By Kevin E. Noonan --
In the non-precedential General Atomics case decided earlier this month, the Federal Circuit applied its Markman claim construction practice to a Jepson claim, a venerable claim format seen more frequently in the mechanical and electrical arts than in the chemical or biotechnology arts (1). The case illustrates the tendency for the CAFC to parse claim language very finely and almost hyper-technically, and the prevailing attitude on the Federal Circuit that patentees should and must pay the price for claim language that does not adequately protect their technology from being practiced in a non-infringing manner.
The case involved a diagnostic assay for homocysteine, an amino acid derivative normally found in trace amounts in blood and urine. Elevated levels have been associated with a variety of ailments, including cardiocascular disease. Axis-Shield, the patentee, asserted two patents, U.S. Patent Nos. 5,631,127 and 5,958,717, in its countersuit to General Atomics' declaratory judgment action. Claim 1 of the '127 patent reads:
1. In a method for assaying homocysteine in a sample, said method comprising the steps of:
(i) contacting said sample with a homocysteine converting enzyme and at least one substrate for said enzyme other than homocysteine, and
(ii) assessing an analyte which is a substrate for said enzyme,
wherein the improvement comprises in step (i) contacting said sample with a said substrate other than homocysteine and in step (ii) without chromatographic separation assessing a non-labelled analyte selected from the group consisting of a homocysteine co-substrate and the homocysteine conversion products of the enzymic conversion of homocysteine by said enzyme.
Claim 1 of the '717 reads:
1. In a method for assaying homocysteine in a sample, said method comprising the steps of:
(i) contacting said sample with a homocysteine-converting enzyme and
(ii) assessing an analyte,
wherein the improvement comprises in step (ii) without chromatographic separation assessing a non-labelled analyte selected from the group consisting of the homocysteine conversion products of the enzymic conversion of homocysteine by said enzyme.
(underlining was added in the case as reported, to identify the limitations that were the focus of the Federal Circuit's determinations).
Consistent with Jepson claiming, the novel aspects of these claims are the limitations following the word "improvement" in each claim; the recitations prior to "improvement" are in the prior art.
The accused assays detected homocysteine using an assay having the following steps:
1) a co-substrate referred to as S-adenosyl-L-methionine ("SAM") is added to the sample;
2) an enzyme referred to as homocysteine-methionine methyl transferase ("HMTase") is then added;
3) the HMTase acts to remove a methyl group from the co-substrate SAM and attach it to the homocysteine, converting the homocysteine into methionine and SAM into S-adenosyl-L-homocysteine ("SAH");
4) simultaneously, a second enzyme is added, SAH-hydrolase, which catalyzes a reaction that converts SAH to adenosine and non-sample homocysteine;
5) additional steps occur, involving adenosine deaminase and spectrophotometric monitoring, to determine the level of SAH produced.
The assay took advantage of the following reaction pathway:
The basis for General Atomics' assay was that the amount of SAH was proportional to the levels of homocysteine in a sample; the assay assessed the amount of SAH by spectrophotometry.
Axis-Shield asserted two theories of infringement: that sample homocysteine was coverted by HMTase (the "homocysteine converting enzyme") by combination with SAM (the "homocysteine co-substrate"). The assay produced two "homocysteine conversions products," SAH and methionine, and the assay detected SAH without chromatographic separation. In its alternative theory, Axis-Shield asserted that SAH hydrolase was the homocysteine converting enzyme, adenosine was the homocysteine co-substrate, and SAH was the homocysteine conversion product.
The case turned, as is frequently the case, on the meaning of the claim terms (underlined above). In order to infringe, according to the District Court, the analyte detected ("assessed") in the General Atomics assay must either be a homocysteine co-substrate or a homocysteine conversion product. And the District Court found the analyte assessed in the accused assay (SAH) was neither, based on either of Axis-Shield's infringement theories.
The Federal Circuit, in a unanimous decision written by Judge Lourie (Judges Gajarsa and Dyk concurring) construed the claims de novo in the face of Axis-Shield's contention that the District Court had misconstrued the claims, specifically the terms "homocysteine conversion product," "homocysteine converting enzyme," and "homocysteine co-substrate." Judge Lourie reviewed the District Court's definition of the term "homocysteine conversion product" as a product that must be derived from homocysteine, and agreed with this construction based on the plain meaning of the claim language. Specifically, the claim itself recites that the homocysteine conversion products are products of "enzymic conversion of homocysteine by said enzyme." Judge Lourie made a distinction between the language of the claim and hypothetical language more in keeping with the construction Axis-Shield argued on appeal, "homocysteine conversion reaction products." In Judge Lourie's view, this language would permit the claim to be construed to encompass detection of "any product" produced by the homocysteine conversion reaction. In contrast, according to Judge Lourie, the actual claim language specifically recited a homocysteine conversion product, which would include methionine but not SAH. SAH, in the CAFC's opinion, is a conversion product of SAM, not homocysteine. The opinion finds support in the specification as well, citing the "first embodiment" of the invention disclosed therein as being the production of SAH by SAH hydrolase. In this reaction, according to the Federal Circuit, adenosine is the homocysteine co-substrate, SAH hydrolase is the homocysteine converting enzyme, and SAH is the homocysteine conversion product.
The CAFC also rejected Axis-Shield's contention that the specification disclosed embodiments wherein homocysteine acted as an inhibitor of SAH hydrolase, so that detection of the adenosine content of the reaction is a measure of the amount of homocysteine in the sample. The Federal Circuit noted that claims do not always (and are not required to) encompass all disclosed embodiments, particularly in view of prosecution strategies. In this case, Axis-Shield had originally asserted another patent, No. 6,063,581, having claims to the inhibitor embodiments, and the Federal Circuit characterized as "inapt" Axis-Shield's claim construction arguments to have these embodiments fall within the scope of either the '717 or '127 claims.
The CAFC also affirmed the District Court's construction that General Atomics' assay did not infringe under Axis-Shield's alternative infringement theory, because it "cannot differentiate between SAH produced from SAH hydrolase reaction and from the HMTase reaction.
Besides the rarity of having the Federal Circuit construe a Jepson claim in a biotechnology patent, this case is another example of the CAFC's propensity to place the burden of an unfavorable claim construction on the patentee (at least with regard to constructions that do not support a finding of infringement); see Sage Products Inc. v. Devon Indust. Inc. This has some logic as policy, since the patentee is in the best position to claim her invention as broadly as her disclosure and the prior art permit. In addition, it provides incentives (if not rewards) for third parties to design around the patentee's claims, especially when the construction is based on the "plain meaning" of the claim language. But it also requires something akin to a crystal ball for patent prosecutors and inventors to craft claim language that adequately protects technology, and it is not yet clear whether the Federal Circuit is balancing these competing interests to provide the optimum amounts of both incentive and certainty.
(1) For example, the term "nucleic acid" yields 20,706 granted patents as a claim term, while the term "improvement" occurs in only 265 (1.3%) of them. In contrast, the term "attached" occurs 380,895 times, while the term "improvement" occurs in 21,409 (5.6%) of them.
General Atomics Diazyme Lab. Division v. Axis-Shield ASA (Fed. Cir. 2008)
Panel: Circuit Judges Lourie, Gajarsa, and Dyk
Opinion by Circuit Judge Lourie
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