Post-Priority-Date Evidence Admissible To Challenge Written Description

  • April 29, 2020
Amgen, Inc. v. Sanofi, Aventisub LLC

In Amgen, the Federal Circuit held that an accused infringer may rely on evidence dated after the priority date of the patent to allege that the patentee failed to satisfy the written description requirement of the Patent Act.

Amgen is the owner of two patents directed to antibodies useful in reducing LDL, or “bad” cholesterol. Amgen sued a collection of pharmaceutical companies, including Sanofi, alleging the Sanofi’s antibody-based cholesterol treatment infringed the patents. Sanofi defended that Amgen’s patents failed to satisfy the written description requirement of the Patent Act, because the examples in the patent were not sufficient to disclose the structural features common to members of the claimed genus.

The district court refused to admit Sanofi’s written description evidence because it post-dated the earliest priority date to which the claims of the patents were entitled. The district court also instructed the jury that the written description requirement could be satisfied if the patent disclosed a newly characterized antigen, and if the level of ordinary skill in the art at the time was sufficient that producing antibodies against such an antigen was conventional and routine. The jury determined that the patents satisfied the written description requirement and were infringed by Sanofi. Sanofi appealed.

The written description requirement is set out in Section 112 of the Patent Act. A patent must contain a written description of the invention sufficient to show that the inventor actually invented what is claimed, and had possession of the claimed subject matter on the filing date.

The Federal Circuit reversed the district court’s refusal to admit post-priority-date evidence challenging the patents’ written description. Evidence produced after the priority date for a patent-in-suit is generally not admissible to teach the state of the art at the time the patent was filed. However, such evidence may be used for another purpose, including to show that the species disclosed in a patent were not representative of the entire genus covered by the claims. Sanofi should have been permitted to introduce evidence that other antibodies, including its own later-produced antibodies, differed considerably from the antibodies disclosed in the patent.

The Federal Circuit also rejected the district court’s jury construction. In some cases, a description of functional characteristics of an invention combined with a known correlation between function and structure may satisfy the written description requirement. But such a conclusion in this case requires proof that making and using the claimed antibodies was so routine that possessing the antigen was equivalent to possessing the genus of antibodies. No such proof existed.

Key Takeaway

Post-priority date evidence may be admissible to show that the patentee did not have possession of the full scope of the claimed invention at the time the patent was filed. Additionally, the patentee may not satisfy the written description requirement on a claim to an antibody, by fully characterizing an antigen and arguing that production of antibodies from such an antigen was conventional and routine.


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