Federal Circuit decision shows door not shut on infringement claims under the doctrine of equivalents in ANDA cases

Infringement under the doctrine of equivalents is a rare occurrence in Hatch-Waxman cases, but on 24^th June 2019, the Federal Circuit made just such a ruling, affirming a decision of the District Court of Delaware that held Watson and Actavis infringed UCB’s US Patent No 6,884,434. Given the court’s rejection of several arguments as to why UCB should be barred from alleging infringement under the doctrine, the case provides important strategic guidance on the doctrine for both patent prosecutors and litigators.

UCB sued Actavis for infringement of the ’434 patent and US Patent No 8,232,414 after Actavis filed an abbreviated new drug application (ANDA) for its generic version of rotigotine patches. The ’434 patent claims a transdermal patch containing an effective amount of rotigotine for the treatment of Parkinson’s syndrome. Claim 1 generally covers administration of rotigotine through a transdermal patch made of three layers: “The most relevant for this appeal being an adhesive layer in which an effective amount of the free base form of rotigotine is dissolved in an acrylate- or silicone-based polymer adhesive.”

Although Actavis’s patches do not contain acrylate- or silicone-based adhesive polymers, UCB argued, and the district court agreed, that Actavis’s polyisobutylene-based adhesive infringed the ’434 patent under the doctrine of equivalents.

On appeal, the Federal Circuit largely agreed with the district court’s findings.

First, the court held that prosecution history estoppel did not apply even though UCB elected - importantly, with traverse - to pursue claims that specified acrylate- or silicone-based adhesives over claims that did not specify a particular adhesive in response to an examiner’s restriction requirement. Although a restriction requirement can give rise to prosecution history estoppel, it did not here because the restriction requirement did not relate to polyisobutylene adhesive systems.

In other words, there was no surrender of particular adhesive systems or narrowing amendment made in response to the restriction requirement. Similarly, UCB was not precluded from asserting the doctrine of equivalents even though its inventor was aware of polyisobutylene adhesive systems, but chose to pursue narrower claims. The court acknowledged that foreseeability can foreclose equivalents arguments, but it does not act as an absolute bar against them. Here, there was no evidence that UCB distinguished acrylate- or silicone-based adhesives from polyisobutylene-based adhesives. Thus, there was no reason to conclude that UCB surrendered polyisobutylene-based adhesives as an equivalent.

Next, the court disposed of Actavis’s vitiation argument, holding that infringement by polyisobutylene-based adhesives under the doctrine of equivalents did not so broaden the claims that they would cover all adhesives. Rather, the district court made specific findings that there was no vitiation since polyisobutylene-based adhesives work just as well in place of the expressly-claimed “acrylate-based or silicone-based” adhesives in the invention, leaving open the possibility that other polymer-based adhesives may not qualify as equivalents.

Finally, the court rejected Actavis’s argument that UCB’s infringement theory ensnared the prior art because Actavis failed to identify a prior art reference that would be ensared by the inclusion of polyisobutylene-based adhesives. All of the prior art references identified by Actavis covered acrylate and silicone polymers, in addition to polyisobutylene. UCB’s infringement theory did not, therefore, ensare new prior art because the art identified by Actavis, if invalidating at all, would fall within the literal scope of the ’434 patent claims. With no basis for limiting application of the doctrine of equivalents, the district court’s infringement finding was affirmed, as were the remaining issues in the case.

Although infringement under the doctrine of equivalents has been difficult to prove in the pharmaceutical context, the door is not shut by any means. As this case illustrates, the doctrine remains a viable one, but there are numerous defences available to accused infringers faced with its application.

Prosecution history estoppel will, of course, continue to be front and centre, and patent applicants must be wary of how restriction practice could potentially result in a doctrine of equivalents bar. Important here was UCB’s response to the examiner’s restriction requirement with traverse, which the Federal Circuit relied on as evidence that UCB contested whether it was surrendering any equivalents.

Patent applicants must also keep in mind a potential accused infringer’s future arguments about “foreseeable” equivalents when drafting and prosecuting applications. Even though polyisobutylenes were known in the art at the time of UCB’s patent filing, the court nonetheless found insufficient evidence of surrender in the specification, claims and from the inventor’s knowledge.

Therefore, it is important to use caution when distinguishing the claimed invention from the prior art so as to focus only on those features necessary to patentability.  Knowing where such distinctions have been drawn and where they may have been avoided provides a map to both patentees and accused infringers considering possible equivalents arguments.