The U.S. Court of Appeals for the Federal Circuit again hammers home the message that you can’t make a silk purse from a sow’s ear – or, at the very least, you can’t turn a known compound into an unknown (novel and, therefore, patentable) compound.

In Abbott Laboratories v. Baxter Pharmaceutical Products (Fed. Cir. 06-1021, -1022, -1034; Nov. 9, 2006), the CAFC held that Abbott’s asserted claims on the formulation of an inhaled anesthetic called sevoflurane, U.S. Patent No. 5,990,176, were anticipated by the disclosure in U.S. Patent No. 5,684,211.

Claim 1 of the ’176 patent reads:

An anesthetic composition comprising: a quantity of sevoflurane; and a Lewis acid inhibitor in an amount effective to prevent degradation by a Lewis acid of said quantity of sevoflurane, said Lewis acid inhibitor selected from the group consisting of water, butylated hydroxytoluene, methylparaben, propylparaben, propofol, and thymol.

Sevoflurane is an inhalation anesthetic. However, pure sevoflurane degrades in the presence of Lewis acids (a substance that can accept an electron pair from a base). Among the products of the degradation reaction is hydrofluoric acid, which is highly dangerous if inhaled.

Abbott found that water mixed in with sevoflurane will bind to and deactivate Lewis acids, protecting the sevoflurane from the degradation reaction. A deliberate addition of water to sevoflurane ran counter to the conventional wisdom at the time. Abbott filed a patent application on the degradation-preventing combination of water or other “Lewis acid inhibitors” with sevoflurane, which issued as the ’176 patent.

Baxter filed with the FDA a certification of noninfringement and invalidity of the ’176 patent pursuant to 21 U.S.C. § 355(j)(2)(A)(vii)(IV) (commonly known as a “paragraph IV certification”), which caused Abbott to sue under 35 U.S.C. § 271(e)(2).

Earlier, the district court construed of the phrase “amount effective to prevent degradation” to require at least 131 parts per million (“ppm”) of water in its consequent summary judgment of noninfringement. The CAFC disagreed with that construction, noting that “an effective amount of any given Lewis acid inhibitor will vary according to the conditions to which sevoflurane is subjected,” making construction referencing particular ranges of water content inappropriate. The CAFC then vacated the district court’s summary judgment and remanded.

On remand, the district court determined that the term “to prevent degradation” had been left unconstrued and concluded that “sevoflurane is degraded if it contains degradants in amounts greater than 300 ppm.” Baxter then appealed arguing that the ’211 patent disclosed a composition of water-saturated sevoflurane that met all the limitations of the asserted claims.

The CAFC agreed holding:

Our cases have consistently held that a reference may anticipate even when the relevant properties of the thing disclosed were not appreciated at the time. The classic case on this point is Titanium Metals Corp. v. Banner, 778 F.2d 775 (Fed. Cir. 1985). In Titanium Metals, the applicants sought patent protection on an alloy with previously unknown corrosion resistance and workability properties. Id. at 776. The prior art reference was an article by two Russian scientists that disclosed in a few data points on its graphs an alloy falling within the scope of the claims of the patent in suit. Id. at 776-77. There was no sign that the Russian authors or anyone else had understood the later-discovered features of the alloy thus described. Id. at 780-81. Despite the fact that “the applicants for patent had discovered or invented and disclosed knowledge which is not to be found in the reference,” we held that the Russian article anticipated the asserted patent claims. Id. at 782.

The general principle that a newly-discovered property of the prior art cannot support a patent on that same art is not avoided if the patentee explicitly claims that property. “[A] prior art reference may anticipate without disclosing a feature of the claimed invention if that missing characteristic is necessarily present, or inherent, in the single anticipating reference.” Schering, 339 F.3d at 1377 (citing Continental Can Co. v. Monsanto Co., 948 F.2d 1264, 1268 (Fed. Cir. 1991)). “[I]nherent anticipation does not require that a person of ordinary skill in the art at the time would have recognized the inherent disclosure.” Id. (citing Cruciferous Sprout, 301 F.3d at 1351).

The district court noted CAFC holdings finding anticipation even where, as here, there was no knowledge at the time of the relevant properties of the prior art. However, it concluded that the ’211 patent did not anticipate since the ’211 patent disclosed an “intermediate step” in the manufacture of sevoflurane, “the patent’s purpose was not to produce sevoflurane in its final useable form,” in distinction to the purpose of the ’176 patent, which “involves a final step in production.” At the time, however, knowledge of the beneficial nature of a water-sevoflurane mix was wholly lacking in the art.

The CAFC didn’t buy it stating that:

We also do not find it material that the district court found the anticipating method in the ’211 patent to be “an intermediate step” in the manufacture of sevoflurane. Abbott, No. 01-CV-1867, slip op. at 42. The product of that method was an anesthetic sevoflurane composition with sufficient water to prevent Lewis acid degradation—exactly what is claimed by the ’176 patent. Commercial finality is not claimed.

This really won’t have a market impact since Baxter already started selling its generic version of the anesthetic.

Update: IPBiz points out the CAFC’s curious definition of a Lewis acid.

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