domain. The Applicant drafted the claims in the Jepson and means-plus-function claim formats (claims 8 and 9, respectively):
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 substitution 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 substitution 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 substitution 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 substitution has increased in vivo half-life as compared to said antibody without said substitutions.
Procedural History
During prosecution of the claims, the primary Examiner rejected both claims as unpatentable for failing to comply with the written description requirement (35 U.S.C. § 112, first paragraph), and under the obviousness-type double patenting doctrine. The Examiner also rejected claim 9 as indefinite (35 U.S.C. § 112, second paragraph). The Applicant, Xencor, Inc. (“Xencor”), appealed the rejection to the PTAB, after which the Examiner withdrew the written description rejections.
In its decision, the PTAB reinstated the written description rejections and upheld the rejections maintained by the Examiner. Xencor appealed to the Federal Circuit. Following the filing of Xencor’s appeal brief, the Director of the USPTO filed a motion for remand back to the USPTO “to permit further consideration and issuance of a revised decision by the Appeals Review Panel.” The Director’s motion for remand stated that:
Xencor’s pending claims present novel questions involving the application of the Supreme Court’s and this Court’s precedent for both Jepson-format and means-plus-function claims in the field of biotechnology, and in particular the antibody art. The use of Jepson format and means-plus-function claims in the life sciences is exceedingly rare. Therefore, the USPTO seeks remand in order to issue a revised decision that clearly and thoroughly expresses the Agency’s view on application of the case law to this important area of technology.
Xencor opposed the USPTO’s request as arising too late. On January 23, 2024 the Federal Circuit issued its decision, remanding the case back to the USPTO. On March 15, 2024 the Federal Circuit mandate issued, 7 days after the period for filing a petition for rehearing expired.
The ARP’s Chamberlain decision maintains the written description rejections. With respect to the means-plus-function claim, instead of focusing on the antibody element, the Chamberlain decision focuses on the preamble’s recitation of “a method of treating” as lacking sufficient written description.
Claim 8 (the Jepson claim)
The ARP first addresses whether preamble of claim 8 is limiting on the body of the claim. The preamble of claim 8 is “In a method of treating a patient by administering an anti-C5 antibody with an Fc domain.” During the PTAB proceedings, the PTAB found that the preamble was limiting and, therefore, that 35 U.S.C. § 112, first paragraph (written description) applied to the preamble. Xencor had argued to the PTAB that the preamble was not limiting.
As noted in the Chamberlain decision, “a claim in Jepson form recites a preamble that sets forth what is impliedly admitted to be prior art, followed by the body of the claim, which describes a recited improvement, with the two parts separated by a transitional phrase such as ‘wherein the improvement comprises.’” The Chamberlain decision holds that “The preamble of a Jepson claim is limiting, by necessity, because it defines the scope of the claim.”
The Chamberlain decision also notes that even absent precedent establishing that the preamble of a Jepson claim is limiting, “we would still conclude that the entire preamble of claim 8 is limiting under the more general case law guiding the construction of claim preambles.” The Chamberlain decision states, “claim 8 includes limitations directed to ‘said Fc domain’ and ‘said anti-C5 antibody’ [and] that each find their antecedent basis in the [preamble].” Further, the Chamberlain decision notes that an element of the claim is the antibody having an increased in vivo half-life, and that element only makes sense in the context of administering the antibody to a patient. Thus, the Chamberlain decision concludes the preamble was necessary to give “life, meaning, and vitality” to the claim.
The Chamberlain decision construes “treating a patient by administering” as encompassing "treating any patient having any disease or condition." It further construes “patient” to include both human and non-human animals.
Following discussion of claim construction, the Chamberlain decision turns to whether the elements of the preamble satisfy the written description requirement. The Chamberlain decision holds that the single anti-C5 antibody disclosed in the specification does not provide sufficient written description for the entire genus of anti-C5 antibodies. The Chamberlain decision also holds that the specification does not provide sufficient written description for “treating any patient having any disease or condition.” The Chamberlain decision notes the following:
The Specification does not describe what patients with what diseases or conditions can be successfully treated with an anti-C5 antibody possessing the claimed Fc 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.
The Chamberlain decision concludes that the specification as filed does not provide adequate written description to support the genus of anti-C5 antibodies nor the genus for "treating a patient," maintaining the PTAB’s rejection of claim 8 for lack of written description.
Claim 9 (the means-plus-function claim)
Means-plus-function claims are governed by 35 U.S.C. § 112, paragraph 6. The statute provides:
An element in a claim for a combination may be expressed as a means or step for performing a specified function without the recital of structure, material, or acts in support thereof, and such claim shall be construed to cover the corresponding structure, material, or acts described in the specification and equivalents thereof.
As it does with claim 8, the Chamberlain decision first addresses whether the preamble of claim 9 is limiting on the body of the claim. Using the same rationale as used in interpreting claim 8, the Chamberlain decision finds that “treating a patient” “is an intended purpose of the claim that is limiting [on the body of claim 9].”
The Chamberlain decision acknowledges that the claim is a proper means-plus-function claim, writing that “one cannot reasonably understand the claim phrase ‘means for binding human C5 protein’ to have a sufficiently definite meaning as the name for structure because it merely recites the function of binding to human C5 protein.”
Because “means for binding human C5 protein” is interpreted as a means-plus-function claim term, 35 U.S.C. § 112, paragraph 6 requires only that the specification provide a single corresponding structure clearly linked to the function of binding human C5 protein. The Chamberlain decision holds that the single example provided in the specification (antibody 5G1.1) is enough to satisfy the statutory requirement. The Decision also holds that 35 U.S.C. § 112, paragraph 6 does not require the specification describe “equivalents” of the means-plus-function element. In the Chamberlain decision the ARP states that while a means-plus-function element “is interpreted to cover both the corresponding structure… described in the Specification, as well as equivalents of that structure… ,” “the statute clearly distinguishes between what must be ‘described in the specification’ and ‘equivalents’.” Thus, the Chamberlain decision holds that there is proper written description supporting “means for binding human C5 protein,” and that the claim is not indefinite.
However, for the same reasons used to reject claim 8, the Chamberlain decision holds that there is not sufficient written description for the genus for "treating a patient," thus, maintaining the PTAB’s rejection of claim 9 for lack of written description.
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