In affirming that a certificate of correction may properly be used to correct a later-discovered error in a chemical diagram, the U.S. Court of Appeals for the Federal Circuit looked to the teachings of the specification as a whole to determine that the certificate merely conformed the erroneous diagram to the rest of the specification and did not change the scope of the claims. Cubist Pharms., Inc. v. Hospira, Inc., Case Nos. 15-1197; -1204; -1259 (Fed. Cir., Nov. 12, 2015) (Bryson, J.).

The patent at issue relates to novel pharmaceutical formulations of daptomycin, a prior art antibiotic originally discovered by Eli Lilly in the 1980s. The specification and claims refer to daptomycin as “Formula 3,” and the specification describes the identity of Formula 3 in three different ways. First, the specification refers to the compound as an “A-21978C cyclic peptide” and cites to another U.S. patent as describing such peptides as the result of a very specific bacterial fermentation process. Second, the specification refers to the Formula 3 compound as “LY146032,” which was the internal code name used by Eli Lilly to refer to daptomycin. Third, the specification contained a diagram depicting the compound’s chemical structure.

It turned out that the structural diagram of the compound identified as Formula 3 and depicting daptomycin was inaccurate in one respect. The chemical diagram mistakenly labeled the amino acid asparagine as the “L” stereoisomer, rather than the “D” stereoisomer. At the time the patent was filed, it was universally believed that the daptomycin compound included the L-isomer of asparagine. Many years after the patent issued, however, researchers determined that the compound known as daptomycin actually contained the D-isomer, not the L-isomer. Cubist successfully obtained a certificate of correction from the U.S. Patent and Trademark Office (USPTO) that substituted the D-isomer for the L-isomer.

Hospira argued that the USPTO erred by issuing the certificate of correction, because the change in the structural diagram resulted in a broadening of the claims from the L-isomer compound to the D-isomer compound. Hospira noted that this difference was meaningful because, although daptomycin—which contains the D-isomer—is a very powerful antibiotic, the L-isomer version of the compound is a much less effective antibiotic.

The district court and Federal Circuit agreed that the certificate of correction was appropriately issued because it did not, as Hospira alleged, cause an alteration in claim scope. In particular, because the “specification as a whole” made clear that the compound being claimed as “Formula 3” was always intended to be the prior art compound daptomycin, “D-asparagine was covered both before and after correction.” As one example, the Court noted that the particular bacterial fermentation process cited in the patent is one that necessarily and inevitably results in daptomycin, not the L-isomer variant. Moreover, the Court noted that it was well known in the art that the Lilly code LY146032 referred to daptomycin, not the L-isomer variant. According to the Court, even though the patentee and the art in general were originally mistaken about the correct asparagine isomer in daptomycin, there was no mistake or doubt that the patentee did, in fact, intend to refer to daptomycin in the patent. For these reasons, the certificate merely served to “conform the structural diagram of Formula 3 to the compound described in the specification and covered by the claims.”

In a related argument, Hospira argued that the claims were invalid for lack of written description because the specification did not disclose the features or structure of daptomycin containing the D-isomer. The Court rejected this argument as well, again invoking the teachings of the specification as a whole. In particular, the Court noted that “Formula 3” in the claims clearly refers to daptomycin and that the specification describes “relevant identifying characteristics” that are sufficient to distinguish daptomycin from other compounds not falling within the scope of the claims. The Court concluded that a skilled person reading the specification would understand the inventors to be in possession of daptomycin, notwithstanding the error in the original structural diagram of Formula 3.