Recent case law in the United States has changed the landscape for patenting antibodies. In Amgen v Sanofi, 872 F.3d 1367, the Federal Circuit ruled that claiming an antibody by the antigen it binds is insufficient to meet the written description requirement.
Pre-Amgen: claiming “newly characterized” antigens
The written description requirement is set out in 35 U.S. Code § 112(a), which states that a patent must contain a written description of the invention such to enable a person skilled in the art to practice it.
Prior to the Amgen decision, the written description requirement for an antibody could be satisfied by disclosing the structure of a new antigen (or epitope) if the level of skill in the art was such that producing an antibody against such an antigen was conventional or routine at the time. This was known as the “newly characterized antigen test.”
Amgen owned two patents directed to anti-PCSK9 antibodies, which contained claims directed to an genus of antibodies binding specific residues on PCSK9. The patents included claims exemplified by the following claim language:
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
In 2014, Amgen sued Sanofi for infringement. At trial, the District Court instructed the jury that the written description requirement could be satisfied via the newly characterized antigen test. The patents were found valid and infringed, and Amgen was granted a permanent injunction.
Federal Circuit – claiming an antigen is insufficient
The Federal Circuit reversed and remanded for a new trial on written description and enablement, finding that the District Court erred in instructing the jury on written description because “disclosing an antigen does not satisfy the written description requirement for a claim to an antibody.” Specifically, the Federal Circuit said the newly characterized antigen test “flouts basic legal principles of the written description requirement," in that "this test allows patentees to claim antibodies by describing something that is not the invention, i.e., the antigen.”
Moreover, the Federal Circuit held that the District Court’s instruction improperly conflated written description and enablement by allowing the jury to find “the claim was adequately described merely because the antibody could easily be produced”. A new District Court jury trial is scheduled for February 2019 which may provide additional guidance.
In February, the USPTO issued a memo to patent examiners confirming that the newly characterized antigen test should not be used to determine whether there is adequate written description for a claim drawn to an antibody.
Writ of Certiorari
Amgen has filed a certiorari petition at the US Supreme Court asking the Court to consider the question “whether the standard for determining the adequacy of the “written description of the invention” should be as the statute says—that the description must be “in such full, clear, concise, and exact terms as to enable any person skilled in the art to which it pertains . . . to make and use the same” — or whether court-created standards should control instead.” Sanofi filed its reply on November 19th, so the Court should make a decision early in the new year.
Drafting strategy and overcoming rejections
Currently in the US, therapeutic antibodies claimed merely by the antigen to which it binds are not patentable for lack of written description. Instead, patentees are being required to claim features of the antibody itself, such as nucleic or amino acid sequences of CDR sequences or the antibodies themselves.
Pending applications that claim an antibody by its cognate antigen should be reviewed and claims amended to include structural features of the antibody.