PTAB Rejects ANDA-Filer’s IPR Challenge to Endo’s Opana ER Patent, Finds Limitations Not Inherently Disclosed in Prior Art

On July 22, 2015, the Patent Trial and Appeal Board rejected Amneal Pharmaceuticals LLC’s America Invents Act (AIA) challenge to Endo Pharmaceuticals’ patent related to Opana ER. The patent at issue (the ‘216 patent) relates to oral controlled-release pharmaceutical formulations comprising oxymorphone and methods of using it for sustained pain relief. In its Final Written Decision, the Board held that the ‘216 patent was not invalid.

The Litigation. Endo filed suit against Amneal and others in November 2012, alleging that their ANDAs for Opana ER would infringe three of Endo’s patents (the ‘216, ‘122, and ‘482 patents). Amneal filed for inter partes review (“IPR”) of all three asserted patents.[1] The district court issued an order on August 13, 2014 allowing counsel representing Endo in the litigation to collaborate with counsel representing Endo in the IPR proceedings, though Endo’s litigation counsel was restricted from (1) amending, drafting, or consulting with Endo or IPR counsel regarding the amendment of patent claims, and (2) sharing with IPR counsel any information designated confidential under Amneal’s protective order.

The IPR.  The Board began its analysis by addressing claim construction. Amneal contended that the broadest reasonable construction of “controlled release” encompasses formulations that “release no more than about 80% of their active pharmaceutical ingredients within 60 minutes under the claimed dissolution conditions.” Amneal also argued that “about” encompasses “at least the standard statistical error” for dissolution testing values. Endo responded that no claim construction was necessary. The board held that Amneal’s proposed constructions were the broadest reasonable construction of the disputed phrases in light of the specification.

The Board next reviewed whether four claims of the ‘216 patent would have been obvious over Maloney, a prior art reference teaching a controlled-release dosage form comprising oxymorphone. Amneal argued that Maloney inherently disclosed the recited “two or three peaks” of oxymorphone. Endo responded that multiple peaks are not inherent to all oxymorphone compositions and produced evidence indicating that certain formulations present only one peak oxymorphone plasma concentration. The Board concluded that Amneal did not establish that the multiple peaks limitation was inherently disclosed, and thus Amneal did not demonstrate the unpatentability of the claims over Maloney.

The Board then reviewed whether the claims would have been obvious over a patent titled “Extruded Orally Administrable Opioid Formulations” (“Oshlack”) and the Handbook of Dissolution Testing (“the Handbook”). Amneal argued that the in vitro dissolution profiles disclosed in Oshlack overlap the profiles recited in the challenged claims. The claims require specified in vitro release profiles, determined using the Paddle Method at 50 rpm.  But Oshlack provided an in vitro release using the Basket Method at 100 rpm.  Amneal argued that, based on the Handbook, the Paddle method at 50 rpm is “roughly equivalent” to the Basket method at 100 rpm, and thus the claims are obvious. Endo presented ample evidence indicating that the two methods are not equivalent. The Board stated that the method recited in Oshlack, on its face, is not the same as the method recited in the challenged claims, so Oshlack does not expressly disclose a controlled-release oxymorphone formulation having the recited dissolution profile. As such, Amneal relied, at least in part, on an inherency argument. The Board concluded that Amneal did not present sufficient evidence to establish that the challenged claims would have been obvious over Oshlack and the Handbook.

Takeaways. The Board’s decision illustrates the challenges associated with inherency-based arguments and the importance of presenting sufficient evidence to demonstrate that an inherent disclosure is necessarily present in the prior art.  Experimental evidence is very helpful when attempting to prove inherency, and its absence here could have been the difference between a win and a loss.  Perhaps this is something that will be addressed in the litigation.

In that regard, Amneal was one of many codefendants in the litigation—raising questions of whether any codefendants could be estopped from relying on the same references after the IPR decision. In general, an entity must actively participate in the request for reexamination before it becomes a “real party in interest” to the proceedings. Mere membership in a joint defense group with a petitioner does not automatically render a party a real party in interest.[2]  There is, however, no bright-line test for determining whether a codefendant is a real party in interest.[3]  One codefendant, Actavis, has filed a letter asking the judge overseeing the litigation to disregard the Board’s decision, arguing that Actavis was not a party to the PTO proceeding, it intends to present different evidence at trial than what was presented to the Board, and it plans to present an invalidity argument that was not raised in the IPR.


[1] The PTAB determined that the IPR involving the ‘122 patent could not be instituted because the Petition was filed more than one year after the complaint was served on Amneal. The PTAB granted Endo’s request for adverse judgment in the IPR related to the ‘482 patent.

[2] The Board has stated that “a search for prior art, review of possibly useful prior art, preparation of an invalidity defense based on found and evaluated prior art to support a litigation defense, and financial support to carry out a litigation defense – do not amount to participation in a request for reexamination based on such activities, where the activities are conducted with only an intent to defend the litigation suit. Evidence that the activities were conducted with an intent to file an inter partes reexamination request is required, in order for a petitioner to establish that other defendants (codefendants) are real parties in interest in a request for reexamination.” Reexamination Control No. 95/001,852 (emphasis added).

[3] The PTO’s Trial Practice Guide explains that “if Party A is part of a Joint Defense Group with Party B, and Party B files a [post-grant review] petition, Party A is not a ‘real party-in-interest’ or a ‘privy’ for the purposes of the PGR petition based solely on its participation in that Group. That is not to say that Party A’s membership in . . . the Joint Defense Group . . . is irrelevant to the determination; deeper consideration of the facts in the particular case is necessary to determine whether Party A is a ‘real party-in-interest’ or a ‘privy’ of the petitioner.” 77 Fed. Reg. 48759-60 (Aug. 14, 2012).