Certificate of Correction Changing a Chemical Structure Does Not Affect Validity of Patent

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Federal Circuit Review No. 75-3.

Certificate of Correction Changing a Chemical Structure Based on Later Discovery Not Invalid

Cubist Pharms., Inc. v. Hospira, Inc., No. 2015-1197, 2015-1204, 2015-1259, 2015 U.S. App. LEXIS 19662 (Fed. Cir. Nov. 12, 2015) (Before Wallach, Bryson, and Hughes, J.) (Opinion for the court, Bryson, J.).  Click Here for a copy of the opinion.

Hospira filed an ANDA application for permission to market a generic form of the antibiotic daptomycin.  Cubist sued Hospira, claiming infringement of five patents covering daptomycin. One patent covered the formulation of daptomycin, two covered dosage regimens for administering daptomycin, and two covered purification techniques for daptomycin compositions.  Following a bench trial, the district court found all claims of the dosage and purity patents invalid as anticipated or obvious, but two claims of the formulation patent valid and infringed. Both parties appealed the judgments against them.

Hospira appealed the finding of no invalidity and infringement of Cubist formulation patent. Hospira argued that a certificate of correction, which modified a figure depicting the chemical structure of daptomycin, was invalid, and that the patent with the original figure was not infringed.  Alternatively, Hospira argued that if the certificate of correction was properly granted, the claims were still invalid because there was no written description of daptomycin in the application as originally filed. 

The court rejected both arguments.  First, the certificate of correction was properly granted.  The sole modification in the figure amended was to change one of the 13 amino acids in the structure of daptomycin from an L-stereoisomer to a D-stereoisomer of asparagine. At the time of the invention, it was universally believed that daptomycin included the L-stereoisomer. Not until years later did Eli Lilly discover the error.  In any case, the certificate of correction did not affect the validity of the patent, because daptomycin had been described in numerous ways in the application, including by referencing another application that described how to make daptomycin, which would have inherently included the D-stereoisomer.  Thus, the certificate of correction was correctly issued, and the alternative descriptions of daptomycin showed that the inventors were in possession of daptomycin, satisfying the written description requirement.

Cubist appealed the findings of invalidity of the dosage patents. The court affirmed the district court’s findings of invalidity.  The dosage patents claimed a dose of 4 to 6 milligrams per kilogram of patient weight, administered every 24 or 48 hours. Hospira argued that the claims were invalid over a prior art journal article which described “doses of 4 to 6 mg/kg/day, possibly in divided doses.”  The only difference between the journal article and the dosage patents was that the dosage patents described a skeletal toxicity problem associated with frequent, smaller doses of daptomycin that was overcome by less frequent dosing. The journal article made no mention of skeletal toxicity, but was based on an observed long half-life of daptomycin. The court upheld the finding of invalidity of the dosage, holding that the article was enabling and taught the 24 hour embodiment.  Further, a person of ordinary skill would predict that someone with decreased kidney function may require a longer dosage interval – because of the long half-life – rendering the 48 hour claims obvious. The court further rejected Cubist’s arguments based on secondary indicia of non-obviousness, and held that recognition of the skeletal toxicity issue was irrelevant to its finding of obviousness.

Cubist further appealed the findings of invalidity for the purity patents. The court affirmed the district court’s findings of invalidity. There, the prior art taught that daptomycin forms micelles in an acidic solution. The claims of the patent merely taught the use of known filtration techniques for micelles, or aggregates, with no further added steps.  Accordingly, the claims were invalid as obvious, since a person of ordinary skill in the art equipped with the knowledge of daptomycin’s properties would have arrived at the claimed invention.