Drugmakers and other companies in the life sciences industry seeking to invalidate patents have another arrow in their quiver thanks to a recent federal court decision.

In late March, the U.S. Court of Appeals for the Federal Circuit in Xencor Inc. affirmed a decision from the Patent Trial and Appeal Board (PTAB) that the biotech company Xencor Inc. failed to provide an adequate written description for its Jepson claim and another claim to support its application for an antibody patent. The court agreed that Xencor’s claims had limiting preambles because they were written in Jepson format — and include a preamble that specifies what was known in the prior art as well as a description of how the claimed invention improves upon it. 

As companies look at challenging drug patents listed in the patent and exclusivity information addendum of the FDA’s publication, "Approved Drug Products With Therapeutic Equivalence Evaluations" (commonly known as the "Orange Book"), the recent decision adds another vulnerability they can explore when challenging the validity of those patents. 

What the Federal Circuit Ruled On

Xencor appealed a decision by the PTAB that rejected Xencor’s patent claims for lack of written description. The court held that the preamble of a Jepson claim must be supported by sufficient written description in the patent specification, which varies based on the knowledge of a person skilled in the relevant art.  The preamble of the subject Jepson claim read as follows: "In a method of treating a patient by administering an anti-C5 antibody with an Fc domain, the improvement comprising."  

The PTAB and the Appeals Review Panel (ARP) both found that Xencor's specification did not provide a representative number of species to support the broad genus of anti-C5 antibodies claimed. The ARP also found that the specification did not describe what patients or diseases could be treated with the claimed antibodies, nor did it provide any working examples. The Federal Circuit agreed with the ARP that the preamble language "treating a patient" is limiting and requires adequate written description, which Xencor's application did not satisfy.

Citing the statutory requirement that a patent specification must "contain a written description of the invention … , in such full, clear, concise, and exact terms as to enable any person skilled in the art to which it pertains, or with which it is most nearly connected, to make and use the same," the Federal Circuit reiterated its precedent that the level of detail required to satisfy this requirement "varies depending on the nature and scope of the claims and on the complexity and predictability of the relevant technology."  

The court then explained that for Jepson claims, "[t]he invention is not only the claimed improvement, but the claimed improvement as applied to the prior art, so the inventor must provide written description sufficient to show possession of the claimed improvement to what was known in the prior art." The court held that in order "to provide adequate written description for a Jepson claim, the applicant must establish that what is claimed to be well-known in the prior art is, in fact, well-known in the prior art" and affirmed the ARP’s ruling of inadequate written description.  

Potential Implications for Life Sciences and Pharmaceutical Companies

Following the Supreme Court’s earlier 2023 decision in Amgen Inc. v. Sanofi clarifying the enablement requirement of written description in the context of antibodies, the Federal Circuit’s recent Xencor decision demonstrates that patents relating to biologic products like antibodies have a high bar to clear with regard to written description and enablement. 

In Amgen, the Supreme Court concluded that Amgen’s broad claims to antibodies based on their function were not enabled by the examples provided in the patent, when there was no general quality running through the claimed class that showed their applicability for the claimed purpose. Amgen argued that its claims were enabled because a person of ordinary skill in the art would be able to find functional antibodies by making and testing new antibodies to see if they had the claimed functionality. The Supreme Court explained that this approach was simply requiring others to undertake their own research projects, not enabling them to make and use the full scope of claimed antibodies. 

Taken together, the Amgen and Xencor decisions have significant implications for life sciences and pharmaceutical companies, particularly in the realm of patents involving complex biological inventions. For companies filing patent applications, these rulings underscore the importance of providing a detailed written description and enabling disclosure in such applications, especially when dealing with broad claims involving biological materials like antibodies. 

Furthermore, these rulings emphasize the need for companies to provide clear and specific examples of how the full scope of their inventions can be made and used in practice. This is particularly relevant for pharmaceutical companies developing new treatments, as they must demonstrate not only the theoretical utility of their inventions but also practical applications and potential therapeutic uses, as failure to do so jeopardizes patent protection. 

The Xencor ruling thus adds another layer of patent vulnerability for patent challengers to explore when seeking to invalidate patents covering such complex inventions. Not only should litigators consider whether the patent describes how to actually make and use the full scope of the claims, but also whether the patent is lacking sufficient background information in the written description that is commensurate with the complexity and predictability and known to one of ordinary skill in the relevant art. 

In such a situation, like in Xencor, the patent must include sufficient description to demonstrate that the patentee actually invented the entire breadth of what they’re claiming. If the patent relies on only a few examples attempting to show possession and enablement of a broad, unpredictable area, written description and enablement are good places to look for challenges.  

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