A recent Federal Circuit case shows that broad, functionally-defined genus claims are susceptible to written-description invalidity challenges.  In AbbVie Deutschland GmbH & Co. v. Janssen Biotech, Inc. et al., the Federal Circuit affirmed a jury verdict invalidating a patent, finding that there was substantial evidence to conclude that the claims failed to meet the Patent Act’s written description requirement.

AbbVie sued Centocor for infringing AbbVie’s patents claiming human antibodies that bind to and neutralize a type of human interleukin, IL-12, the overproduction of which can cause psoriasis and rheumatoid arthritis.  The patents disclosed sequences of about 300 such antibodies, which all share 90% or more amino acid sequence similarity, and more than 200 of which differ by only one amino acid.  The patent claims defined the claimed antibodies by binding affinity to IL-12, rather than by structure.  Centocor’s antibodies, while falling within the functional limits of the claims, differed significantly from the structure of the exemplary antibodies of the patents.

At trial, Centocor relied on lack of written description among other invalidity defenses.  It was undisputed that the patents did not disclose structural features common to various members of the claimed genus, as AbbVie’s expert conceded.  Thus, the question at issue was whether the patents sufficiently described representative species in some other way to support the entire claimed genus.  The jury, hearing ample evidence that AbbVie’s patents described only one type of structurally similar antibodies, answered that question in the negative in returning a verdict for Centocor.

On appeal, the Federal Circuit, with Judge Lourie writing, agreed that there was substantial evidence to affirm that finding.  In rejecting AbbVie’s argument that the structural differences of the antibodies was irrelevant because the claims were defined by function, the Federal Circuit noted that the claimed range of binding affinity was merely a desired result, rather than the actual means for achieving the result.  The Court noted that functionally defined claims can meet the written description requirement if there is a reasonable structure-function relationship correlation established, whether as shown by the inventor in the specification or known in the art.  Such a correlation was lacking here.

Broad function-based limitations are often at issue in generic pharmaceutical patent infringement cases.  This case provides a cautionary example for the enforcement of broad functional claims where the specification lacks examples commensurate in structural scope with the broad claims, at least in the absence of a proven structure-function relationship correlation.