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Claims for Detecting and Localizing a Tumor May Be Infringed Under DOE

June 23, 2004

Decision icon Decision

Last Month at the Federal Circuit - June/July 2004

Judges: Gajarsa (author), Schall, and Prost (concurring-in-part and dissenting-in-part)

In Goldenberg v. Cytogen, Inc., No. 03-1409 (Fed. Cir. June 23, 2004), the Federal Circuit affirmed the district court’s grant of SJ that Cytogen, Inc.’s (“Cytogen”) ProstaScint, a prostate-specific membrane antigen (PSMA) marker, did not literally infringe U.S. Patent No. 4,460,559 (“the ’559 patent”), but reversed the district court’s finding of infringement of the ’559 patent under the DOE and remanded for further proceedings.

The ’559 patent is directed to a method for detecting and localizing tumors by targeting “intracellular marker substances” that are produced by or associated with tumor cells. The claimed method includes injecting a subject with a radioactively highlighted antibody specific to the “marking substance,” which, when scanned, reveals the location of concentrations of the “marking substance” within the body.

Milton D. Goldenberg and Immunomedics, Inc. (collectively “Immunomedics”) filed suit against Cytogen and C.R. Bard, Inc. (collectively “Cytogen”), alleging that because PSMA is an “intracellular marker substance” and the antibody in Cytogen’s ProstaScint targets PSMA, then ProstaScint infringes the method claims of the ’559 patent. Specifically, Immunomedics alleged that ProstaScint infringed the method claims of the ’559 patent by containing the antibody 7E11-C5.3 (an antibody specific to PSMA).

The method of claim 1 in the ’559 patent included the term “intracellular marker substance.” Immunomedics failed to define in the specification the term “intracellular marker substance,” and theparties agreed that the term had no commonly accepted meaning. In construing the term, the district court reviewed the intrinsic evidence and considered expert testimony. The district court construed “intracellular marker substance” to mean “an antigen existing within a body cell.” Both parties filed motions for SJ based on the claim construction. The district court, concluding that PSMA was a cell-surface antigen, granted Cytogen’s motions for SJ of noninfringement.

The ’559 patent was one of two patents that originated from two simultaneously filed applications. A continuation of the first application resulted in the ’559 patent, and a CIP of the second application resulted in U.S. Patent No. 4,444,744 (“the ’744 patent”). In its literal infringement analysis, the district court relied on passages added during the prosecution of the ’744 patent where Goldenberg distinguished the parent application of the ’744 patent from the ‘559 patent to overcome a double-patenting rejection during prosecution of the ’559 patent. The district court consequently relied on both the definition and the references in the ’744 patent to conclude that PSMA was a cellsurface antigen and was therefore outside of the literal scope of claim 1.

The Federal Circuit reviewed the claim construction of the term “intracellular marker substance” and affirmed the district court’s construction. The Federal Circuit also agreed with the district court’s finding that the marker substance must be wholly internal to the cell. The Federal Circuit stated, however, that the relevant passages from the ’744 patent relied on by the district court constituted new matter added by the CIP; thus, it does not constitute part of the prosecution history of the ’559 patent. Nevertheless, the Federal Circuit reached the same construction based on the intrinsic evidence of the ’559 patent and held that the district court’s use of the passages from the ’744 patent was harmless error.

In affirming the district court’s construction of the term “intracellular marker substance,” the Federal Circuit agreed that, as a transmembrane antigen, PSMA is not an intracellular marker substance. As to the DOE, however, the Federal Circuit held that the district court improperly relied on the faulty premise of classifying PSMA as solely a cell-surface antigen.

Additionally, the Federal Circuit found that Immunomedics had presented a sufficient factual dispute to avoid SJ. The Court noted that transmembrane antigens are not susceptible to the black and white categorization made by the district court, and “[a]s a ‘grey’ category, transmembrane antigens are not addressed by the ’559 patent or its prosecution history and might be equivalent to either of the categories [cell-surface marker or intracellular marker] identified by the district court if such a finding was made.” Slip op. at 17.

Accordingly, the Federal Circuit found that Immunomedics had presented a sufficient factual dispute to avoid SJ and remanded to the district court for further proceedings on the issue of infringement under the DOE.