Parties may rely on extrinsic evidence when establishing a claim element’s function under the doctrine of equivalents

Intendis GMBH, et al. v. Glenmark Pharmaceuticals, Inc., et al., No. 2015-1902 (Fed. Cir. May 16, 2016)

In a Hatch-Waxman case, the district court held that the alleged infringer’s Abbreviated New Drug Application (ANDA) product, a topical gel for the treatment of rosacea, infringed the patent under the doctrine of equivalents. The Federal Circuit affirmed.

The district court held that the excipient in the alleged infringer’s product and the claimed excipients both functioned as penetration enhancers. On appeal, the alleged infringer argued that the district court erred in applying the function prong of the function-way-result test because the patent did not define the claimed excipients as penetration enhancers. The Federal Circuit rejected the argument that a claim element’s function must come from the intrinsic record. Instead, the appropriate test, which can be proven through extrinsic evidence, is what a person of ordinary skill in the art would understand the function of the claim element to be. They found no error in the district court's holding of infringement under the doctrine of equivalents in part because of the alleged infringer’s repeated statements to the FDA that the claimed excipients functioned as penetration enhancers that the Federal Circuit found would “tend to show that one of skill in the art would understand the claimed excipients to function as penetration enhancers.”

In addition, the alleged infringer argued that the scope of equivalency proposed by the patentee was too broad and would ensnare the prior art. The Federal Circuit disagreed. To determine whether the scope of equivalency would ensnare the prior art, a hypothetical claim including the actual claim and its equivalents are construed. The alleged infringed argued that the hypothetical claim would include any penetration enhancer. The court disagreed, noting that in determining that the prior art was not ensnared, the district court properly applied the appropriate hypothetical claim to be one that extends the actual claim to literally recite only the compound used in the accused product rather than any permeation enhancer.

Finally, the alleged infringer also argued that, under prosecution history estoppel, the patentee had disavowed compositions involving the allegedly infringing excipient. The district court found that the patentee’s amendment was made for the purposes of clarification only such that estoppel did not apply. The Federal Circuit affirmed, noting that rather than demonstrating “a clear and unmistakable surrender of subject matter,” the amendment merely altered the language of a dependent claim to conform with the well-known rule that a dependent claim can never be broader than the independent claim from which it depends.

A copy of the opinion can be found here ►