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On January 6, 2003, a three-judge panel of the United States Court of Appeals for the Federal Circuit issued its opinion in Amgen Inc. v. Hoechst Marion Roussel, Inc., Nos. 01-1191, 01-1218, 2003 U.S. App. LEXIS 118 (Fed. Cir. Jan. 6, 2003), a patent infringement case involving EPOGEN -- a drug used to treat anemia in patients with chronic kidney failure. While also addressing the doctrine of equivalents, the reverse doctrine of equivalents, and several claim construction principles, the Court provided two significant holdings. First, the Court, in a 2-to-1 decision, clarified the requirements for written descriptions of certain biological materials, thereby distinguishing its previous holdings in Regents of the University of California v. Eli Lilly & Co., 119 F.3d 1559 (Fed. Cir. 1997) ("Eli Lilly") and Enzo Biochem, Inc. v. Gen-Probe, Inc., 296 F.3d 1316 (Fed. Cir. 2002) ("Enzo II"). Second, in the context of a validity challenge under section 102(a), the Court unanimously held that there is a rebuttable presumption of enablement for both claimed and unclaimed disclosures in prior art patents.

Background

Erythropoietin ("EPO") "is a naturally occurring protein that initiates and controls erythropoiesis, the production of red blood cells in bone marrow." Amgen Inc., 2003 U.S. App. LEXIS 118, at *6. Patients with chronic kidney failure lack normal levels of EPO and, as a result, have a sub-optimal number of red blood cells. This condition, known as anemia, can be treated by introducing additional EPO into the patient's system in order to increase the patient's ratio of red blood cells to total blood volume.

Through the use of recombinant EPO techniques, Amgen scientists were able to produce human EPO by introducing exogenous DNA into a number of different mammalian and vertebrate host cells. As a result of this research, Amgen secured patents covering the EPO produced by mammalian and vertebrate host cells as well as several methods for producing it. In April 1997, Amgen sued Hoechst Marion Roussel, Inc. and Transkaryotic Therapies, Inc. (collectively "TKT"), alleging that TKT infringed a number of Amgen's patents through its development of a competitive EPO product. TKT produced its EPO product, Gene-Activated EPO, utilizing endogenous, as opposed to exogenous, DNA.

In its decision, the district court made a number of findings including that the claims of three Amgen patents were valid and infringed by TKT. On appeal, TKT challenged the district court's construction of the claims and alternatively argued that, as broadly construed by the district court, such claims were invalid. As part of its invalidity defense, TKT claimed that Amgen's patents were invalid under section 112 for failure to adequately describe the claimed invention and enable its reproduction, and section 102(a) for being anticipated by a prior art patent (the "Sugimoto patent").

The Federal Circuit

After affirming the district court's construction of the claims asserted by Amgen, the Federal Circuit addressed TKT's two section 112 arguments. First, TKT argued that Amgen's general reference to the "mammalian" and "vertebrate" cells, which Amgen utilized to produce human EPO through recombinant DNA techniques, was insufficient to satisfy the written description requirement for biological materials articulated in Eli Lilly and Enzo II. The Federal Circuit held in Eli Lilly that "an adequate written description of a DNA requires more than a mere statement that it is part of the invention and reference to a potential method for isolating it; what is required is a description of the DNA itself." Eli Lilly, 119 F.3d at 1566-67. In Enzo II, the Federal Circuit clarified that while not "all functional descriptions of genetic material fail to meet the written description requirement," the functional description must be "coupled with a disclosed correlation between that function and a structure that is sufficiently known or disclosed." Enzo II, 296 F.3d at 1324.

The Federal Circuit, however, agreed with the district court and distinguished both Eli Lilly and Enzo II. The Court explained that the terms recited in Amgen's claims, unlike those in Eli Lilly and Enzo II, were "not new or unknown biological materials that ordinarily skilled artisans would easily miscomprehend." Amgen Inc., 2003 U.S. App. LEXIS 118, at *41. Instead, Amgen's patents merely referred to types of commonly known cells that can be utilized to produce human EPO as opposed to "undescribed, previously unknown DNA sequences." Id. at **41-42. The Court reasoned that, based on the district court's record, the terms "mammalian" and "vertebrate" readily identify their genus to one of ordinary skill in the art and, thereby, satisfactorily described the claimed invention.

Second, TKT argued that Amgen failed to enable the reproduction of its claimed invention by not describing all the methods to produce human EPO using recombinant DNA as well as not disclosing all the types of cells that could be used to practice its claimed invention. In upholding the lower court's rejection of these arguments, the Federal Circuit first noted that the claims challenged by TKT were either products or compositions -- not processes. Upon making this distinction, the Court reasoned that because "the method is immaterial to the claim," Amgen's claims were valid despite failing to describe all the methods that could be used to produce human EPO, including TKT's endogenous activation techniques. Id. at *50.

Furthermore, the Court held that the patent disclosure only needs to teach "one mode of making and using a claimed composition" to satisfy the enablement requirement. Id. Therefore, because Amgen's claims did not require "unpredictable technology" or a "high quantity of experimentation," the Court concluded that Amgen's patents could claim the entire genus of cells used to produce human EPO even though it only disclosed several specific mammalian and vertebrate cells that could be used to make the claimed invention. Id. at **54-55. However, although it agreed with the lower court's analysis in this particular case, the Court, particularly in light of Judge Clevenger's vigorous dissent, recognized that broad product and composition claims often leave themselves exposed to enablement challenges and restated the lower court's admission that the enablement questions in this case "were close." Id. at **49 fn. 9 & 64.

The Court also addressed TKT's challenge that the prior art Sugimoto patent anticipated Amgen's patents. The lower court held that, despite the apparent similarities contained in its unclaimed disclosures, the Sugimoto patent failed to invalidate Amgen's patents because TKT did not prove that these disclosures were enabled. While acknowledging that a prior art reference cannot anticipate a claimed invention unless it is enabled, the Court ruled that "a presumption arises that both the claimed and unclaimed disclosures in a prior art patent are enabled." Id. at *113. Because the lower court failed to recognize this presumption and instead placed the burden of proving enablement on TKT, the Court remanded and instructed the lower court to reconsider invalidity under section 102 in view of Sugimoto, with Amgen bearing the burden of proof on nonenablement.

In establishing this rebuttable presumption of enablement, the Court did not rely on prior case law or the presumption of validity for patents under section 282. Instead, the Court reasoned that, in the same way the patent examiner can reject an application claim "as anticipated by a prior art patent without conducting an inquiry into whether or not that patent is enabled," courts must presume the enablement of disclosures in prior art patents raised by an accused infringer. Id. at **113-14. By employing this reasoning, which it noted in dicta may also apply to prior art printed publications, the Court circumvented Amgen's argument that there was no presumption in this case because section 282 only presumes the enablement of a patent's claimed subject matter. Id. at **113 & 115 n.22. Thus, the Court found that when presented with a potentially invalidating prior art patent, the patentee must present persuasive evidence of nonenablement to overcome the presumption that both the claimed and unclaimed disclosures in that patent are enabled.

Implications

This case further highlights the challenges patent prosecutors face in balancing the benefits of drafting broad product and composition claims with the risks such claims face from invalidity challenges under section 112. While it is difficult to draw any bright-line rules from its section 112 analysis, the Federal Circuit's holding demonstrates that the written description requirements set forth in Eli Lilly and Enzo II will not be blindly employed in all section 112 challenges to biological patents. The more well known the biological material involved in the patent, the more likely the Court will distinguish the stricter requirements of Eli Lilly and Enzo II and uphold claims supported by broadly drafted written descriptions. Although the Court's section 112 analysis in Amgen may ultimately be limited to its facts, this case should reassure patent prosecutors that broad product and composition claims related to biological materials, which are not new or unknown, will more likely withstand challenges under section 112.

In contrast to its section 112 analysis, which may be limited to the facts of the case, the Amgen Court clearly established the manner in which courts must treat disclosures in prior art patents raised in validity challenges under section 102(a). The Court established a rebuttable presumption of enablement for all disclosures (both claimed and unclaimed) in prior art patents. The Court's ruling unquestionably places a larger burden on the patentee in an infringement case and encourages accused infringers to raise numerous challenges under 102(a) because the burden to overcome these challenges is now squarely on the patentee.

Further, the Court's reasoning arguably applies to prior art patents under section 102 generally; and the Court itself, in dicta, recognized its reasoning might also apply to prior art printed publications. Patentees should therefore be prepared to present evidence that prior art patent disclosures and printed publications are not enabled and, thereby, fail to serve as invalidating prior art under section 102.