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."
