Plaintiffs Abbott Laboratories and Central Glass Company (collectively “Abbott”) appeal from a judgment of noninfringement of U.S. Patent No. 5,990,176 (“the '176 patent”) by the United States District Court for the Northern District of Illinois. Defendants Baxter Pharmaceutical Products, Inc. and Baxter Healthcare Corp. (collectively “Baxter”) cross-appeal the district court’s determination that the asserted claims are valid and its refusal to find unenforceability due to inequitable con
*1365
duct. This is our second hearing of this case; following our first, we reversed the district court’s claim construction and remanded for trial.
Abbott Labs. v. Baxter Pharm. Prods., Inc.,
Because we hold the asserted claims of the '176 patent to be anticipated by the disclosure in U.S. Patent No. 5,684,211 (“the '211 patent”), we reverse the district court’s validity judgment.
I. BACKGROUND
A. The technology
Sevoflurane is a fast-acting, highly effective inhalation anesthetic. However, pure sevoflurane has a serious problem, unknown at the time of its invention and original shipment: it degrades in the presence of Lewis acids. Lewis acids are essentially defined as any species with an empty electron orbit leading to electron affinity and are common enough that avoiding exposure of sevoflurane to Lewis acids is quite difficult. Among the products of the degradation reaction is hydrofluoric acid, which is highly dangerous if inhaled. '176 patent col.l 11.52-57. The original containers in which Abbott shipped its product had Lewis acids exposed on their interiors. The hydrofluoric acid thus produced etched the containers’ glass surfaces, exposing even more Lewis acids, resulting in a vicious-cycle cascading reaction that seriously compromised Abbott’s product while on the shelf and forced a recall.
After investigating the cause of the degradation, Abbott discovered the source of the problem. It also found a solution: 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: previously, Abbott had sought to minimize its product’s water content. 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 at issue here.
B. Prior proceedings
Baxter sought to ship its own sevoflu-rane product. On January 26, 2001, it filed an amended Abbreviated New Drug Application (“ANDA”) with the Food and Drug Administration (“FDA”) covering its own sevoflurane product. Baxter filed with the FDA a certification of nonin-fringement and invalidity of the '176 patent pursuant to 21 U.S.C. § 355(j)(2)(A)(vii)(IV) (commonly known as a “paragraph TV certification”), which created the cause of action giving rise to this suit under 35 U.S.C. § 271(e)(2).
There are multiple product and method claims at issue. Claim 1 of the '176 patent is representative:
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 hydroxy-toluene, methylparaben, propylparaben, propofol, and thymol.
’176 patent col. 11 11.21-29. The other claims at issue speak to using water specifically, methods of combining sevoflurane and Lewis acid inhibitors to produce the *1366 above-mentioned composition, or both. Id. at cols.11-12.
This case came before us for the first time when we reviewed the district court’s construction of the phrase “amount effective to prevent degradation” to require at least 131 parts per million (“ppm”) of water and its consequent summary judgment of noninfringement.
Abbott,
Baxter made two distinct invalidity arguments. It first argued that since some lots of the pre-recall sevoflurane sold by Abbott had not degraded, there had been a prior sale which would bar the patent. The district court found insufficient evidence that those lots had actually been exposed to Lewis acids, making a finding that they had contained water “in an amount effective to prevent degradation” unsupportable.
Id.
at 44. Baxter’s second argument was that the '211 patent disclosed a composition of water-saturated se-voflurane that met all the limitations of the asserted claims.
Id.
at 37-39. The district court noted some of our holdings finding anticipation even where, as here, there was no knowledge at the time of the relevant properties of the prior art.
Id.
at 40-41 (citing
Atlas Powder Co. v. IRECO, Inc.,
All of these rulings by the district court are before us via either Abbott’s appeal or Baxter’s cross-appeal. Abbott challenges the claim construction, arguing that the intrinsic evidence of the '176 patent permits more than 4,000 ppm of impurities before the sevoflurane may be considered “degraded.” Abbott also challenges the district court’s findings on literal and doctrine of equivalents infringement. Baxter challenges enforceability and validity, the latter in light of both the '211 patent and *1367 the alleged prior sale. We have jurisdiction pursuant to 28 U.S.C. § 1295(a)(1).
II. DISCUSSION
A. Standard ofrevieiu
Patent claims are presumed to be valid, 35 U.S.C. § 282, and the party seeking to show invalidity must prove facts supporting invalidity by clear and convincing evidence.
N. Am. Vaccine, Inc. v. Am. Cyanamid Co., 7
F.3d 1571, 1579 (Fed.Cir.1993). Since this case comes to us from a trial without jury, we review the district court’s findings of fact for clear error and its legal conclusions de novo.
Panduit Corp. v. Dennison Mfg. Co.,
B. The '211 patent
The '211 patent was applied for in 1995 and awarded to Kawai et al. in November 1997. Appellant Central Glass Co. is the assignee. The parties do not dispute that the '211 patent predates the '176 patent for the purposes of 35 U.S.C. § 102, and the facts about what the '211 patent teaches are in relevant part undisputed. It discloses a technique for purifying sevoflurane for “use[] as a pharmaceutical and particularly as an inhalation anesthetic,” '211 patent abstract, which involves the addition of water. If the steps of its Illustration 1, Table 2 are practiced, the result will be sevoflurane that is saturated with water, unable to absorb any more moisture. Saturation implies that the sevoflurane contains an amount of water sufficient to prevent it from degrading due to Lewis acids.
At the time, however, knowledge of the beneficial nature of a water-sevoflurane mix was wholly lacking in the art. The district court describes the matter succinctly:
[Pjrior to [the '176 patent] invention no one had any idea that Lewis acids had the potential to degrade sevoflurane. Further, no one was aware of the stabilizing effect water would have to prevent Lewis acid degradation. In fact, water was considered an impurity and was removed from sevoflurane to the extent possible during the manufacturing process that included the teachings of the '211 patent.
Abbott,
No. 01-CV-1867, slip op. at 39,
C.Unknoum properties and anticipation
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,
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,
Abbott’s objection here is merely that at the time of the '211 patent, nobody knew that the water-saturated sevoflurane that patent disclosed had the property of resisting the Lewis acid degradation reaction. Just as in Titanium Metals, that lack of knowledge is wholly irrelevant to the question of whether the '176 patent claims something “new” over the disclosure of the '211 patent; the claimed property of resistance to degradation is found inherently in the disclosure. Since the '211 patent discloses sevoflurane saturated with water— i.e., unable to absorb any additional water to further protect it from the degradation reaction — it anticipates the claims of the '176 patent. This is true under any definition of the term “prevent degradation” that the claims might reasonably bear, so we need not construe that phrase with numerical exactitude in order to reach our decision.
The district court nonetheless found the patent valid due to the purpose-based distinction we drew in
Bristol-Myers Squibb. Abbott,
No. 01-CV-1867, slip op. at 42-43 (citing
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 sevoflu-rane. 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.
III. CONCLUSION
For the reasons given above, we reverse the district court’s judgment that the asserted claims of the '176 patent are valid. Since all asserted claims are invalid, we do not reach questions of infringement or inequitable conduct.
REVERSED.
No costs.
