Pharmaceutical Composition Claim Infringed By Structural Analog Equivalent

In Abraxis Bioscience, Inc. v. Mayne Pharma , (No. 06-1118; November 15, 2006), a Federal Circuit panel reverses a district court's finding of literal infringement and upholds a finding of infringement under the doctrine of equivalents. The infringement analysis focuses on the construction of the word “edetate” which was defined in the specification as “EDTA and derivatives thereof.” The panel determines that the term “derivatives” is defined by the rest of the specification to include the salts, but not structural analogs, of EDTA.

Abraxis conceded that the compound used by Mayne, DTPA, is only a structural analog of EDTA. Accordingly, based on the narrower claim construction, the panel finds no literal infringement. However, the panel determines that DTPA meets the Graver Tank function-way-result test and is an equivalent of EDTA. In particular, the Court states both edetate and DTPA retard microbial growth by metal ion chelation to achieve microbial growth retardation. Rejecting Mayne's argument that Abraxis is barred from this equivalent, the Court holds that Abraxis did not make a clear and unmistakable surrender of subject matter as necessary to disavow DTPA as an equivalent by argument during prosecution. The Federal Circuit panel also notes that the District Court findings that DTPA was selected by Mayne because of its structural similarities to edetate and the likelihood that it would match the product characteristics and stability profile of Abraxis' formulation are consistent with the determination that DTPA and EDTA perform substantially the same function in substantially the same way to obtain the same result.