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Absence of Formal Relationship Between Applications Defeats Estoppel

April 23, 2002
Shaffer, Robert F.

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Last Month at the Federal Circuit - May 2002

Judges: Prost (author), Newman, and Gajarsa

In Abbott Laboratories v. Dey, L.P., No. 01-1374 (Fed. Cir. Apr. 23, 2002), the Federal Circuit vacated and remanded a district court’s grant of SJ of noninfringement, holding that (1) statements made during prosecution of an earlier-filed patent did not create an estoppel as to the scope of the later-filed patent; (2) hypothetical patent claims that would cover the accused composition would not have been anticipated or obvious based on the prior art; and (3) the patent’s recitation of specific numeric ranges for chemical components did not preclude any range of equivalents.

Abbott Laboratories (“Abbott”) sued Dey, L.P. and Dey, Inc. (collectively “Dey”) for infringement of U.S. Patent No. 4,397,839 (“the ‘839 patent”) and U.S. Patent No. 4,338,301 (“the ‘301 patent”). These patents both relate to a lung-surfactant composition for treating respiratory-distress syndrome in premature babies. The earlier-filed ‘301 patent represents the work of Drs. Fujiwara, Tanaka, and Takei in developing a surfactant having the desirable properties of rapid spreading in the lungs and of reducing ultra-alveolar surface tension. The relevant limitation in claim 1 of the ‘301 patent states: “the phospholipid content is 75.0-95.5%.”

In continuing his work based on the ‘301 patent, one of the three inventors, Dr. Tanaka, discovered that by increasing the content of free fatty acids from less than 1.0% as found in the ‘301 patented composition to a range of 1.0-27.7%, several important properties were enhanced. The ‘301 patent’s original composition contained less than 1.0% free fatty acid. Dr. Tanaka’s discovery of the benefit of the added free fatty acid led him to file the ‘839 patent application four months before the ‘301 patent issued. However, Dr. Tanaka filed the ‘839 patent application as a separate and independent application, even though the ’301 patent shared common subject matter and an inventor. The relevant limitation in claim 1 of the ‘839 patent reduces the percent of overall phospholipid content when compared with the ‘301 patent and adds an additional fatty acid content limitation: “the overall phospholipid content is 68.6-90.7%, the overall neutral fat content is 0.3-13.0%, the total cholesterol content is 0.0-8.0%, the overall free fatty acid content
is 1.0-27.7%.”

In a preliminary injunction motion, Abbott attempted to prove infringement of the ‘839 patent only under the DOE, conceding that Dey’s product did not literally meet claim 1’s limitation of 68.6- 90.7% phospholipid. Abbott’s own testing of the product found higher percentages—91.8% and 94.5% phospholipid. The district court had precluded Abbott from relying on the DOE, however, because (1) the ‘839 patent was an improvement patent—not a pioneer patent; (2) Abbott’s expert testimony suggesting that a phospholipid percentage as high as 99.9% would effectively and improperly read out of the claim the phospholipid limitation; and (3) the court had concluded that a “hypothetical claim” of 94.5% phospholipid would not have been allowed over the prior art ‘301 patent.

The district court then granted SJ of noninfringement to Dey, stating that the patentees cannot recapture through the DOE the higher phospholipid percentage surrendered from the ‘301 patent with the issuance of the ‘839 patent.

The Federal Circuit disagreed. The Court reasoned that because the percent of phospholipid limitation was not discussed in the prosecution of the ‘839 patent, the district court had incorrectly based the estoppel on the ‘301 patent. In doing so, the Court concluded that the relationship between the two patents was insufficient to render arguments made during prosecution of the earlier-filed application (the ‘301 patent) equally applicable to the laterfiled application (the ‘839 patent). Noting that the ‘839 patent application was not filed as a continuation, continuation-in-part, or divisional application of the ‘301 patent application, the Court concluded that these applications had no formal relationship and, thus, were presented to the patent office as patentably distinct inventions.

The Federal Circuit also rejected the district court’s hypothetical claim analysis, which incorrectly denied any range of equivalents by comparing only the phospholipid claim limitation of claim 1 of the ‘839 patent with the ‘301 patent (the only prior art considered by the district court) while ignoring all other limitations of the claim. Also, because the ‘301 patent failed to disclose the claim limitations of free fatty acids in the amount of 1.0-27.7%, the Court held that the ‘839 patent surfactant was patentably distinct from the surfactant described in the ‘301 patent.

The Federal Circuit also rejected the district court’s decision that recitation of a specific numeric range precludes one from asserting the DOE and ruled that asserting the DOE to a phospholipid upper limit of 94.5% (the accused product’s percentage) does not eliminate the upper limit from the claim.