Here, the claim language require a particular impurity level but the court found that they could not simply apply to individual-batches since that is already taught by the prior art. “Such a construction would render the claims of the ’727 patent invalid in light of Medicines’ numerous pre-critical-date sales of ANGIOMAX® batches having Asp9 levels below 0.6 percent.” Rather, the requirement that “the batches have a maximum impurity level” limitation must be construed to require cross-batch consistency — which requires that all of the batches be produced with the “same compounding process.”

Looking to the specification, the court found that the patentee had stated its “development of a compounding process for formulating bivalirudin that consistently generates formulations having low levels of impurities is desirable” and later discussed “the compounding process . . . of the invention” . . . “and as prepared by the new process of the present invention.” When then further delving into the specification, it became clear that the compounding process discussed is the efficient mixing process.

The appellate court reversed the district court’s decision based upon its revised claim construction. The claims require “batches” of the active ingredient that “have a maximum impurity level.” The court construed that term to require a consistent process for making all the batches, and then looked to the specification to note that the patentee intended to use an “efficient mixing” process as that consistent process since that was the type of process described in the specification; And then finally zeroed-in on the “efficient mixing” process and required that it follow the particulars of “example 5” of the patent since that was the only detailed example given of efficient mixing. With that narrowed claim construction, non infringement was easy.