By Yang Li Ph.D. (Alex) and Matt Johnson

Among the many differences from a patent litigation in a district court, the expedited nature of an inter partes review (IPR) brings with it an obligation for the petitioner to have a full-fledged legal theory of its case right from the start.  Unlike a district court litigation where parties are free to develop and revise their arguments over the course of litigation and in response to newly discovered material, a petitioner in an IPR must demonstrate with particularity why the patent it challenges is unpatentable from the onset of the proceedings in the petition to institute.  The Patent Trial and Appeal Board (PTAB) does not allow a petitioner to make a new argument of unpatentability midcourse in an IPR.

The prohibition against shifting arguments is demonstrated in Pfizer v. Chugai Pharmaceutical, Case No. IPR2017-01357 (PTAB Nov. 28, 2018).  In this case, Pfizer challenged a patent for a method for purifying proteins on the ground that it was anticipated by a prior art reference Shadle.  Regarding a key claim limitation (“eluting the antibody with an acidic aqueous solution of low conductivity having a molarity of 100 mM or less”), Pfizer originally contented that Shadle expressly disclosed the limitation, but in response to arguments on claim construction, it shifted its argument in Reply to that Shadle met the claim limitation inherently regardless of the claim construction.  Pfizer also updated its expert testimony to support the inherency argument.

The Board did not accept the inherency argument and faulted the petitioner Pfizer for its “belated change of course.”  The Board explained that “the introduction of new evidence in the course of a trial is to be expected in inter partes review trial proceedings,” but “the shifting of arguments is not.”  Pfizer’s inherency theory was an “impermissible shift of its anticipation theory” because rather than “explaining how its original petition was correct,” the inherency argument amounted to “a new theory . . . absent from the petition.”  For this and other reasons, the Board concluded that Pfizer did not meet its burden of showing unpatentability, and the patent in question ultimately survived the IPR unscathed.


The Pfizer case highlights the specialized nature of inter partes review and its contrast with district court litigations.  Full preparation for the case from all angles is a must for petitioners.

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Matt Johnson is one of the Firm's primary contacts on practice before the PTAB. Matt consults on nearly every one of Jones Day's over 290 PTAB cases to date. He currently serves as co-chair of Jones Day's PTAB practice.