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  • Shelly M. Fujikawa

The Importance of Continuations

Eagle Pharmaceuticals appealed to the Federal Circuit after, based on the pleadings, a district court held that Slayback Pharma LLC’s pharmaceutical formulation did not infringe four patents asserted by Eagle. The recitation “a pharmaceutically acceptable fluid comprising…polyethylene glycol” in the claims of these patents was at issue. Eagle argued that Slayback’s formulation, containing ethanol as the pharmaceutically acceptable fluid, infringed under the doctrine of equivalence because the ethanol in the Slayback product was insubstantially different from polyethylene glycol. Slayback argued that its formulation did not infringe under the disclosure-dedication doctrine because the asserted patents repeatedly disclosed ethanol as an alternative “pharmaceutically acceptable fluid” to polyethylene glycol, but did not claim the same. Eagle further argued that the asserted patents only disclosed ethanol as an alternative to polyethylene glycol for unclaimed formulation embodiments and, thus, the disclosure-dedication doctrine did not apply.

In determining whether the disclosure-dedication doctrine applied, the Federal Circuit asked whether the specification described the unclaimed subject matter “as an alternative to the relevant claim limitation.” The Federal Circuit reasoned that the specification repeatedly stated that ethanol was an alternative pharmaceutically acceptable fluid to polyethylene glycol “without qualification.” Thus, the Federal Circuit held that ethanol, as a pharmaceutically acceptable fluid in the asserted patents, was dedicated to the public and could not be used to assert infringement under the doctrine of equivalence.

This case may remind patent prosecutors that narrow claim limitations generally enable a competitor to work around the claims to yield a product that does not infringe. If a patent is of particular commercial importance, having a continuation pending may be useful to remedy flaws found during litigation. Indeed, Eagle has filed a continuation from one of the four asserted patents, U.S. Patent No. 10,010,533, in July 2019. It is currently awaiting examination.


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