Written Description Requirement for Antibody Claims

The Federal Circuit reversed and remanded a decision by the Delaware district court that found claims directed to a genus of antibodies satisfied the written description and enablement requirements.¹ The Federal Circuit held that the district court erred by (1) excluding post-priority-date evidence to demonstrate that the patents did not provide adequate written description and (2) improperly instructing the jury on written description.²

The patents relate to antibodies that reduce low-density lipoprotein cholesterol (LDL-C) by blocking the binding of PCSK9 to LDL-R. Claim 1 of U.S. Patent No. 8,829,165 is representative:

An isolated monoclonal antibody, wherein, when bound to PCSK9, the monoclonal antibody binds to at least one of the following residues: S153, I154, P155, R194, D238, A239, I369, S372, D374, C375, T377, C378, F379, V380, or S381 of SEQ ID NO:3, and wherein the monoclonal antibody blocks binding of PCSK9 to LDL-R.³

Post-priority-date evidence

Sanofi, the patent challenger, argued that the claims lacked written description because the patent specification did not disclose a representative number of species of the claimed genus. Sanofi asserted that evidence of species that fall within the claimed genus, but which are not disclosed by the patent, can include post-priority date evidence.⁴

Amgen argued that written description is determined based on the state of the art as of the priority date, such that evidence illuminating the state of the art after the priority date is irrelevant to written description⁵ (citing Ariad Pharm., Inc. v. Eli Lilly & Co).⁶

The Federal Circuit found that it is proper to use post-priority date evidence to show that a patent does not disclose a representative number of species of a claimed genus⁷ because the evidence was introduced “not to illuminate the state of the art on the priority date but to show that the patent purportedly did not disclose a representative number of species.”⁸ The Federal Circuit therefore reversed and remanded the district court’s decision to exclude post-priority-date evidence.

Jury Instructions

The second issue remanded to the district court relates to whether “the correlation between structure and function [for a claim to antibodies] may be satisfied by the disclosure of a newly characterized antigen.”⁹

The district court instructed the jury that the written description requirement can be satisfied “by the disclosure of a newly-characterized antigen… if you find that the level of skill and knowledge in the art of antibodies at the time of filing was such that production of antibodies against such an antigen was conventional or routine.”¹⁰

The Federal Circuit found these instructions improper because they “effectively permitted the jury to dispense with the required finding of a ‘written description of the invention’.” ¹¹

[T]o satisfy the statutory requirement of a description of the invention, it is not enough for the specification to show how to make and use the invention, i.e., to enable it. Yet the instruction in this case invites just that improper equation. A jury would naturally understand the instruction to permit it to deem any antibody within the claim adequately described merely because the antibody could easily be produced. [citations omitted¹²

Furthermore, the Federal Circuit found that

[T]he ‘newly characterized antigen’ test flouts basic legal principles of the written description requirement. Section 112 requires a ‘written description of the invention.’ But this test allows patentees to claim antibodies by describing something that is not the invention, i.e., the antigen. ¹³

The Federal Circuit therefore found the jury instructions improper and remanded the case to the district court to amend its jury instructions.