Praxair filed a first petition for inter partes review of claims 1-19 of U.S. Patent 8,846,112.  The PTAB instituted review based on the first petition and concluded that all claims, except claim 9, were unpatentable.  In doing so, the PTAB determined that the “providing information” step in claim 1, and “similarly-worded claims steps in other claims, constituted printed matter and, therefore, accorded the term no patentable weight with respect to claims 1-8 and 10-19.”  Praxair Distribution, Inc. v. iNO Therapeutics LLC, IPR2016-00781, Paper 10, slip op. at 6 (Aug. 25, 2016) (discussing its earlier decision in Praxair Distribution v. Malllinckrodt Hospital Prods. IP Ltd., IPR2015-00529, Paper 53, slip op. at 15-21 (July 7, 2016)).

Apparently concerned the Federal Circuit might not agree with the PTAB regarding its “no patentable weight” determination and reverse the PTAB, Praxair filed a second petition with two new textbook references that allegedly disclosed the “providing information” limitation.  Id.  In its Preliminary Response, the Patent Owner argued that Praxair was estopped from requesting or maintaining the IPR under § 315(e)(1) and, further that the PTAB should exercise its discretion to deny the second Petition under § 325(d).  The PTAB agreed with both arguments.  Id. at 2.

The PTAB began its analysis of the estoppel issue by turning to the language in 35 U.S.C. § 315(e)(1):

The petitioner in an inter partes review of a claim in a patent … that results in a final written decision under section 318(a) … may not request or maintain a proceeding before the Office with respect to that claim on any ground that the petitioner raised or reasonably could have raised during that inter partes review [emphasis added].

The PTAB then turned to the legislative history of the AIA for a description of grounds that “reasonably could have been raised” and determined that it “encompass[ed] ‘prior art which a skilled searcher conducting a diligent search reasonably could have been expected to discover.’  157 Cong. Rec. S1375 (daily ed. Mar. 8, 2011) (statement of Sen. Kyl)”.  Id. at 7.  While Praxair argued that it had conducted “diligent searches” and presented an “Exemplary List of Search Results from Cardinal Intellectual Property, Inc.” to support its argument, the PTAB found “scant evidence that Praxair engaged ‘a skilled searcher conducting a diligent search’ as contemplated by the legislative history.”  Id. at 9.  The PTAB also relied on the testimony of Praxair’s technical expert as evidence that “the newly-asserted references are not obscure texts unlikely to be discovered upon a reasonably diligent search of the relevant prior art.”  Id. at 9.

With respect to § 325(d), the PTAB concluded that Praxair’s underlying argument was “essentially the same” as that previously raised in the first IPR.  Id. at 12-13.  Thus, in addition to concluding Praxair was estopped under § 315(e)(1) from making arguments that it could have made in the first IPR, it exercised its discretion under § 325(d) to deny the second petition.  Id. at 13.

While the PTAB’s decision provides some indication of when and how the “reasonably could have been raised” estoppel will be applied when “new” prior art is relied on in a subsequent IPR, there remains substantial uncertainty about what evidence is sufficient to establish when that prior art is or is not “prior art which a skilled searcher conducting a diligent search reasonably could have been expected to discover.”  We will have to stay tuned to see how the PTAB further defines the contours of the “readily identified” standard that it applied to the new prior art relied on in this case and how it assesses evidence of “diligence in searching” in future IPRs.