Are claims that recite a “solvate” of a chemical compound invalid for lack of written description if the patent does not describe any specific solvates? In GlaxoSmithKline LLC v. Banner Pharmacaps, Inc., the Federal Circuit said No, and upheld the district court’s determination that the defendants had not proven that the claims were invalid.

The Patent at Issue

The patent at issue was GSK’s U.S. Patent 5,565,467, which claims

17ß-N-(2,5- bis(Trifluoromethyl))phenylcarbamoyl-4-aza-5a-androst-1-en-3-one or a pharmaceutically acceptable solvate thereof.

The claimed compound also is known as dutasteride.

The defendants had sought FDA approval of generic versions of GSK’s Avodart® and/or Jalyn™ products, which contain dutasteride and are approved for the treatment of benign prostatic hyperplasia. Thus, the underlying patent litigation was ANDA litigation brought pursuant to 35 USC § 271(e)(2).


As summarized in the Federal Circuit opinion, the district court construed “solvate” of dutasteride to mean

A complex formed by dutasteride with a solvent in which dutasteride is reacted or from which it is precipitated or crystallized.

The parties agreed that the district court’s claims construction encompasses three ways 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;
  • by crystallization of a complex from a solution of dutasteride and a solvent

They also agreed that the district court’s claims construction does not require the resulting complex to be crystalline.

The defendants stipulated to infringement under that claim construction, but challenged the patent’s validity.

The Federal Circuit Decision

The Federal Circuit decision was authored by Judge Taranto and joined by Judges O’Malley and Wallach.

The Federal Circuit determined that whether or not the term “solvate” required a crystalline structure, the written description requirement was satisfied. In particular, the Federal Circuit noted that the patent “provides a description by structure and process of creation that matches the claimed term, whichever construction is preferable,” citing this passage from the patent:

Those skilled in the art of organic chemistry will appreciate that many organic compounds can form complexes with solvents in which they are reacted or from which they are precipitated or crystallized. These complexes are known as “solvates”. For example, a complex with water is known as a “hydrate”. Solvates of [dutasteride] are within the scope of the invention. It will also be appreciated by those skilled in organic chemistry that many organic compounds can exist in more than one crystalline form. For example, crystalline form may vary from solvate to solvate. Thus, all crystalline forms of [dutasteride] or the pharmaceutically acceptable solvates thereof are within the scope of the present invention.

The Federal Circuit determined that the patent “defines the claimed genus by two properties”:

  1. Structurally, as being “a complex of dutasteride molecules and solvent molecules” and
  2. By the process(es) by which it is made.

The court concluded:

[T]he description remains entirely based on structure of the compound and its process of creation. We have no precedent under which this two-condition description, matching the claim scope, would be insufficient.

In reaching its conclusion, the Federal Circuit noted that the claims do not involve “functional claim language,” and that the defendants had not raised any issues surrounding the “pharmaceutically acceptable” language. Thus, the Federal Circuit affirmed the district court’s finding that the defendants had failed to establish invalidity for lack of written description.

Structure Versus Function

As noted above, the Federal Circuit found it significant that the claims at issue did not recite any functional terms, which can render claims vulnerable to written description challenge. This preference for structure versus function in the written description context is not new, but serves as a good reminder to focus on structural language when possible, and be careful when introducing functional language into the claims. The Federal Circuit’s comments about the “pharmaceutically acceptable” language is an interesting one. Could the defendants have raised a successful written description challenge on the basis that the patent does not describe any specific pharmaceutically acceptable solvates of dutasteride?