The Federal Circuit recently upheld a district court’s determination that claims directed to preparing stable phenol formulations were infringed under the doctrine of equivalents. One of the asserted patents (the “’218 Patent”) covered a method for obtaining stable acetaminophen formulations by deoxygenating solutions with an inert gas to achieve oxygen concentrations below 2 parts-per-million (ppm). The plaintiff alleged that defendant’s generic equivalent of its injectable acetaminophen product, Ofirmev®, infringed claims of the ‘218 Patent either literally or under the doctrine of equivalents. The district court found that the accused process, which first deoxygenates a solvent and only then adds an active ingredient, did not literally infringe. Nevertheless, the court held that the accused process infringed under the doctrine of equivalents (DOE). In reaching its decision, the court found that the timing of the addition of the active ingredient did not matter and ruled that the differences between the claimed steps and accused method were insubstantial. In affirming the district court’s ruling, the Federal Circuit (the “court”) credited expert testimony explaining “that adding acetaminophen before or after the deoxygenation step would have no impact on the stability of the final product.” The court found that this testimony supported the district court’s finding that changing the timing of the deoxygenation step was an insubstantial difference.

The court also rejected the defendant’s contention that deoxygenating after adding the active ingredient is the “antithesis” of deoxygenating before adding the active ingredient and that because such a substitution would “vitiate” the claimed limitation, there can be no finding of equivalence. The court explained that “‘[v]itiation’ is not an exception or threshold determination that forecloses resort to the doctrine of equivalents, but is instead a legal conclusion of a lack of equivalence based on the evidence presented and the theory of equivalence asserted.” Because there was no evidence that the accused process is substantially different from the recited claims, the court held that “the argument that a claim limitation is vitiated by the district court’s application of the doctrine of equivalents is both incorrect and inapt.”

Cadence Pharma. Inc., v. Exela Pharmsci Inc., 2014-1184 (Fed. Cir. 2015).