A certificate of correction may be used to correct the chemical structure of a claimed compound based on later discoveries when the specification as a whole makes clear that the patentee nevertheless possessed the compound at the time of filing. Here, for example, the correction of a structural diagram in the drawings to reflect a new understanding of which isomers were utilized by a claimed compound was found to be appropriate because the specification described the claim compound elsewhere in more general terms, including its synthesis route and code number. “[A] chemical structure is simply a means of describing a compound; it is not the invention itself.” This would be a good case to consult before requesting a certificate of correction from the PTO based on a scientific error.
Background / Facts: The patent being asserted here in response to a generic drug ANDA submission is directed to the antibiotic daptomycin. The specification describes daptomycin in several ways, including by its synthesis route, its code name, and a chemical formula whose structure is illustrated in the figures. It turns out that the structural diagram depicting daptomycin was inaccurate in one respect. At the time the application was filed, and until well after the patent issued, it was universally believed that the asparagine amino acid in daptomycin was the L-isomer of asparagine, as set forth in the structural diagram. Years later, however, researchers discovered that daptomycin actually contains the D-isomer of asparagine, not the L-isomer.
Issue(s): Whether the PTO erred by issuing a subsequent certificate of correction to address this error in that the change in the structural diagram altered the substance of the claims, broadening their reach.
Holding(s): No. “The specification of the [] patent does not rely exclusively on the structural diagram of Formula 3 to describe the subject compound. … [T]he specification teaches that daptomycin is obtained through fermentation of Streptomyces roseosporus … [which] necessarily results in daptomycin, not the variant with the L-isomer of asparagine. … In addition, the specification describes the claimed compound by the code name given to it. … Even though researchers had previously been mistaken about the precise chemical structure of daptomycin, it was nonetheless clear from the specification that the patentees possessed daptomycin (with the D-isomer of asparagine) and that the references to Formula 3 in the claims of the [] patent were directed to daptomycin.”