Federal Circuit Finds Prosecution History Disclaimer in Enablement Arguments

23 April 2013 PharmaPatents Blog

In Biogen Idec, Inc. v. GlaxoSmithKline LLC, the Federal Circuit upheld a narrow claim interpretation based on prosecution history disclaimer. The court held that the applicants’ arguments against an enablement rejection served to disclaim the broader claim scope sought in the infringement action. This case highlights the risk that any statement made during prosecution can be used to construe the scope of the claims.

The Patent at Issue

The patent at issue is Biogen’s U.S. Patent 7,682,612, directed to “Treatment of Hematologic Malignancies Associated with Circulating Tumor Cells using Chimeric Anti-CD20 Antibody.” Claim 1 recites:

1. A method of treating chronic lymphocytic leukemia in a human patient, comprising administering an anti-CD20 antibody to the patient in an amount effective to treat the chronic lymphocytic leukemia, wherein the method does not include treatment with a radiolabeled anti-CD20 antibody.

Chronic lymphocytic leukemia (CLL) is marked by overproduction of malignant B-cells. The anti-CD20 antibody binds to CD20, a protein on the surface of B-cells, targeting the cells for destruction. The specification describes Biogen’s product Rituxan® (rituximab) as a preferred embodiment. Rituximab binds to a large loop of the CD20 protein that is exposed on the cell surface. This loop constitutes the particular “epitope” recognized by the rituximab antibody.

The District Court Proceedings

Biogen sued GSK for infringement of the ‘612 patent by GSK’s anti-CD20 antibody Arzerra® (ofatumumab). Arzerra® binds to a smaller  loop of the CD20 protein than rituximab. (At the time the ‘612 patent application was filed, it was believed that the loop (epitope) recognized by Arzerra® was hidden inside the cell, and thus unavailable for binding by antibodies.) Arzerra® binds to CD20 with higher affinity than Rituxan®, making it more effective in destroying B cells.

One of the claim construction issues decided by the district court was whether the “anti-CD20 antibody” recited in the claims encompasses antibodies that bind to any CD20 epitope, or only antibodies that bind to the epitope bound by rituximab.  The court adopted the narrow construction based on prosecution history disclaimer. In particular, the court determined that Biogen had limited the scope of the claims by arguments presented to overcome an enablement rejection. Because GSK’s antibody binds to a different epitope than rituximab, the district court found that there was no infringement.

The Enablement Rejection

The USPTO Examiner made the following enablement rejection:

Claims 1 and 12 are broadly drawn to ‘. . . an anti-CD20 antibody or fragment thereof’. This is broadly interpreted for examination purposes to be any and all anti-CD20 antibodies, no matter the specificity or affinity for the specific epitope on the circulating tumor cells. While the specification is enabling for the application of RITUXAN®, RITUXIMAB® and 2B8-MX-DTPA in the treatment of hematologic malignancies, the specification is not enabling in the application of all other anti-CD20 antibodies, which may have different structural and functional properties.

(February 29, 2000 Non-Final Rejection, page 6.)

In response, the applicants argued:

Applicants respectfully submit that even though antibodies directed to the same antigen might have different affinities and functional characteristics, one of skill in the art could readily identify an antibody that binds to CD20 with similar affinity and specificity as does RITUXAN® using techniques that are well known in the art. . . . With that knowledge in hand, the skilled artisan could readily produce anti-CD20 antibodies using similar techniques, and screen such antibodies for those having an affinity and functional activity similar to Rituxan®.

(August 29, 2000 Reply, pages 8-9.)

The USPTO Examiner accepted these arguments and withdrew the enablement rejection.

The Federal Circuit Decision

Judge Reyna authored the Federal Circuit decision, which was joined by Judge Dyk. Judge Plager dissented, as discussed below.

The Federal Circuit agreed with the district court’s finding of prosecution history disclaimer.  In discussing this doctrine, the Federal Circuit  noted that “a ‘clear and unmistakable’ disavowal during prosecution overcomes the ‘heavy presumption’ that claim terms carry their full ordinary and customary meaning,” quoting from its 2003 decision in Omega Engineering, Inc. v. Raytek Corp.

[W]hen the patentee unequivocally and unambiguously disavows a certain meaning to obtain a patent, the doctrine of prosecution history disclaimer narrows the meaning of the claim consistent with the scope of the claim surrendered.

The Federal Circuit framed the issue as follows:

This case requires us to analyze how the PTO and the inventors understood the disputed term, “anti-CD20 antibody,” in the ’612 patent to determine if the inventors disclaimed claim scope during prosecution of that patent. Biogen maintains that all the evidence—including the claims, the specification, and statements made by all parties recorded in the prosecution history—indicates that the term was used according to its plain and ordinary meaning, “an antibody that binds to a cell surface CD20 antigen.” ….  The question becomes whether statements in the prosecution history are sufficient to overcome the “heavy presumption” that the term carries its full ordinary and customary meaning advanced by Biogen.

The Federal Circuit inferred the USPTO Examiner’s understanding of the claim term from the enablement rejection:

During prosecution of the ’612 patent, the examiner rejected all pending claims because the specification did not enable a person skilled in the art to practice the full scope of the claims, which could have encompassed “any and all anti-CD20 antibodies, no matter the specificity or affinity for the specific epitope on the circulating tumor cells.” …. Instead, according to the examiner, the specification only enabled Rituxan®, rituximab, and 2B8-MX-DTPA.4 It was not enabling for other antiCD20 antibodies, which had different structural and functional properties.

(Doesn’t this rejection indicate that the USPTO Examiner had interpreted the claims broadly?)

The Federal Circuit found that disclaimer arose from the applicants’ response:

In response, rather than challenging the examiner’s understanding of the crucial terms, the applicants argued that the specification was enabling for anti-CD20 antibodies with similar affinity and specificity as Rituxan®.

The court interpreted the applicants’ arguments as “conced[ing] that other ‘antibodies directed to the same antigen [i.e., CD20] might have different affinities and functional characteristics,’” and “limit[ing] their claims to antibodies similar to Rituxan® nonetheless.”

[I]t is clear that they were limiting their invention to what the examiner believed they enabled: antibodies that have a similar specificity and affinity for the specific epitope to which Rituxan® binds.

(But the Examiner allowed the claims with the language he had interpreted broadly … )

Biogen argued that the fact that dependent claims are specifically directed to rituximab supports a broader construction of the independent claim, but the court rejected this argument, stating that prosecution history disclaimer can overcome any presumption arising from claim differentiation.

The Federal Circuit therefore upheld the district court’s claim construction and finding of non-infringement.

Judge Plager’s Dissent

Judge Plager dissented, because he found no “clear and unmistakable evidence of disclaimer.” Judge Plager criticized the majority for “teas[ing] out” disclaimer from the prosecution history, and for keying disclaimer to statements made by the USPTO Examiner, not the applicants:

Applicants’ statements—when considered in light of either the range of antibodies included in the claim, or the specific epitope to which the antibodies might attach—fail to meet the “clear and unmistakable” standard set forth in our case law. This is especially true given our case law that it is the applicant, not the examiner, who disclaims claim scope. …. It was the examiner, not the applicants, who invoked the concept of epitopes. …  But it is the applicant, not the examiner, who must give up or disclaim subject matter that would otherwise fall within the scope of the claims, and an applicant’s silence regarding statements made by the examiner during prosecution cannot amount to a clear and unmistakable disavowal of claim scope.

Judge Plager emphasized that the applicants’ response did not refer to a particular epitope, but simply stated that “one of skill in the art could readily identify an antibody that binds to CD20 with similar specificity and affinity.” Judge Plager noted that when an argument is subject to more than one reasonable interpretation, it cannot rise to the level of a clear and unmistakable disclaimer.

A Miranda Warning? 

The decision here brings to mind the Miranda warning: anything you say during prosecution can and will be used against you during a claim construction proceeding.

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