The Federal Circuit recently affirmed the District of Delaware’s rejection of a lack of written description defense in GlaxoSmithKline LLC v. Banner Pharmacaps, Inc., No. 2013-1593 (Fed. Cir. 2014).  GlaxoSmithKline sued several generic companies for infringement of U.S. Patent No. 5,565,467, which is listed in the Orange Book for Avodart (dutasteride), a treatment for enlarged prostate.

The ‘457 patent covers dutasteride and its pharmaceutically acceptable solvates.  The defendants stipulated to infringement but asserted several invalidity defenses, including inadequate written description under 35 U.S.C. § 112(a).  After a bench trial in the District of Delaware, Judge Richard G. Andrews found that the defendants did not prove that the claims were invalid.  The defendants appealed the rejection of the written description defense that the term “solvate” was not adequately described.

The written description requirement of section 112(a) requires that the written description clearly allows persons of ordinary skill in the art to recognize that the inventor invented what is claimed.  The test is whether the disclosure reasonably conveys to those skilled in the art that the inventor had possession of the claimed subject matter as of the filing date.

The District of Delaware construed a “solvate” of dutasteride to mean “a complex formed by dutaseride with a solvent in which dutasteride is reacted or from which it is precipitated or crystallized.”  The parties agreed that the construction referred to three processes of forming dutasteride solvates — by a reaction of dutasteride with a solvent; by precipitation of a complex from a solution of dutasteride and a solvent; and by crystallization of a complex from a solution of dutasteride and a solvent.  The defendants argued that the written description failed to describe the range of solvates encompassed by that construction.

After criticizing the briefing of the defendants, the Federal Circuit reviewed the District Court’s holding for clear error and agreed that the term “solvate” refers to a molecular complex defined by structure and the process of creating it.  The Court further agreed that the term was adequately described in the specification because the description was entirely based on the structure of the compound and its process of creation, allowing one of skill in the art to visualize or recognize the members of the claimed genus of “solvates.”

The Court distinguished these facts from other cases in which the claim term was functional, such as a performance property of encoding a particular enzyme or other product or ability to inhibit the action of a particular protein or medical complication or an antibody’s ability to bind a particular antigen.  In this case, the “solvates” were not distinguished by such a performance property.

Thus, generic defendants should take care to carefully vet a potential written description defense where the claims do not include functional claim language.