I, like many other patent prosecutors, have experienced frustration when a patent examiner makes an obviousness rejection under 35 U.S.C. § 103 (or an anticipation rejection under 35 U.S.C. § 102) based on a mischaracterization of what a reference fairly teaches. The height of a patent prosecutor’s angst occurs when the Board of Appeals and Interferences (BPAI) also adopts findings of fact based on such mischaracterizations.
In In re Chapman, the BPAI made not one, but three mischaracterizations of what the primary reference fairly taught. Two of those mischaracterizations on which the BPAI’s obviousness ruling was based were later deemed to be significant by the Federal Circuit. And fortunately for the patent applicant, the Federal Circuit didn’t treat these two significant mischaracterizations as “harmless errors” because “they increase the likelihood that [the patent applicant] was erroneously denied a patent on grounds of obviousness.”
The technology in Chapman relates to “dumbbell-shaped” divalent antibody fragments such as those shown below in Figure 2:
The F(ab’)2 fragment shown in Figure 2 comprises two Fab’ “arms.” Each “arm” comprises one light chain and one heavy chain (each represented as a solid rectangle) which are “linked” by a disulphide bridge (represented as a “-S-S-“ structure) formed by SH groups from the respective cysteine residue of each chain in the “arm.” As indicated in Figure 2, the upper end of each “arm” forms an antigen-binding site, thus making the F(ab’)2 fragment “divalent” because it has two such sites. The lower end of each “arm” (the “hinge region”) are also connected (“linked”) together by a disulphide bridge.
The claimed invention in Chapman was directed to divalent antibody fragments like those shown in Figure 2 but with the light chain (one rectangle) of each “arm” being removed. The remaining heavy chains were also connected together by at least one “intervening” polymer to form at least one nondisulphide “interchain” bridge” between the heavy chains. Also importantly, each end of this “intervening” polymer was covalently bonded to the respective heavy chain at the SH group of a cysteine residue of the heavy chain (e.g., a cysteine residue in the “hinge region”). The alleged benefit for this “intervening” polymer was that it increased the circulating half-life of the antibody fragment for therapeutic purposes.
The patent examiner rejected the claimed invention under 35 U.S.C. § 102(e) as anticipated by U.S. Pat. No. 6, 025, 158 (“Gonzalez”), or alternatively as obvious under 35 U.S.C. § 103(a) over Gonzalez alone, or further in view of U.S. Pat. No. 5,436,154 (“Barbanti”). Like the claimed invention, the primary Gonzalez reference described linking antibody fragments to a polymer to increase an antibody’s circulating half-life for therapeutic purposes. The other relevant teachings of Gonzalez were: (a) a single antibody fragment linked to a polymer(s), including a “dumbbell-shaped” structure made up of two antibody fragments joined by a polymer; (b) identification of six possible choices for the antibody fragment which included the Fab’ antibody fragment; (c) attaching the polymer to a particular amino acid residue or a particular region, including doing so without using a disulphide bond; and (d) a preference for the cysteine residue as an attachment point, particularly a cysteine residue in the “hinge region” of the antibody fragment. (Barbanti was relied upon to describe the use of antibodies for in vivo therapy).
On appeal, the BPAI reversed the patent examiner’s anticipation rejection. But the BPAI also affirmed the patent examiner’s obviousness rejection. The BPAI’s factual findings for affirming the obviousness rejection included the following three statements which became the focal point of the subsequent appeal to the Federal Circuit in Chapman:
1. “[T]he Examiner finds Gonzalez teaches a dumbbell-shaped antibody structure comprised of two monovalent Fab’ fragments (FF 8, 12) and describes linking them via a polymer molecule.”
2. “Gonzalez describes a divalent antibody in which the polymer is linked between light and heavy chains and only one cysteine residue is present (emphasis in the original).”
3. “[t]he antibody can be a monovalent Fab fragment, a monovalent Fab’ fragment which includes one or more cysteine residues in the constant region, or an F(ab’)2 antibody fragment which has a hinge cysteine between the Fab’ fragments.”
In the appeal to the Federal Circuit, the patent applicant initially argued that Gonzalez taught away from two aspects of the claimed invention: (i) using the “hinge” cysteine as an attachment point for the “intervening” polymer; and (ii) using this “intervening” polymer as a bridge between two F(ab’)2 fragments. But this “teaching away” argument didn’t resonate at all with the Federal Circuit.
The patent applicant found a more receptive ear with the Federal Circuit when it argued that the above three BPAI statements were not supported by “substantial evidence.” In fact, the USPTO agreed that these three statements were “erroneous” but were “harmless error.” Like the patent applicant’s initial “teaching away” argument, the USPTO’s assertion of “harmless error” didn’t fly with the Federal Circuit, at least with regard to the BPAI’s second and third statements.
Regarding the BPAI’s first statement, the USPTO agreed that “that Gonzalez does not teach linking “two monovalent Fab’ fragments . . . via a polymer.” The Federal Circuit also agreed with USPTO that the BPAI’s obviousness ruling wasn’t based on this first statement, “but was simply (erroneously) describing a position taken by the examiner.” In fact, as long as the BPAI clarified that it wasn’t relying on this “erroneous” characterization by the patent examiner of what Gonzalez taught, that would have been “harmless error.”
But the Federal Circuit gagged on treating the BPAI’s second and third statements as “harmless error,” as was urged by the USPTO. Regarding the BPAI’s second statement, the USPTO agreed that the patent applicant (not the BPAI) correctly read Gonzalez as teaching that the polymer was attached to either the light or the heavy chain, and thus wasn’t linking the light and heavy chains. That meant that the patent applicant’s “use of a polymer to link together two F(ab’) fragments may be less likely to be obvious.” Regarding the BPAI’s third statement, the USPTO conceded that “Gonzalez teaches six different possible antibody fragments” and thus more than the three antibody fragments suggested by this third statement. That meant that the BPAI “did not appreciate the full scope of antibody fragments disclosed in Gonzalez,” and therefore the Federal Circuit couldn’t “be confident about [the BPAI’s] ultimate conclusion that the selection of one of them to form [the patent applicant’s] molecule is obvious.”
Because the Federal Circuit couldn’t say “with confidence that the [BPAI] would have reached the same conclusion in the absence of these errors, we are persuaded they are indeed harmful.” In other words, this was not a situation where the USPTO’s “path, though convoluted, can be discerned,” citing the 2002 Federal Circuit case of In re Huston.
As observed by the Federal Circuit at the end of Chapman, the BPAI on remand was “in no way precluded from, and indeed may be correct in, finding the claims to be obvious, particularly in the light of Gonzalez’s disclosure of joining two antibody fragments together with a polymer to make a dumbbell-shaped structure.” But what is refreshing and important in the Federal Circuit’s opinion is that mischaracterizations of references relied upon by the patent examiner (or the BPAI) for obviousness rulings are not to be simply glossed over as “harmless error.” Put differently, the Chapman decision gives patent applicant’s a viable legal basis to hold a patent examiner’s (as well as the BPAI’s) “feet to the fire” to challenge an obviousness (or anticipation) rejection based on one or more mischaracterizations of a reference.
*© 2010 Eric W. Guttag.