In a unanimous panel decision, the Federal Circuit found that Hanmi Pharmaceutical Co. Ltd.’s esomeprazole (Nexium®) does not infringe two AstraZeneca patents listed in the Orange Book for its Nexium® product.  AtraZeneca v. Hanmi Pharmaceuticals, No. 13-1490, 2013 U.S. App. LEXIS 25199, (Dec. 19, 2013).  AstraZeneca appealed Judge Pisano’s finding from the United States District of New Jersey (No. 13-1490) that the claim term “alkaline salt” only encompassed the 6 cations explicitly disclosed in the patent.  Hanmi uses a different cation than the six disclosed in AstraZeneca’s patent, and as a result, Judge Pisano found that Hanmi’s product did not infringe.

AstraZeneca advanced three arguments appealing the finding.  First, AstraZeneca argued that one passage from the written description showed that the six cations identified were just examples of a broader group.  The passage from U.S. Patent No. 5,714,504 reads “Alkaline salts of the single enantiomers of the invention are, as mentioned above, beside the sodium salts (compounds Ia and Ib) and magnesium salts (compounds IIa and IIb), exemplified by their salts with Li, K, Ca, and N(R)₄, where R is an alkyl with 1-4 C-atoms.”  The Court rejected this argument because (1) it was not clear that the “exemplified” language directly applied to only four of the six cations; (2) the language “is not preceded by the word ‘also’ or any other language that might have more affirmatively suggested an intent to treat all six identified cations as merely exemplary.”

Second, AstraZeneca argued that a statement made in the prosecution history showed intent to broaden the genus of alkaline salts.  The statement read “…the full scope of the genus of alkaline salts disclosed in the application and as claimed herein.”  But the Court disagreed for the following reasons: (1) the prosecution history lacked any mention of any salt beyond the six identified in the patent; (2) the term “genus” could refer simply to an enumerated collection similar to a Markush-type claim; (3) the reference to “genus of alkaline salts disclosed in the application and as claimed herein” limited the genus to the particular salts disclosed.

Finally, AstraZeneca argued that doctrine of claim differentiation suggests a broader genus because each independent claim reciting an “alkaline salt” has a dependent claim that adds the 6 identified cations.  But the Court also rejected this argument finding that claim differentiation cannot override the “unmistakable limitation of ‘alkaline salt’” set out in the written description.

Thus, because the written description of the patent contained a clear disclaimer of claim scope, and no aspect of the intrinsic record suggested otherwise, the Court affirmed the district court’s construction, and consequently the judgment of noninfringement.  The decision should serve as a reminder about the importance of drafting the written description as broadly as possible to prevent inadvertent limitations on claim scope.