Even Jepson Preambles Require Written Description Support | McDermott Will & Emery
The US Court of Appeals, Federal Circuit, found that a Jepson claim was not patentable because the specification did provide an adequate written description of the portion of the Jepson claim that purported to recite what had been well known in prior art. In re Xencor, Inc., Case No. 24-1870 (Fed. Cir. Mar. 13, 2025) (Hughes, Stark, Schroeder, JJ. The application included:
A Jepson claim reciting, “
- n a method of treating a patient by administering an anti-C5 with an Fc domain, the improvement comprising” certain amino acid substitutes wherein the modified antibody has “increased in vivo half-life.”[i]A non-Jepson claim directed to “a method of treating a patient by administering an anti-C5 antibodies comprising” certain amino acid replacements, where The application included:
- A Jepson claim reciting, “
n a method of treating a patient by administering an anti-C5 antibody with an Fc domain, the improvement comprising” certain amino acid substitutions, wherein the modified antibody has “increased in vivo half-life.”
A non-Jepson claim directed to “a method of treating a patient by administering an anti-C5 antibody comprising” certain amino acid substitutions, wherein the modified antibody “has increased in vivo half-life.”
The specification provided one example of an anti-C5 antibody, 5G1.1, and three high-level examples of potential uses for anti-C5 antibodies. The examiner rejected claims due to a lack of written descriptions. Xencor appealed unsuccessfully the rejection at the Patent Trial & Appeal Board. Xencor appealed to the Federal Circuit, which resulted in a remand to the Board’s Appeals Review Panel (ARP). Xencor appealed the decision to the Federal Circuit which resulted a remand back to the Board’s Appeals Review Panel. Xencor appealed again, arguing that treating a patient was not limiting, and that Jepson claim preambles don’t require written description support.
With regard to the preamble for the method claim, Federal Circuit noted that Xencor acknowledged that the “administering ” portion was limiting, but argued that “treating a patients” was non-limiting. The Court noted that although a preamble may be divided into limiting and not-limiting portions, it could not be easily separated in this case because the phrase “treating patient” was directly linked to the phrase of “administering anti-C5 antibodies” through the word “by,” and both phrases had meaning. The Court agreed with the ARP that the recitation “treating a patient” was limiting. Accordingly, the Court agreed with the ARP that the recitation “treating a patient” was limiting.
The Federal Circuit next concluded that substantial evidence supported the ARP’s determination that the specification did not provide written description support for “treating a patient.” Because the specification was not limited to treating a particular disease, “treating a patient” meant “treating all patients and all diseases.” While the specification provided three examples of classes of diseases that might benefit from the claimed treatment, the Court agreed with the ARP that this disclosure was inadequate to demonstrate possession of a method of treating any particular disease, let alone all diseases.
Finally, the Federal Circuit explained that a Jepson claim preamble requires written description support because it is used to define the claimed invention and the claim scope. The Court warned that a Jepson preamble is required to define the claimed invention and the claim scope. Otherwise, a patentee would be able to obtain a Jepson with a preamble reciting a time-machine as well known in art without describing a machine. The applicant must prove that the claim of being well-known in the art is actually well-known in the art to provide an adequate written description in a Jepson case. The Court explained that the amount of disclosure necessary varies depending on the level of knowledge of the person skilled in the art, the unpredictability of the art, and the newness of the technology.
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Given the large number of possible antibodies in the anti-C5 antibody genus and the limited disclosure in the specification, the Federal Circuit affirmed the ARP’s determination that the Jepson claim lacked adequate written description.01001010
