13Sep 2019
Blog article by Silvia Salvadori - Infringement Under the Doctrine of Equivalents: 2 Cases Examined

In two recent cases, the Federal Circuits held that claim amendments at issue were “tangential” to the “equivalent” at issue, and upheld findings of infringement.

The case details are below: 

Case #1: Ajinomoto Co. v. ITC 

The claim amendment at issue related to an encoding nucleotide sequence. The original claim language recited “a protein which comprises an amino acid sequence including deletion, substitution, insertion or addition of one or several amino acids in the amino acid sequence shown in SEQ ID NO:2,” and was replaced with “a protein which comprises an amino acid sequence that is encoded by a nucleotide sequence that hybridizes with the nucleotide sequence of SEQ ID NO:1 under stringent conditions.”

The Federal Circuit agreed with ITC’s determination that the amendment was “tangential” to the equivalent at issue based on the following:

  • The rationale for the amendment was to limit the set of proteins claimed so that it no longer included a protein found in the prior art and was not related with choosing among several DNA sequences in the redundant genetic code that correspond to the same protein.

Thus, according to the Federal Circuit, prosecution history estoppel did not bar application of the doctrine of equivalents.

Case #2: Eli Lilly and Co. v. Hospira, Inc.

During prosecution, the language of administering “pemetrexed sodium” was amended to administering “an antifolate” to distinguish the claims from a prior art reference.

The accused products contained pemetrexed ditremethamine, not pemetrexed sodium, but the Federal Circuit found that the amendment was “tangential” to the equivalent, and thus prosecution history estoppel did not apply.  

The amendment was not related to the type of salt, thus, the applicant did not surrender other pemetrexed salts.

Final Thoughts

Even if within these cases it was possible to find infringement under the doctrine of equivalents, it should be kept in mind that where the reason for the amendment and the equivalent in question both relate to the same claim element, the tangential exception does not apply.

Please contact me at silvia@salvadorilaw.com with questions or comments.

Silvia Salvadori, PhD

Silvia Salvadori, PhD