The Federal Circuit recently held that the written description requirement extends to the limiting preamble of a Jepson claim. In In re Xencor, Inc., Appel No. 2024-1870 (Fed. Cir. Mar. 13, 2025), the court affirmed the PTO’s written description rejections of a claim written in Jepson form where the specification failed to describe portions of the preamble that were alleged to be well-known. In doing so, the Court resolved the parties’ dispute as to whether the “invention” of a Jepson claim for purposes of 35 U.S.C. § 112 is limited to only the alleged improvement (Xencor’s position) or instead extends to the complete claim, including the conventional aspects in the preamble (the PTO position). The Federal Circuit determined that the PTO’s position was correct.
Procedural Background
In re Xencor came to the Federal Circuit on appeal from rejections of claims in a Xencor patent application. Relevant here, the preamble of claim 8 recited, “In a method of treating a patient by administering an anti-C5 antibody with an Fc domain, the improvement comprising.” Xencor and the PTO agreed that the claim was written in Jepson form. The “Jepson” appellation, which derives from the case recognizing the propriety of such claiming format, describes claims that contain (1) a preamble with a general description of elements or steps that are convention or known, (2) a phrase such as “wherein the improvement comprises”, and (3) elements or steps that constitute the allegedly new or improved portion of the claimed combination. The Examiner rejected claim 8 as lacking written description under 35 U.S.C. § 112. Xencor appealed the rejection (among others not relevant here) to the Patent Trial and Appeal Board, which issued a decision affirming the Examiner’s rejection. Xencor appealed the decision to the Federal Circuit. After Xencor filed its opening brief, the PTO moved to have the case remanded so that the Appeals Review Panel (“ARP”) of the PTO could “clarify” certain of the PTO’s positions. The Federal Circuit granted the motion, and the ARP thereafter issued its decision, again maintaining the written description rejection of claim 8.
Federal Circuit Decision
The Federal Circuit affirmed the ARP. With respect to claim 8, the Federal Circuit agreed with the ARP that the written description requirement extends to the entire extent of a Jepson claim, including the allegedly conventional or known aspects recited in the preamble. The Federal Circuit held that “when the Jepson form is employed, the claim preamble is used to define the claimed invention, thereby limiting claim scope.” In other words, the court held that the “invention” of a Jepson claim is the totality of what is set out in the claim. The Federal Circuit rejected Xencor’s argument that the “invention” of a Jepson claim is only the improvement. Rather, according to the Federal Circuit, the invention is “the claimed improvement as applied to the prior art.” The Federal Circuit’s decision further noted that its holding would prevent potential “abuse.” In particular, the court held that “[a] patentee cannot be permitted to use a Jepson claim to avoid the requirement that she be in possession of the claimed invention, simply by asserting something is well known in the art.” Adoption of Xencor’s position, according to the court, would have left the patent system vulnerable to such exploitation. Xencor had not argued that the preamble of claim 8 found written description support in the specification; thus, the Federal Circuit’s legal holding as to the written description requirement was dispositive with respect to claim 8.
The Federal Circuit emphasized that what constitutes sufficient written description is a case-by-case determination. Thus, while the focus of the written description inquiry is on the patent (or application) itself, a finder of fact “may consider evidence outside the patent to understand what a person of ordinary skill in the art would have known as of the pertinent date.” To illustrate this, the court used an analogy that may have been prompted by Xencor’s opening brief. The court stated that the use of the term “automobile” in the nineteenth century would have required extensive explanation in the specification; however, the term likely would not require any support in a patent today. That may have been the court’s (indirect) response to a concern that Xencor raised in its opening brief. Xencor argued that a hypothetical claim directed at an improved steering wheel may begin as follows: “In a four-wheeled vehicle, the improvement comprising a novel steering wheel.” According to Xencor, an inventor of such a claim should not be required to provide written description support for the entire genus of four-wheeled vehicles (including cars, trucks, vans, etc.). In view of the Federal Circuit’s holding in In re Xencor, an inventor indeed may not have to describe the entire breadth of the preamble when the preamble includes ubiquitous matter such as automobiles. However, that is not a suspension of the written description requirement but rather another way of satisfying it.
Conclusion
The In re Xencor decision establishes that written description challenges can be made to all aspect of Jepson claims, including their preambles. As with all such challenges, the inquiry will consider not only the matter specifically described in the specification but the knowledge of a skilled artisan as well.