Although Inter Partes Review (IPR) is limited to grounds of unpatentability based upon prior art references, it is nevertheless possible to raise issues of written description or enablement by applying intervening prior art that is published between two priority dates for a claimed invention. Such intervening prior art may even be applied between two filing dates created by a continuation application, even though no new material has been introduced into the application with the later filing date.  In re NTP, 654 F.3d 1279 (Fed. Cir. 2011).  The Board has specifically held that entitlement to priority is appropriately determined in the context of an IPR.  See IPR2013-00323, paper no. 62, citing In re NTP. 

Recent Cases

This approach has now been applied in several further IPRs with mixed results. For example, the petitioners relied on intervening prior art in IPR2014-00315 and IPR2015-00291. While the Board did not institute IPR in the former petition, it did institute IPR in the latter.  One reason appears to be that the petition in IPR2015-00291 included a new expert declaration specifically addressing the factors required to evaluate written description and enablement of the specification of the patent at issue, constituting new evidence not previously considered in original prosecution. By contrast, in IPR2014-00315, the petition used arguments that had already been considered in the original prosecution of the patent at issue.

This intervening art tactic may be particularly useful in the life sciences area, as illustrated by IPR2015-00291. There have been recent decisions by the Federal Circuit in relation to written description and lack of enablement that may create opportunities for life sciences patents to be attacked with this approach. One such decision is Ariad Pharmaceuticals v. Eli Lilly (Fed. Cir. 2010) (en banc), which was cited by the Board in its decision instituting IPR in IPR2015-00291.  Life sciences patents involving antibodies, immunotherapy, stem cell and regenerative medicine technology have all been recent targets of IPRs.

Importance of Experts

Petitioners will likely need to enlist the assistance of newly retained experts to apply the factors enumerated by the Federal Circuit for determining lack of written description or lack of enablement in order to prepare successful petitions based on this tactic.  In situations where related applications or the original application underlying the patent targeted in IPR have already encountered enablement or written description issues during prosecution, then it is important for the petition to distinguish how a new issue is presented, which may be accomplished through identifying differences between the prior situations and those in the petition, expert declarations utilizing new evidentiary exhibits, or a combination of those approaches.