The US Court of Appeals for the Federal Circuit affirmed the finding of infringement from the US District Court for the District of Delaware under the doctrine of equivalents based on admissions from the defendant’s abbreviated new drug application (ANDA). Intendis GMBH v. Glenmark Pharmaceuticals Inc., USA, 822 F.3d 1355 (2015) (Moore, C.J.)

At issue was whether Glenmark’s design-around formulation infringed Intendis’ Orange Book-listed formulation patent (US No. 6,534,070) for Finacea® Gel (azelaic acid) under the doctrine of equivalents. The patent claims required the presence of at least one triglyceride and lecithin in the azelaic acid formulation. The issue was whether isopropyl myristate in Glenmark’s generic product performed the same function as the two required excipients under the doctrine of equivalents. The district court found equivalency under the function-way-result test, relying on expert testimony, support in the scientific literature and statements in Glemark’s ANDA and patent application.

Glenmark argued on appeal that (1) Intendis failed to prove the claimed excipients functioned as penetration enhancers because the ‘070 patent did not disclose this function, and (2) that the district court erred in finding isopropyl myristate functioned as a penetration enhancer in Glenmark’s formulation. Even though the ‘070 patent did not disclose that triglycerides and lecithin function as penetration enhancers, the Federal Circuit noted that it has “never held that a patent must spell out a claim element’s function, way, and result in order for the doctrine of equivalents to apply as to that element.” Rather, “when the claims and specification of a patent are silent as to the result of a claim limitation,” courts should “turn to the ordinary skilled artisan.” Thus, fact finders may rely on extrinsic evidence to determine how a claim element functions. Here, the key extrinsic evidence was Glenmark’s statements in its own ANDA submission that repeatedly referred to the excipients in question as penetration enhancers.

The Federal Circuit also affirmed the district court’s hypothetical claim analysis on whether the equivalents would impermissibly ensnare the prior art. The court determined the hypothetical claim adopted by the district court was proper in scope, rejecting Glenmark’s argument that the hypothetical claim must capture all penetration enhancers, not just isopropyl myristate.

Finally, the Federal Circuit found no error in the district court’s finding that prosecution history estoppel did not bar the application of the doctrine of equivalents to the claim elements in question. The amendment in question concerned revision of lecithin concentrations in two dependent claims from the range of “up to 1%” and “up to 3%” to “from more than 0 to 1%” and “from more than 0 to 3%.” These claims depended from independent claims that required lecithin. Reasoning that dependent claims can never be broader than the independent claim from which they depend, the dependent claims as originally written could not have included zero percent lecithin formulations, and thus patentees did not disclaim lecithin-free formulations.