Purdue alleges that Collegium infringed three patents relating to abuse-deterrent extended-release oxycodone by filing an NDA for Collegium’s XTAMPZA ER product. Collegium sought summary judgment of non-infringement on two theories – that its active ingredient (oxycodone myristate) is not the equivalent of Purdue’s oxycodone hydrochloride, and that Collegium’s product lacks the claimed “irritant.” Collegium also asserted that one of the patents should be deemed invalid under issue preclusion or collateral estoppel, based on a final judgment in a New York court that three related patents were invalid and the PTO’s requirement, during examination of the patents at issue, that a terminal disclaimer be filed to overcome obviousness-type double patenting over the related patents.
The invalidated claims from the prior litigation were all product-by-process claims; while the Judge in that case acknowledged the process was novel, the claims stood or fell based solely on the product limitations, which did not describe a patentably-distinct compound. In evaluating the collateral estoppel argument, Judge Saylor noted that it had not been applied by the District of Delaware in an infringement case involving one of the patents of this suit. Judge Saylor applied Federal Circuit law on the preclusion and estoppel issues, which allows for preclusion on patent invalidity where the differences between the unadjudicated and adjudicated claims do not materially alter the question of patentability. He determined that the PTO’s double patenting analysis fails to satisfy this requirement, and that Purdue’s filing of the terminal disclaimers (particularly while expressly indicating its lack of agreement with the rejections) could not be converted into an admission or acquiescence on the merits of the rejections. He also determined that the claims at issue included additional limitations that materially alter the patentability as compared with the previously-invalidated claims, as the new claims included limitations relevant to the process that were not considered in the New York litigation. Collegium asserted that these limitations were inherently present in the invalidated Purdue patents, but Judge Saylor declined to apply the doctrine of inherency where the references in question, related Purdue patents, would not qualify as prior art, and noted that in any event there were unresolved issues of material fact that precluded summary judgment on the issue. While rejecting the preclusion issue, Judge Saylor did note that the findings of fact by the New York court rendered the validity of at least some of the asserted claims doubtful.
Collegium next sought to apply prosecution history estoppel to preclude a finding of infringement by equivalents, asserting that Purdue had specifically distinguished its hydrochloride form of oxycodone over other forms of oxycodone. Judge Saylor, however, determined that the scope of disavowal extended not further than products including oxycodone free base and declined to estop the equivalency argument. He found factual issues as to whether the two forms were equivalent that precluded summary judgment of non-infringement.
Collegium sought judgment of non-infringement on method claims, asserting that it does on itself complete all of the method steps because its product is manufactured by two companies that it does not control; Judge Saylor determined that Collegium could not demonstrate an absence of material fact on this issue, and denied summary judgment. Collegium’s last effort was to escape infringement of two of the patents on the basis that the myristic acid it utilized in its product is not an “irritant,” but instead is included to dissolve the oxycodone base. Looking back to the construction of “irritant,” the Court noted that Purdue had disavowed from the scope of that term components that both served both as an irritant and provided some other benefit, such as serving as an excipient. Noting that Purdue concedes that myristic acid in the XTAMPZA ER provides an excipient function, Judge Saylor granted summary judgment of non-infringement of all claims requiring an irritant, which effectively resulted in non-infringement on two of the three asserted patents.