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Listing of Salts in Specification Limits the Term "Derivatives" to Salts

November 15, 2006

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Last Month at the Federal Circuit - December 2006

Judges: Lourie (author), Plager, Rader

[Appealed from: S.D.N.Y., Judge Pauley]

In Abraxis Bioscience, Inc. v. Mayne Pharma (USA) Inc., No. 06-1118 (Fed. Cir. Nov. 15, 2006), the Federal Circuit reversed the district court’s finding of literal infringement but affirmed the district court’s finding of infringement under DOE.

Mayne Pharma (USA) Inc. (“Mayne”) attempted to design around a patent for a pharmaceutical composition used to induce and maintain general anesthesia and sedation in patients, which was owned by Abraxis Bioscience, Inc. (“Abraxis”). During the design-around, Mayne attempted to match the characteristics and stability function of disodium edetate, ethylenediaminetetraacetic acid (“EDTA”), a preservative in the patented formulation. They eventually chose the calcium trisodium salt of diethylenetriaminepentaacetic acid (pentetate) (“DTPA”) as a replacement because it was “structurally similar to edetate, [and therefore] product stability is predicted to be unaffected.” Slip op. at 4.

Mayne filed an ANDA on its generic formulation and included a paragraph IV certification that Abraxis’s patents were invalid, unenforceable, and would not be infringed by its generic formulation. Abraxis filed suit. The district court issued a Markman ruling, construing three contested claim terms, including the term “edetate,” which was at issue on appeal. The district court adopted an interpretation of “edetate” that included “EDTA as well as compounds structurally related to EDTA regardless of how they are synthesized.” Id. at 5. Based on this construction, the district court found that Mayne’s product infringed, both directly and under the DOE, after a bench trial.

On appeal, the Federal Circuit agreed with the district court’s finding that “edetate” includes “EDTA and derivatives of EDTA,” as the term is defined in the specification, but rejected the district court’s definition of “derivatives.” Under the district court’s construction, the term “edetate” encompassed  not only salts of EDTA but also structural analogs (a relatively voluminous category of structurally similar chemical compounds, some of which are only tangentially related to EDTA). The Federal Circuit, following the principles set forth in Phillips, however, relied on evidence from the claim language itself and the specification to reject the inclusion of the structural analogs. The Court noted that the specification lists only EDTA and specific salts of EDTA, none of which are structural analogs. Additionally, the specification discloses that considerable effort was spent experimenting with preservatives and eventually narrowing down to one specific agent, edetate. Thus, the Federal Circuit concluded that the term “edetate” includes EDTA and derivatives of EDTA, such as salts, but not structural analogs.

Because Abraxis conceded during oral argument that DTPA is not a derivative of EDTA because it cannot be synthesized from EDTA in a laboratory and it is not a salt of EDTA, the Federal Circuit reversed the district court’s finding of literal infringement.

The Federal Circuit then went on to analyze infringement under the DOE and agreed with the district court’s conclusion that calcium trisodium DTPA and edetate were equivalent because their differences were insubstantial. In reaching its conclusion, the district court performed the functionway- result test. In reviewing the district court’s analysis, the Federal Circuit first held that the district court “properly assessed the ‘way’ edetate works by referring to the patent and the evidence presented at trial,” which supported the conclusion that DTPA and EDTA both perform as an antimicrobial agent by metal ion chelation. Id. at 16.

Second, the Federal Circuit held that it was permissible for equivalents to extend beyond EDTA because “the inventors did not clearly disavow other polyaminocarboxylates, including DTPA, by claiming edetate. There is no evidence that the patentees made a clear and unmistakable surrender of other polyaminocarboxylates, or calcium trisodium DTPA in particular, during prosecution.” Id. at 18.

Finally, the Federal Circuit noted that “known interchangeability is only one factor to consider in a doctrine of equivalents analysis,” and rejected Mayne’s argument that the lack of known interchangeability between edetate and DTPA as an antimicrobial agent necessitated the conclusion that the accused product does not infringe under the DOE. Id. at 19. The district court made factual findings that insubstantial differences exist between calcium trisodium DTPA and edetate, notwithstanding Mayne’s own patent covering the DTPA compound.

Thus, while reversing the district court’s claim construction and finding of literal infringement, the Federal Circuit affirmed the district court’s analysis of infringement under the DOE.