Today in Biogen Idec v. GlaxoSmithKline a divided panel of the Federal Circuit affirmed a district court’s decision that GSK's monoclonal antibody product Arzerra does not infringe Biogen's patent number 7,682,612. I discussed the district court's decision in an October 2011 blog post. Arzerra is a fully human antibody that specifically binds to a small loop on the CD20 antigen. Biogen markets a competing product, Rituxan, which is a chimeric antibody that targets a different, larger loop on the CD20 antigen.
Representative claim 1 of Biogen's patent 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.
The dispute centered on the interpretation of the claim term "anti-CD20 antibody." The District Court construed the term as limited to antibodies that bind to the same epitope of the CD20 antigen as Rituxan, i.e., the large loop. Under this interpretation, Biogen stipulated to noninfringement, since it is undisputed that Arzerra binds to a different epitope, i.e., the small loop.
On appeal, the Federal Circuit majority affirmed the district court's claim interpretation, based on the doctrine of "prosecution history disclaimer." The majority noted that while claim terms are generally given their ordinary and customary meaning, a "clear and unmistakable" disavowal of subject matter during prosecution overcomes the "heavy presumption" that claim terms carry their full ordinary and customary meaning. In this case, although the ordinary meaning of anti-CD20 antibody would presumably encompass any antibody that specifically recognizes any epitope on the CD20 antigen, the majority found that statements made during prosecution limited the claim to antibodies that bind at the same epitope as Rituxan. The majority pointed out that when representations are made by the time the during prosecution, "competitors are entitled to rely on those representations when determining a course of lawful conduct, such as launching a new product or designing-around a patented invention."
To summarize, during prosecution the examiner rejected Biogen’s claims for lack of enablement, finding that while the specification was enabling for Rituxan, but that it was "silent concerning what sort of specificity and affinity would be necessary" for other anti-CD20 antibodies. In response, Biogen pointed to its disclosure of Rituxan and argued 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.
After considering this argument, the examiner withdrew the enablement rejection. Even though the claims were not amended, the majority found that by arguing that the specification was enabling for antibodies with similar affinity and specificity as Rituxan, instead of challenging the examiner's understanding of the crucial terms, Biogen had effectively limited its claims to antibodies similar to Rituxan, i.e., antibodies binding the same epitope.
A dissenting opinion was filed by Judge Plager, who found that Biogen's arguments during prosecution were sufficiently ambiguous that they did not meet the "clear and unmistakable" disclaimer standard necessary to overcome the presumption that claim terms should be attributed their plain meaning. He voiced the opinion that Biogen's argument represented nothing more than "the give-and-take that is often part of the process of negotiation between it and examiner and an applicant [which] may result in less-than-clear understandings,” and that the majority had made "too much of such ambiguous statements."