The Federal Circuit recently vacated a District Court decision by Federal Circuit Judge Dyk, sitting by designation, based on erroneous claim construction in Baxalta Inc. v. Genentech, Inc.
The case arose over Genentech's Hemlibra® (emicizumb-kxwh) product, which Baxalta alleged infringed its U.S. Patent No. 7,033,590. Baxalta asserted claims 1, 4, 17, and 19; these claims were directed to certain elements of the "blood clotting cascade" for treatment of hemophilia A. The invention claimed in the '590 patent involved using antibodies or antibody fragments to replace binding of Factor VIII (which is deficient or inhibited in hemophiliacs) to Factor IX, which permits restoration of the cascade (wherein Factor IX activates Factor X) as set forth in the following drawing:
The Federal Circuit found Claims 1, 4, and 19 to be illustrative:
1. An isolated antibody or antibody fragment thereof that binds Factor IX or Factor IXa and increases the procoagulant activity of Factor IXa.
4. The antibody or antibody fragment according to claim 1, wherein said antibody or antibody fragment is selected from the group consisting of a monoclonal antibody, a chimeric antibody, a humanized antibody, a single chain antibody, a bispecific antibody, a diabody, and di-, oligo- or multimers thereof.
19. The antibody or antibody fragment according to claim 4, wherein the antibody is a humanized antibody.
At trial, the parties proposed alternative claim constructions for the terms "antibody" and "antibody fragment." Baxalta's proposed claim construction defined "antibody" as "[a] molecule having a specific amino acid sequence comprising two heavy chains (H chains) and two light chains (L chains)." Genentech's proposed construction was that "antibody" should be construed as "[a]n immunoglobulin molecule, having a specific amino acid sequence that only binds to the antigen that induced its synthesis or very similar antigens, consisting of two identical heavy chains (H chains) and two identical light chains (L chains)" (emphasis added). These differences were relevant because Genentech's Hemlibra® product was a bispecific antibody, i.e., the heavy and/or light chains comprising the antibody were different, thus permitting the two portions of the antibody to recognize and bind to different antigens. Judge Dyk, sitting by designation, held that the term "antibody," without more, could have different meanings to the skilled worker and both parties' definitions were consistent with these different meanings. In deciding to adopt Genentech's proposed construction, Judge Dyk held that Baxalta's specification contained a definition of the term that was dispositive:
Antibodies are immunoglobulin molecules having a specific amino acid sequence which only bind to antigens that induce their synthesis (or its immunogen, respectively) or to antigens (or immunogens) which are very similar to the former. Each immunoglobulin molecule consists of two types of polypeptide chains. Each molecule consists of large, identical heavy chains (H chains) and two light, also identical chains (L chains).
This definition was inconsistent with the remainder of the '590 specification, that disclosed bispecific antibodies, and also inconsistent with other naturally occurring...
