In the most recent action in Depomed, Inc. v. Purdue Pharma LP, a patent infringement case involving pain reliever OxyContin, Purdue Pharma asked the U.S. District Court for the District of New Jersey to confirm that certain of the defenses it raised under 35 U.S.C. §§ 102 and 103 remained after a decision in the inter partes review (IPR) proceedings pertaining to the same patent. Depomed offered several theories to prevent Purdue from pursuing the various infringement defenses it had raised.

First, the court denied Depomed’s theory of statutory estoppel. Depomed had argued that Purdue could have raised these defenses in the IPR, arguing that the current on-sale bar issue related to the MS Contin® product could have been argued in the IPR based on documentation about the MS Contin® product.

The court noted that “Inter partes review cannot replace the district court in all instances, for example, when claims are challenged in district court as invalid based on the on-sale bar…” Quoting Synopsys, Inc. v. Mentor Graphics Corp. Purdue argued that its on-sale bar and § 102(g) defenses were not based solely on patents or printed publications. Rather, the publications were used to support its contentions that “the claimed invention was on sale prior to the filing of the patents-at-issue, or invented by another before that time.” The court agreed that using the publications for support did not transform these defenses “into a statutory ground for relief in an IPR.”

The court also declined Depomed’s argument that Purdue adopted its position in bad faith.  The court noted that throughout the case Purdue had argued that a stay pending the IPR matter would streamline the invalidity issues in the litigation matter.

Finally the court denied Depomed’s theory of judicial estoppel due to statements Purdue made in an effort to obtain the stay pending the IPR. While noting that the court appreciated Depomed’s frustration at having to litigate issues already presented to the Patent Trial and Appeal Board (PTAB), it could not “ignore the fact that the Federal Circuit has determined that it is appropriate to do so.” The court noted that the IPR proceedings reduced the number of defenses and references that remained available to Purdue in the litigation matter.