In Depomed, Inc. v. Purdue Pharma L.P. et al, 3-13-cv-00571, the District of New Jersey held that neither statutory nor judicial estoppel bars Purdue from continuing to assert invalidity defenses that were not instituted during inter partes review (“IPR”) of Depomed’s patents. The decision was prompted by Purdue’s motion to amend its Invalidity Contentions seeking: (1) leave to amend its contentions to assert indefiniteness of a claim term that was previously construed during the IPR proceedings; and (2) confirmation that its 35 U.S.C. §§ 102 and 103 defenses remain in the case despite the PTAB’s decisions upholding the validity of the asserted claims.

Depomed filed its complaint against Purdue on January 29, 2013, alleging that OxyContin® infringes several of its patents. Purdue served its Invalidity Contentions on September 3, 2013. Subsequently, Purdue filed three petitions for IPR challenging the asserted claims of the patents-in-suit, and on July 10, 2014, the PTAB instituted review on certain, but not all, grounds asserted in Purdue’s petitions. Meanwhile, Purdue successfully moved the district court to stay the litigation pending the final outcome of the IPRs. On July 8, 2015, the PTAB issued its final written decisions upholding the validity of each claim instituted for review. After an expedited appeal, the Federal Circuit affirmed the PTAB and the litigation stay was lifted. Shortly thereafter, the parties re-commenced litigation in the district court.

On June 1, 2016, Purdue moved the court for the following: (1) leave to amend its Invalidity Contentions to assert indefiniteness of one claim term, which was previously construed during the IPRs, and (2) confirmation that §§ 102 and 103 defenses that Purdue could not have reasonably raised during the IPR proceedings (i.e. defenses that were denied institution) remain in the case. Depomed opposed Purdue’s motion to amend to add indefiniteness, and made a cross motion to strike Purdue’s §§ 102 and 103 defenses as barred by statutory and/or judicial estoppel. The court granted Purdue’s motion and denied Depomed’s cross motion in its entirety.

With regard to indefiniteness, Purdue argued that although the claim term was previously construed, it had good cause to assert indefiniteness in view of the Supreme Court’s intervening decision in Nautilus, Inc. v. Biosig Instruments, Inc., 134 S.Ct. 2120, 189 L.Ed.2d 37 (2014). Prior to Nautilus, a patent claim need only be “amenable to construction,” and not “insolubly ambiguous” to be considered definite. Nautilus, 134 S.Ct. at 2124. In Nautilus, however, the Supreme Court changed the standard, holding that “a patent is invalid for indefiniteness if its claims, read in light of the specification delineating the patent, and the prosecution history, fail to inform, with reasonable certainty, those skilled in the art about the scope of the invention.” Id. It is not enough that a court can ascribe some meaning to the claim term. Id. at 2130. The district court was unpersuaded by Depomed’s argument that Purdue and the PTAB were able to construe the claim term at issue during the IPR proceedings. The court found that (1) indefiniteness under § 112 is not a ground on which a petitioner may request IPR; and (2) Purdue filed its petitions over 5 months prior to the Nautilus decision and thus had no reason to believe that the PTAB, which reviews claims under the “broadest reasonable interpretation” standard, would find the claim term indefinite.

Purdue also sought confirmation that the §§ 102 and 103 defenses that were not instituted during the IPRs remained viable. In its cross motion to strike, Depomed argued that the following defenses were barred by statutory estoppel: (1) § 102(b) on-sale bar and § 102(g) prior inventor defenses, which were not presented to the PTAB; and (2) defenses related to claims 11 and 12, which were not instituted for review on any ground. The court found that Purdue’s on-sale bar and 102(g) defenses were not based solely on patents or printed publications and thus could not be raised during the IPRs. The scope of IPR is limited to grounds “that could be raised under section 102 [anticipation] or 103 [obviousness] and only on the basis of prior art consisting of patents or printed publications.” 35 U.S.C. § 311(b). With regard to claims 11 and 12, the court, citing to Synopsys, Inc. v. Mentor Graphics Corp., 814 F.3d 1309, 1316 (Fed. Cir. 2016), determined that those claims were not subject to an IPR proceeding or a final written decision, thus Purdue is not statutorily estopped from challenging their validity in the district court.

The court also rejected Depomed’s argument that Purdue should be judicially estopped from litigating each of its §§ 102 and 103 defenses. In reaching this decision, the court stated, “where the PTAB chooses not to consider the merits of a defense raised in an IPR, that defense remains viable in litigation.”