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The Eagle has Landed: Federal Circuit Affirms Disclosure-Dedication Doctrine Barring Doctrine of Equivalents in Eagle Pharmaceuticals v. Slayback Pharma LLC


The Federal Circuit upheld the US District Court for the District of Delaware’s decision that generic Slayback Pharma did not infringe Eagle Pharmaceutical’s patents covering its anti-cancer drug, BELRAPZO®, because Eagle was barred from applying the doctrine of equivalents under the disclosure-dedication doctrine to capture Slayback’s generic product, which included ethanol instead of the claimed propylene glycol (PG). The court found that Eagle disclosed ethanol as an alternative solvent to PG, but failed to claim it, thereby dedicating ethanol to the public. The court also determined that the application of the disclosure-dedication doctrine was permitted at the pleadings stage.

Issue Presented

Slayback prevailed in district court on a Rule 12(c) motion (motion for judgment after pleadings are closed) on the issue of infringement because the court agreed that Eagle was barred under the disclosure-dedication doctrine from relying on the doctrine of equivalents (DOE). Slayback used ethanol instead of PG as a second solvent in its generic drug, which Eagle had asserted infringed under the DOE. The district court found that Eagle had disclaimed ethanol as a viable equivalent by disclosing it in the written description but not claiming it, thus barring Eagle from relying on the DOE. On appeal, Eagle argued that the district erred in two ways: (1) on the merits of the disclosure-dedication doctrine; and (2) in incorrectly applying the disclosure-dedication doctrine at the pleadings stage because factual disputes remained.

Asserted Patents

Eagle filed suit in the US District Court for the District of Delaware, arguing that Slayback infringed four patents (US Patent Nos. 9,265,831, 9,572,796, 9,572,797, and 10,010,533) with its abbreviated new drug application (ANDA) for a generic version of Eagle’s BELRAPZO®, a bendamustine product for treating chronic lymphocytic leukemia and indolent B-cell, non-Hodgkin lymphoma. Eagle’s asserted patents disclose and claim improved ready-to-use bendamustine-containing compositions with enhanced long-term storage capabilities which employ two solvents, polyethylene glycol (PEG) and propylene glycol (PG), as a “pharmaceutically acceptable fluid.” Slayback’s generic includes PEG but it uses ethanol instead of PG as the second component of its solvent system.    

Claim 1 of the ‘796 patent is representative:

  1. A non-aqueous liquid composition comprising:

bendamustine, or a pharmaceutically acceptable salt thereof;

a pharmaceutically acceptable fluid comprising a mixture of polyethylene glycol andpropylene glycol, wherein the ratio of polyethylene glycol to propylene glycol in the pharmaceutically acceptable fluid is from about 95:5 to about 50:50; and

a stabilizing amount of an antioxidant…

The District Court’s Decision

Slayback prevailed in district court on its Rule 12(c) motion for noninfringement. Eagle advanced two arguments to support its position that Slayback could not rely on the disclosure-dedication doctrine to bar Eagle’s reliance on DOE to establish infringement. First, Eagle argued that Slayback’s use of the disclosure-dedication doctrine was not appropriate at the Rule 12(c) stage based on Federal Circuit precedent. The court dismissed this argument, ruling that Eagle’s interpretation was incorrect and that the court is allowed to decide questions of law, including those involving the disclosure-dedication doctrine, at the Rule 12(c) stage.   

Second, Eagle argued that Slayback did not meet the conditions of the disclosure-dedication doctrine because Eagle’s disclosure of ethanol (Slayback’s second solvent and the alleged equivalent of PG of the asserted claims) did not pertain to the claimedembodiment of the asserted claims, but rather to a different embodiment that was not claimed. According to Eagle, it was not the case that ethanol was disclosed and then notclaimed, but rather that ethanol was not disclosed with respect to the claimed embodiment. Thus, Eagle argued that the disclosure-dedication doctrine did not apply to bar Eagle from asserting that Slayback’s use of ethanol infringed the recited propylene glycol limitation under the DOE.

This argument failed. The court found that “the written description of the asserted patents unambiguously and repeatedly identifies [ethanol] as an alternative to propylene glycol.” And, because ethanol was unambiguously disclosed as an equivalent of PG, but not claimed, Eagle was properly barred under the disclosure-dedication doctrine from asserting infringement under the DOE with regard to ethanol being an equivalent of propylene glycol.

The court also clarified that it was immaterial whether the disclosure of ethanol was associated with a different embodiment that was not claimed. The focus on the analysis, according to the court’s precedent, was whether the ethanol was described as a suitable equivalent in the context of the claim limitation at issue (i.e., PG). According to the court, disclosure-dedication doctrine is not based on embodiments, but rather on claim limitations, per Federal Circuit precedent (e.g., setting forth that “the disclosure-dedication doctrine applies to unclaimed subject matter that is ‘identified by the patentee as an alternative to a claim limitation.’” citing to Pfizer, Inc. v. Teva Pharm. USA, Inc., 429 F.3d 1364, 1379 (Fed. Cir. 2005)). 

The court also pointed to Federal Circuit precedent in Johnson & Johnston (Fed. Cir. 2002) in which the court had rejected the same argument now raised by Eagle. The district court stated that “the disclosure-dedication doctrine is not restricted to disclosures of embodiments and that the doctrine applies to claim limitations.” Because Eagle’s patent disclosure clearly disclosed ethanol as a suitable alternative to the PG limitation, even though it was in connection with an embodiment different from the claimed embodiment, Eagle’s reliance on DOE was properly barred by the disclosure-dedication doctrine.

The Federal Circuit’s Decision

Eagle appealed the district court’s ruling on two issues. First, Eagle challenged “the merits of the district court’s determination that the disclosure-dedication doctrine bars Eagle’s infringement claims under the doctrine of equivalents.” Second, Eagle challenged the district court’s ruling on procedural grounds, namely, that a factual dispute existed at the time of entering judgment against Eagle on the Rule 12(c) motion on the pleadings. According to Eagle, the factual dispute was whether a skilled artisan would have understood the specification to have disclosed ethanol as a valid equivalent of PG in the claimed invention.

Issue I: On the merits

The Federal Circuit agreed with the district court that “the asserted patents dedicated ethanol to the public by disclosing, but not claiming, ethanol as an alternative to PG in the ‘pharmaceutically acceptable solvent’ claim limitation.” The court noted that the written description “repeatedly identified—without qualification—ethanol as an alternative pharmaceutically acceptable fluid” and that “nothing in the specification suggests that these repeated disclosures of ethanol are limited to certain formulations, or that they do not extend to the claimed formulation.” In further support, the court held that the “disclosure-dedication doctrine does not require the specification to disclose the allegedly dedicated subject matter in an embodiment that exactly matches the claimed embodiment”  but instead only requires that the “specification disclose the unclaimed matter ‘as an alternative to the relevant claim limitations.’” 

The court rejected Eagle’s argument that the disclosed (but unclaimed) chloride salt category of formulations (which expressly includes ethanol) “work by a different mechanism than the claimed antioxidant formulations, and thus a skilled artisan would understand that ethanol does not relate to the claimed invention.” The court emphasized that the claim limitation of a “pharmaceutically acceptable fluid” has only one stated purpose - that it be pharmaceutically acceptable, and the specification repeatedly disclosed ethanol as being a pharmaceutically acceptable fluid. The court therefore held that the asserted patents “dedicated ethanol to the public by disclosing, but not claiming, ethanol as an alternative to PG in the “pharmaceutically acceptable solvent” claim limitation and thus, affirmed the district court’s decision on this issue.

Issue II: Procedural

Eagle also challenged the district court’s decision on procedural grounds.  According to Eagle, a fact was still in dispute when the district court entered its Rule 12(c) judgment in favor of Slayback. The fact in dispute, alleged by Eagle, was “whether a skilled artisan would understand the specification to disclose ethanol as an alternative to PG in the claimed invention.” In particular, Eagle contended that the court erred by “improperly ignoring Dr. Amiji’s declaration [Eagle’s expert], which was ‘the best (and only) evidence of a skilled artisan’s understanding of [the] disclosure.’” The federal court rejected this challenge, finding that the district court was correct in setting aside Eagle’s expert’s testimony because that testimony “was merely ‘an attempt to manufacture a factual dispute.’” The court further emphasized that application of the disclosure-dedication doctrine is a question of law, and added that expert testimony is not required for a court to determine “how a skilled artisan would understand a patent’s disclosure and claimed invention.” In other words, that the court was not required to accept the expert’s opinion, and could substitute its own understanding of the patent’s disclosure if the patent’s disclosure is “easily understandable” without expert explanation. The Federal Circuit consequently found that the district court did not err by deciding non-infringement at the pleadings stage on the Rule 12(c) motion.


  • This decision is a reminder that the disclosure-dedication doctrine does not require disclosure of the dedicated subject matter in the context of an embodiment that exactly matches the claimed embodiment – what matters is whether the dedicated subject matter is disclosed as an equivalent or alternative to a specific limitation in the context of any.

  • Issues involving the disclosure-dedication doctrine may be decided at the conclusion of the pleadings stage. In addition, a court is not required to consider expert testimony to resolve disclosure-dedication doctrine issues.

  • Patent drafters should be judicious when preparing patent applications having disclosures that are broader than the scope of their claims. There is a risk that any subject matter disclosed but not claimed will be dedicated to the public; thus, consideration should be given as to whether the disclosed subject matter has a purpose with respect to the sought-after claims.

  • Patent drafters should consider matching the scope of the sought-after claims with the scope of the specification in order to avoid triggering the disclosure-dedication doctrine as to subject matter disclosed but not claimed. If alternatives to claimed features are to be disclosed (e.g., a list of alternative formulation components), then consideration should be made to claim these alternatives, particularly where they potentially may cover competitive and/or commercial embodiments.

  • Eagle disclosed numerous formulation embodiments without disclosing a generic concept broadly covering those embodiments. Drafters should try to describe and claim alternative or equivalent elements more generically whenever possible so as to avoid implication of the disclosure-dedication doctrine.

  • In the case of broad disclosures containing more subject matter than was claimed, consideration should be given to maintaining a pending application to allow for opportunities to obtain claims to subject matter not previously claimed. This may maximize the chances of ensnaring a competitor product or process without relying on the doctrine of equivalents.