Ajinomoto v. ITC, the Doctrine of Equivalents, and Biomolecule Claim Limitations at the Federal Circuit

Biotechnology Law Report, 2020

25 Pages Posted: 28 May 2020

See all articles by Christopher M. Holman

Christopher M. Holman

University of Missouri - Kansas City School of Law

Date Written: January 1, 2020


The doctrine of equivalents (DOE) allows a court to hold an accused infringer liable for patent infringement in spite of the fact that the accused product (or process) does not fall within the literal scope of the asserted patent claim(s). Prosecution history estoppel (PHE), which can be triggered by a narrowing amendment of a patent claim during patent prosecution, or by arguments made during prosecution, imposes significant constraints on the ability of a patentee to assert the DOE. The 1990s and early 2000’s saw a proliferation of legal commentary postulating that the DOE would play an important role in protecting inventions arising out of biotechnology, particularly biomolecules (i.e., proteins and DNA/polynucleotides), and stressing the need for biotechnology patentees to avoid amendments or arguments during patent prosecution that might trigger PHE. In fact, however, prior to 2019 the Federal Circuit does not appear to have issued an opinion finding infringement under the DOE in a case in which the relevant claim limitation recites a biomolecule. It finally happened in Ajinomoto Co. v. Int'l Trade Comm'n, with a divided panel of the Federal Circuit holding that a claim limitation reciting a DNA sequence, defined in terms of the amino acid sequence of a protein encoded by the sequence, was infringed under the DOE by a DNA sequence encoding a protein having a different (but similar) amino acid sequence and equivalent function. This article begins with a brief overview of the DOE and PHE, and explains why DOE was at one time seen as particularly critical for the enforcement of patent claims reciting biomolecules. It then summarizes and analyzes the results of a Westlaw search designed to identify any and all Federal Circuit decisions applying the DOE and/or PHE to a claim limitation reciting a biomolecule, including the court’s most recent decision Ajinomoto.

Keywords: Ajinomoto, patents, biotechnology, biomolecules, DNA, proteins, doctrine of equivalents, prosecution history estoppel

Suggested Citation

Holman, Christopher M., Ajinomoto v. ITC, the Doctrine of Equivalents, and Biomolecule Claim Limitations at the Federal Circuit (January 1, 2020). Biotechnology Law Report, 2020, Available at SSRN: https://ssrn.com/abstract=3588812

Christopher M. Holman (Contact Author)

University of Missouri - Kansas City School of Law ( email )

5100 Rockhill Road
Kansas City, MO 64110-2499
United States

Do you have a job opening that you would like to promote on SSRN?

Paper statistics

Abstract Views
PlumX Metrics