Opinion ID: 4560751
Heading Depth: 2
Heading Rank: 2

Heading: “Antibody Fragment”

Text: The district court construed “antibody fragment” as “a fragment of an antibody which partially or completely lacks the constant region.” The district court further specified that “the term ‘antibody fragment’ excludes bispecific antibodies.” Baxalta, 2018 WL 6304351, at –13. Baxalta argues that the district court’s construction improperly excludes bispecific antibodies and imports limitations from the written description. For reasons related to our construction of “antibody,” we hold that the district court erred in construing “antibody fragment.” We construe that term as “[a] portion of an immunoglobulin molecule having Case: 19-1527 Document: 59 Page: 14 Filed: 08/27/2020 14 BAXALTA INC. v. GENENTECH, INC. a specific amino acid sequence comprising two heavy chains (H chains) and two light chains (L chains).” The district court’s construction relied on the following portion of the written description: The term factor IX/IXa activating antibodies and antibody derivatives may also include . . . e.g., “technically modified antibodies” such as synthetic antibodies, chimeric or humanized antibodies, or mixtures thereof, or antibody fragments which partially or completely lack the constant region, e.g. Fv, Fab., Fab' or F(ab) etc. ’590 patent at 6:15–22 (emphases added). But this excerpt does not, as the district court suggests, define antibody fragments as necessarily “partially or completely lack[ing] the constant region.” Indeed, the standard for lexicography is exacting, requiring the patentee to “‘clearly express an intent’ to redefine a term.” Thorner, 669 F.3d at 1365–66. “[A]lthough the specification often describes very specific embodiments of the invention, we have repeatedly warned against confining the claims to those embodiments.” Phillips, 415 F.3d at 1323. Here, the written description’s use of “may also include,” “e.g.,” “such as,” and “etc.” makes clear the patentee did not intend this excerpt of the written description to define “antibody fragment.” Instead, we construe “fragment” according to its plain and ordinary meaning in light of the written description as a whole. Accordingly, we construe “antibody fragment” to mean “a portion of an antibody” as we have defined above, that is: “a portion of an immunoglobulin molecule having a specific amino acid sequence comprising two heavy chains (H chains) and two light chains (L chains).”