The US Court of Appeals for the Federal Circuit affirmed a rare grant of preliminary injunction based on one of three patents in suit, but reversed the injunction as to the other two patents based on the district court’s improper analysis of the doctrine of equivalents under the function-way-result (FWR) test. Mylan Institutional LLC v. Aurobindo Pharma Ltd., Case No. 17-1645 (Fed. Cir., May 19, 2017) (Lourie, J).

Apicore owns, and Mylan is the exclusive licensee of, the patents at issue, which relate to ISB, a triarylmethane dye used to map lymph nodes. Two of the three patents are directed to a process for preparing ISB by reacting isoleuco acid with silver oxide in a polar solvent, followed by reaction with a sodium solution (process patents). The third patent is directed to an ISB compound having a purity greater than 99.0 percent as measured by high-performance liquid chromatography (purity patent). Aurobindo sought US Food and Drug Administration approval for a generic 1 percent injectable solution of ISB after studying a number of patents describing ISB manufacture and selecting Apicore’s process patent.

Mylan sued Aurobindo for infringement and sought a preliminary injunction, which the district court granted after analyzing the four factors. The district court concluded that Aurobindo “more likely than not” infringed the process patents under the doctrine of equivalents. Specifically, the district court found that the difference in oxidation strength between silver oxide and manganese dioxide was irrelevant under both the FWR and the insubstantial differences tests for equivalence because the claims did not specify an oxidation strength requirement. Aurobindo appealed the district court’s holdings regarding infringement, as well as its holding that Aurobindo did not raise a substantial question as to validity of the purity patent and regarding irreparable harm to Apicore.

As to the process patents, the Federal Circuit concluded that the district court’s analysis of equivalence was flawed “no doubt because of the sparse and confusing case law concerning equivalents, particularly the paucity of chemical equivalence case law, and the difficulty of applying the legal concepts to the facts.” The Court explained that the FWR test may not be well suited for chemical cases (noting the same observation by the Supreme Court of the United States in Warner-Jenkinson) because the “function” and “way” of a particular limitation of a chemical process claim often overlap. Here, the district court did not consider the “way” the oxidation works because while manganese dioxide and silver oxide may have the same function, there was room for sufficient doubt as to whether they oxidize isoleuco acid in the same way so as to satisfy the “way” prong of the FWR test. The Federal Circuit noted that the district court may wish to consider whether the insubstantial differences test is more applicable in this case, because the “FWR test may be less appropriate for evaluating equivalence in chemical compounds if it cannot capture substantial differences between a claimed and accused compound.”

Turning to the purity patent, the Federal Circuit affirmed the district court’s grant of the preliminary injunction premised on this patent. In so doing, the Federal Circuit found that the district court did not err in finding irreparable harm, and that Aurobindo did not raise a substantial question concerning the validity of the patent.