Amgen, Inc. v. Amneal Pharmas. LLC et al. (Fed. Cir. Jan. 7, 2020)

Where a claim has a preamble with the transitional phrase "comprising" and recites two Markush groups reciting “at least one [binder/disintegrant] selected from the group consisting of …,” an infringing composition may include other binder/disintegrant compounds as long as one element in each Markush group is present. Also, an Examiner's Amendment that proposed adding Markush groups and resulted in an allowance creates a presumption of prosecution history estoppel that bars use of the doctrine of equivalents.

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