Nobel laureate Frank Wilczek said, “If you don’t make mistakes, you’re not working on hard enough problems. And that’s a big mistake.” Because inventions often address difficult problems on the forefront of technology, some mistakes are inevitable. For mistakes of “minor character,” patentees can request that the USPTO issue a certificate of correction to address such errors.

In Cubist Pharmaceutical v. Hospira, the Federal Circuit recently addressed the acceptability of using a certificate of correction to correct an inaccurate chemical structure in an issued patent. The patent concerned antibiotic compositions containing daptomycin. The patent disclosed a structural diagram of the daptomycin molecule, as Formula 3, that contained 13 amino acids. The structural diagram accurately identified each of the amino acids and their location in the molecule, but mistakenly identified the stereoisomer of a single asparagine amino acid as the “L” stereoisomer rather than the “D” stereoisomer.

Researchers discovered the error in the chemical structure several years after the patent issued. To correct the error, the patent owner requested that the USPTO issue a certificate of correction. In its request, the patent owner explained that the true nature of the stereochemistry of daptomycin was recognized after the patent issued, and that the patent merely mischaracterized the structure. Thus, the patent owner reasoned that the correct “D” stereoisomer was inherently present in the original patent application. The Examiner agreed that it was appropriate to correct the error in the structural diagram, and issued the certificate of correction.

During subsequent litigation, the defendant argued that the certificate of correction issued in error because the change in the structural diagram of daptomycin altered the substance of the claims and broadened their scope. The defendant also took the position that the claims should be limited to the variant of the daptomycin compound containing the L-isomer of asparagine, which was found to have reduced potency as compared to the D-isomer. Consequently, the defendant argued that the certificate of correction was not a change of “minor character.”

The Federal Circuit found that the defendant failed to establish that the certificate was improperly issued. To invalidate a certificate of correction, clear and convincing evidence must establish that the certificate was improperly issued. However, the showing presented by the defendant was insufficient to meet this burden.

Specifically, the Federal Circuit recognized that a chemical structure is simply a means of describing a compound – not the invention itself. The meaning of patent claims, therefore, should not simply be limited to the chemical structure depicted in the diagram, but rather assessed based upon the entire specification. In the specification, daptomycin was not discussed only in terms of its structural diagram, but rather the specification taught that the daptomycin is obtained through fermentation of Streptomyces roseosporus, which necessarily results in daptomycin with the D-isomer of asparagine and not the variant with the L-isomer of asparagine. The specification similarly suggested that the L-isomer variant cannot be produced by fermentation, but can only be produced synthetically. Accordingly, even though researchers recognize the correct chemical structure well after the patent issued, the Federal Circuit found that the specification was clearly directed to daptomycin having the D-isomer of asparagine.

Additionally, the defendant argued that, if the certificate of correction was found to be properly issued, the claims of the patent must violate the written description requirement of 35 U.S.C. § 112. The Federal Circuit rejected this argument and found that, notwithstanding the error in the structural diagram, one skilled in the art would have understood that the inventors possessed and were working with the naturally occurring fermentation product (i.e., the daptomycin molecule containing D-asparagine). The mere fact that the inventors were mistaken as to one aspect of the structure of daptomycin, therefore, did not render the specification inadequate to satisfy the written description requirement.

For these reasons, inter alia, the Federal Circuit found that the certificate of correction was properly issued and that the patent was otherwise valid. Based upon the decision of the Federal Circuit, patent owners may wish to consider correcting later-discovered errors in chemical structures with a certificate of correction. However, a careful analysis of the specification and the state of the art should be performed to establish whether the inventors actually possessed the correct chemical compounds at the time of filing the application, and whether the mistake can be consider one of “minor character.”

Wenderoth, Lind & Ponack, L.L.P.

1030 15th Street, N.W.

Suite 400 East

Washington, D.C. 20005 USA

T: (202) 721-8200

F: (202) 721-8250

E: wlp@wenderoth.com