Structurally Similar Compound Did Not Literally Infringe, But Infringed Under the Doctrine of Equivalents

Case: Abraxis Bioscience, Inc. v. Mayne Pharma (USA) Inc., No. 06-1118 (Fed. Cir. 11/15/06)

The One Sentence Summary: A structurally similar preservative compound did not infringe literally, but did infringe under the doctrine of equivalents.


What They Were Fighting About: Abraxis sued under Mayne under patents on the use of edetate as a preservative in an anesthetic. The district court found that defendants' use of a structurally analogous compound infringed literally and under the doctrine of equivalents.

Federal Circuit Holdings:

• The district court erred in construing the term "edetate" in the claim language to include structural analogs of EDTA. Although the patentee acted as its own lexicographer in defining the term "edetate" to mean "EDTA and its derivatives", the specification did not include structural analogs as examples of "derivatives."
• Due to its error in construing the scope of the claims, the district court erred in finding literal infringement.
• However, the district court correctly found infringement under the doctrine of equivalents. After trial, the district court found that the compound in defendant's preservative performed the same function in the same way with the same result.
• Both patentee's compound and defendant's compound worked in the same "way", through metal ion chelation, and the panel rejected defendant's argument that the specific types of chemical bonds needed to be analyzed.
• Even though patentee described its compound as "edetate" rather than the broader category of "polyaminocarboxylates", it was not estopped from claiming infringement under the doctrine of equivalents because it did not make a clear and unmistakable surrender of the equivalents.
• The lack of known interchangeability between the compounds used by patentee and defendant did not prevent a finding of infringement under the doctrine of equivalents. The district court did not err in finding that there were insubstantial differences in the compounds, and that defendant had chosen its compound because of its similar structure and reactivity to the compound used in the patents.