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Patent Held Invalid for Improper Claim Dependency Under 35 U.S.C. § 112

August 02, 2006

Decision icon Decision

Last Month at the Federal Circuit - September 2006

Judges: Michel (author), Schall, Dyk

[Appealed from: D. Del., Judge Farnan]

In Pfizer, Inc. v. Ranbaxy Laboratories Ltd., No. 06-1179 (Fed. Cir. Aug. 2, 2006), the Federal Circuit affirmed a district court’s finding of infringement of U.S. Patent No. 4,681,893 (“the ’893 patent”) and ruling that the ’893 patent term extension was not invalid. The Federal Circuit reversed on the question of invalidity of U.S. Patent No. 5,273,995 (“the ’995 patent”) pursuant to 35 U.S.C. § 112, ¶ 4. In doing so, the Court reiterated that the fourth paragraph of § 112 is an invalidating provision.

Stereochemistry is the study of the three-dimensional structure of molecules. Stereoisomers have the same molecular formula or atomic composition, but different spatial arrangements. Enantiomers are a pair of stereoisomers that are nonsuperimposable mirror images of each other and often have distinct physical properties. A racemate (or racemic mixture) is an equal mixture of two enantiomers.

The two patents-in-suit concern the active ingredient in the prescription drug Lipitor®, which is used to reduce low-density lipoprotein (LDL) cholesterol levels. The active ingredient in Lipitor® is atorvastatin calcium. Claim 1 of the ’893 patent recites a compound of structural formula I, drawn as having a particular configuration. The ’995 patent covers the compound atorvastatin calcium. The ’893 patent was to expire on May 20, 2006, but the PTO granted an extension pursuant to 35 U.S.C. § 156, extending the expiration date to September 24, 2009. The ’995 patent expires on December 28, 2010. After a bench trial, the U.S. District Court for the District of Delaware found both patents infringed, not invalid, and not unenforceable.

On appeal, the parties agreed that, under the district court’s claim construction, Ranbaxy Laboratories Ltd.’s (“Ranbaxy”) ANDA product infringes claim 1 of the ’893 patent. Ranbaxy argued that the district court erred in construing structural formula I recited in claim 1 to embrace all trans-form isomers instead of limiting it to racemates. The Federal Circuit disagreed, noting that the ’893 patent consistently describes the invention as a class of “trans” compounds. Moreover, the Court concluded that there was no disavowal of claim scope in the specification that would limit the ’893 patent to racemates. The Court especially noted that the terms “racemate” or “racemic mixture” do not appear in the ’893 patent; nor is claim 1, unlike claim 5, limited by “trans-(±),” which designates a racemate. Moreover, the Court agreed with the district court’s conclusion that the statements made during prosecution of foreign counterparts to the ’893 patent were irrelevant to claim construction because they were made in response to patentability requirements unique to Danish and European law. Likewise, the Court held that statements made during prosecution of the later, unrelated ’995 patent could not be used to interpret claims of the ’893 patent. Having concluded that claim 1 was correctly construed, the Court affirmed the finding of infringement.

The Court also affirmed the district court’s conclusion that the patent term extension was valid. Ranbaxy argued that because the ’893 patent does not cover the active ingredient in Lipitor®, it was not eligible for a patent term extension. Based on its construction of claim 1, however, the Court found that the ’893 patent did cover the active ingredient in Lipitor® and, thus, was eligible for a patent term extension under 35 U.S.C. § 156. Further, the Court concluded that the district court’s factual findings that there was no inequitable conduct were not clearly erroneous.

With regard to the ’995 patent, Pfizer, Inc. (“Pfizer”) asserted only dependent claim 6 against Ranbaxy’s ANDA product. The claim reads: “The hemicalcium salt of the compound of claim 2.” Claim 2 depends on claim 1, which recites atorvastatin acid, atorvastatin lactone, or pharmaceutically acceptable salts thereof. Claim 2, however, recites only atorvastatin acid; it does not include the pharmaceutically acceptable salts of atorvastatin acid.

The Court noted that, pursuant to 35 U.S.C. § 112, ¶ 4, “a claim in dependent form shall contain a reference to a claim previously set forth and then specify a further limitation of the subject matter claimed.” Ranbaxy argued that claim 6 fails to “specify a further limitationof the subject matter” of claim 2 because it is completely outside the scope of claim 2. The district court recognized the drafting problem in claim 6, but did not render the patent invalid under § 112, ¶ 4, because the court was unaware of any Federal Circuit precedent invalidating a patent under this paragraph.

The Federal Circuit reversed, noting that “[i]nvalidity of the patent or any claim in suit for failure to comply with any requirement of sections 112 or 251” is expressly included in the list of defenses to a claim of patent infringement provided for by 35 U.S.C. § 282(3). Further, the Court concluded that finding the fourth paragraph of § 112 to be invalidating is consistent with the overall statutory scheme requiring applicants to satisfy certain requirements before obtaining a patent.

Accordingly, the Court remanded the case to the district court for modification of the permanent injunction.