Patentee Burden Drives PTAB Obviousness Analysis

In Prolitec, Inc., v. Scentair Technologies, Inc.  the Court of Appeals for the Federal Circuit (CAFC) confirmed that patentees bear the burden of demonstrating patentability for amended claims in AIA trial proceedings before the USPTO Patent Trial & Appeal Board (PTAB).  Prolitec also found that this burden encompassed both the art of record in the AIA trial proceeding as well as the original patent prosecution history.

Earlier this week, in Illumina Cambridge LTD., v. Intelligent Bio-Systems, Inc., the Court explored the PTAB's analysis of amended claims relative to the burden of the patentee.  That is, whether or not the Board is required to do a traditional obvious analysis for amended claims, anew, or whether the existing record can be used as a backdrop by which the movant's burden can be assessed.

The patents at issue in the appeal are 7,057,026 and 8,158,346, both relating to DNA sequencing by synthesis (“SBS”) with non-natural nucleotides. SBS allows one to determine the composition of a target DNA sequence by synthesizing new copies of the DNA.  In amending its claims, Illumina added the limitation that the cleavable linker “contains a disulfide linkage.”  The Board denied the amended claims as unpatentable.

On appeal, Illumina argued that the Board, focused on the added limitation to the exclusion of the rest of the claim.  Illumina reasoned that because the prior art teaches both that SBS requires greater than 90% deblocking efficiency, and that cleaving disulfide linkages was variable and inefficient, one of skill in the art would not have been motivated to combine the prior art for SBS methods. In the view of Illumina, the presence of a disulfide linkage in the art was not enough absent the view of the combination.

For its part, Intelligent Bio-Systems ("Bio") responded [to Illumina’s argument that “the Board improperly limited its analysis to the disulfide linkage limitation, rather than also considering the combination of the additional limitations] that Illumina failed to carry its burden of showing that the proposed substitute claims were patentable over the prior art of record.  Bio also argued that because the Board had already decided in it Decisions to Institute that the prior art taught all of the limitations in the original claims, the only additional limitation in the proposed claims was the disulfide linker, and thus the Board only needed to address the prior art relating to the successful use of disulfide linker in DNA sequencing.

(Of course, a Decision to Institute is preliminary. Yet, amendment is only denied at the time of Final Written Decision (FWD).  Here, the Board seemingly had not strayed from its original determination.)

In affirming the Board, the Court explained (here):

Because none of the original claims comprised the limitation of the linker containing a disulfide linkage, the Board chose to primarily address prior art relevant to that limitation to determine whether Illumina had proven that the addition rendered the claims as a whole nonobvious.

The Board did not analyze the obviousness of using a disulfide linkage in SBS in isolation, however; the original claims provided a backdrop for the Board to find that one of skill in the art would have reasonably expected to succeed in using a linker with a disulfide linkage as claimed. The prior art taught the use of linkers containing disulfide linkages for attaching a label to a nucleotide, as well as the desirability of simultaneously removing labels and protecting groups, in DNA sequencing methods. One of skill in the art would have been motivated to use a commercially available linker to attach a label to a nucleotide that also could be removed when removing the protecting group, and thus would have been motivated to modify SBS prior art with a disulfide linkage as claimed. The heightened standard that Illumina decries is instead properly Illumina’s burden to show nonobviousness, proof that one of skill in the art would not have a reasonable expectation of success in using a disulfide linkage

(emphasis added)

Stated another way, it was not the Board's burden to demonstrate obviousness in a traditional sense (by assessing the claim as a whole). Rather, the Board may simply fault the patentee's showing, focusing on the newly added language as compared to the existing record, which was reaffirmed by the Board at the time of the FWD.