Purdue Pharma L.P. v. Collegium Pharm., Inc.

Case Name: Purdue Pharma L.P. v. Collegium Pharm., Inc., No. 15-cv-13099, 2018 U.S. Dist. LEXIS 167895 (D. Mass. Sept. 28, 2018) (Saylor, J.) 

Drug Product and Patent(s)-in-Suit: Xtampza® ER (oxycodone); U.S. Patents Nos. 9,073,933 (“the ’933 patent”), 8,652,497 (“the ’497 patent”), and 9,155,717 (“the ’717 patent”)

Nature of Case and Issue(s) Presented: The ’933 patent claims both a product (an oxycodone composition) and a process for preparing the product by removing a source of 14-hydroxy from that product. The ’497 and ’717 patents (“the irritant patents”) share a specification and are directed to an opioid analgesic with an irritant that imparts a burning or irritating effect to an abuser and is intended to prevent abuse of the oral dosage form. Collegium filed for summary judgment, arguing that: (i) the ’933 patent is invalid under issue preclusion; (ii) it cannot infringe the ’933 patent because its product does not contain oxycodone hydrochloride; and (iii) it cannot infringe the irritant patents because its product does not contain an irritant.

Why Purdue Prevailed as to the ʼ933 Patent: Based on a prior invalidity finding of parent patents (“Low-ABUK Patents”), Collegium argued that Purdue was estopped from asserting the ’933 patent. During prosecution of the ’933 patent, Purdue filed a terminal disclaimer to the Low-ABUK Patents, but the court concluded that an obviousness-type double-patenting inquiry involves only a claim-to-claim comparison of the first-filed patent and the later filed-patent. Such an inquiry does not involve a detailed analysis of whether individual claim limitations would materially affect obviousness if they are selectively added to or subtracted from consideration. The court explained that this inquiry is what is required for the “same issue” prong of issue preclusion. Whether the invalidity decision of the Low-ABUK Patents in the prior district court decision should be given preclusive effect presented “a much closer call.” The court noted that there were several differences in the claim limitations of the Low-ABUK Patents and the ’933 patent, but explained that the materiality of those limitations was very much in doubt. Nevertheless, a genuine fact dispute existed, and summary judgment was not warranted at this juncture.

Collegium also argued that it was entitled to summary judgment of non-infringement of the ’933 patent because prosecution-history estoppel precluded Purdue from arguing that Collegium’s oxycodone myristate is the equivalent of oxycodone hydrochloride, and that it does not infringe under the doctrine of equivalents because oxycodone myristate does not perform the same function as oxycodone hydrochloride. As to the former, the court concluded that Purdue may have disclaimed products including oxycodone free base, but that it was unclear that it surrendered all other forms of oxycodone, including Collegium’s oxycodone myristate. Further, the court explained that Wm. Wrigley Jr. Co. v. Cadbury Adams USA LLC, 683 F.3d 1356 (Fed. Cir. 2012) did not prevent application of the doctrine of equivalents because the record evidence did not demonstrate that the inventors were aware of the interchangeability of oxycodone myristate when they chose to narrowly claim only oxycodone hydrochloride. Finding that prosecution-history estoppel did not apply at this time, the court concluded that Purdue presented a genuine issue of disputed material fact as to whether oxycodone myristate performs substantially the same function as oxycodone hydrochloride. Therefore summary judgment of non-infringement was not warranted.

Why Collegium Prevailed as to the Irritant Patents: Collegium argued that it was entitled to summary judgment of non-infringement because the myristic acid in Xtampza ER was not an irritant. Purdue argued that the high ratios of myristic acid to oxycodone base, as well as the fact that any excess myristic acid remains in the product, supports its claim that Collegium infringes. Collegium responded that all of the myristic acid in its formulation was necessary to solubilize oxycodone and drive salt formation. The court noted that an in vitro volitization study and an intranasal study produced results showing that Xtampza ER may cause irritation when abused. Nevertheless, the court looked to the prosecution history to find that Purdue clearly and unambiguously expressed surrender of excipient functions that overlap—for example, an excipient could not have the function as both a pharmaceutical excipient and an irritant. The court explained that Purdue “does not (and likely could not) claim every composition that happened to have an irritating quality under some set of circumstances, whether or not the irritant was a separate component.” As a result, Collegium did not infringe the irritant patents.