The doctrine of equivalents is a judicially-created form of infringement whereby an accused product or process that fails to literally infringe a patent claim may nonetheless be found to infringe if there is an “equivalence” between the elements of the accused product or process and the claimed elements of the patented invention. See, e.g., Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., Ltd., 535 U.S. 722 (2002); Warner-Jenkinson Co. v. Hilton Davis Chem. Co., 520 U.S. 17, 21, 29 (1997). The doctrine of equivalents is limited, however, by a number of exceptions including prosecution history estoppel and the disclosure-dedication doctrine.

The disclosure-dedication doctrine bars infringement under the doctrine of equivalents where the equivalent element (found in the accused product or process) was disclosed but not claimed in the asserted patent. See Johnson & Johnston Assocs., Inc. v. R.E. Service Co., Inc., 285 F.3d 1046, (Fed. Cir. 2002) (en banc). As explained by the Federal Circuit in Johnson, the policy behind the disclosure-dedication doctrine is to prevent patent owners from limiting the claimed invention during prosecution and then subsequently relying on the doctrine of equivalents to recapture the non-claimed subject matter during enforcement. Id. at 1054 (stating that “a patentee cannot narrowly claim an invention to avoid prosecution scrutiny by the PTO, and then, after patent issuance, use the doctrine of equivalents to establish infringement because the specification discloses equivalents”).

On May 8, 2020, the Federal Circuit (“Court”) issued a precedential opinion in Eagle Pharmaceuticals Inc. v. Slayback Pharma LLC affirming that a patent owner’s claims for infringement under the doctrine of equivalents were barred by the disclosure-dedication doctrine. This decision illustrates that an equivalent element that is disclosed in a patent application, but not claimed, can foreclose the doctrine of equivalents even when the equivalency is not described in the context of the claimed invention.

Eagle Pharmaceuticals Inc. (“Eagle”) sued Slayback Pharma LLC (“Slayback”) for infringing several patents under the doctrine of equivalents. Claim 1 of U.S. Patent No. 9,572,796, shown below, is representative of the asserted patents at issue in Eagle Pharma.

1. A non-aqueous liquid composition comprising:

bendamustine, or a pharmaceutically acceptable salt thereof;

a pharmaceutically acceptable fluid comprising a mixture of polyethylene glycol and propylene 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;

wherein the composition has less than about 5% total impurities after 15 months of storage at about 5° C., as calculated on a normalized peak area response basis as determined by high performance liquid chromatography at a wavelength of 223 nm.

Because the accused product included ethanol instead of the propylene glycol contained in the “pharmaceutically acceptable fluid” of Claim 1, Eagle relied upon the doctrine of equivalents and argued that the ethanol contained in the accused product is equivalent to the propylene glycol.

Slayback countered that the disclosure-dedication doctrine barred Eagle’s claim of infringement under the doctrine of equivalents, because the asserted patents disclose but do not claim ethanol as an alternative solvent to propylene glycol.

In response, Eagle argued that the disclosure-dedication doctrine should not apply to the ethanol disclosed in the asserted patents, because the equivalency of ethanol was not disclosed in the context of embodiments containing the “antioxidant” of Claim 1. Instead, the asserted patents disclose the use of ethanol in bendamustine formulations containing “chloride salts” (as opposed to the “antioxidant” of Claim 1).

Because the asserted patents disclose three categories of formulations having separate ingredients and purportedly working in different ways, Eagle argued that a skilled artisan would not consider ethanol to be an alternative to propylene glycol in the antioxidant-containing formulations of Claim 1.

The Court was not persuaded by the patent owner’s arguments for three reasons.

First, in Johnson the Federal Circuit rejected an “embodiment-level approach” to the disclosure-dedication doctrine. Johnson, 285 F.3d at 1052. The Court in Eagle Pharma explained 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.”

Second, the Federal Circuit has previously held that the disclosure-dedication doctrine requires only that the specification disclose the unclaimed subject matter “as an alternative to the relevant claim limitation.” Pfizer, Inc. v. Teva Pharma. USA, Inc., 429 F.3d 1364, 1378 (Fed. Cir. 2005) (emphasis added).

Although the general disclosures of the asserted patents in Eagle Pharma appear to confine their description of ethanol to the embodiments containing a chloride salt (as opposed to the antioxidant of Claim 1), the Court found that the descriptions still apply to the embodiment of Claim 1 because the descriptions clearly teach the equivalency of ethanol and propylene glycol in the context of a “pharmaceutically acceptable fluid.”

Third, unlike the claim limitation at issue in Pfizer that recited a specific function of the equivalent element that differed from the function described in the specification, the claim limitation at issue in Eagle Pharma only required the fluid to be “pharmaceutically acceptable.”

Because the asserted patents in Eagle Pharma repeatedly disclose the use of ethanol as a “pharmaceutically acceptable fluid,” the Court held that the asserted patents had dedicated ethanol to the public by disclosing but not claiming it as an alternative to propylene glycol in the “pharmaceutically acceptable solvent” limitation of Claim 1–regardless of the other limitations included in the claimed invention.

Takeaways:  Species that are disclosed in the specification as being equivalent can bar the doctrine of equivalents if they are not claimed. Therefore, it is prudent to enumerate functionally-equivalent species in the claims. If the species are functionally-equivalent in only certain contexts, then it can be important to explain the functional differences in the disclosure, and to specify the function of a recited specie in the claims.

Judges: K.M. O’MALLEY, J.V. REYNA and R.T. CHEN (Opinion by REYNA)