The Federal Circuit has for the first time invalidated a patent under 35 U.S.C. §112, ¶4, which requires dependent claims to incorporate all limitations of the independent base claim and to place further limitation on that claim. The subject patent happens to cover Lipitor®, the world's largest selling drug. What seems clear is that practitioners should no longer distinguish between procedural and substantive patentability requirements under Title 35 in considering which ones may form a basis for invalidity.

In Pfizer v. Ranbaxy, No. 06-1179 (Fed. Cir. Aug. 2, 2006), the Federal Circuit affirmed the finding that Pfizer's `893 patent was infringed by Ranbaxy's proposed atorvastatin product, but reversed the determination that the `995 patent was not invalid under §112, para. 4.

Pfizer's `893 and `995 patents relate to atorvastatin calcium (Lipitor®), the world's largest-selling drug. Claim 1 of the `893 patent recites a compound having a generic structural formula with two chiral centers, and the parties agreed that the R-trans enantiomer was specifically depicted. Although four isomers are contemplated, the specification limited the invention to only the trans-form enantiomers. Ranbaxy argued that the claim was limited to racemates based on the reaction sequences in the specification that produce only racemates, as well as statements made in the prosecution of both foreign counterparts and in the unrelated `995 patent. But neither the district court nor the Federal Circuit was persuaded. According to the Federal Circuit, a claim construction that relied on the product of the examples would improperly import limitations into the claims. In addition, statements made in foreign counterpart applications were "irrelevant" because they were made in response to requirements unique to the laws of other jurisdictions. Nor were statements made during the prosecution of the later-issued `995 patent considered relevant to interpretation of the `893 patent claims. Ranbaxy was thus held to infringe Claim 1 of the `893 patent.

Pfizer only asserted dependent claim 6 of the '995 patent, which recites "[t]he hemicalcium salt of the compound of claim 2." Claim 2, in turn, depends from claim 1, which recites atorvastatin acid or atorvastatin lactone or pharmaceutically acceptable salts thereof. Claim 2 itself, however, only recites atorvastatin acid. Notably, it does not include the pharmaceutically acceptable salts of atorvastatin acid.

Ranbaxy asserted that the district court erred in refusing to invalidate claim 6, even though it did not "incorporate by reference all the limitations of the claim to which it refers" and "then specify a further limitation of the subject matter," as required by §112, ¶ 4. The Federal Circuit agreed, first noting the absence of precedent on the issue, but then holding as a matter of first impression that failure to comply with §112, ¶ 4 was a basis of invalidity. According to the Court, its conclusion was "consistent with the overall statutory scheme that requires applicants to satisfy certain requirements before obtaining a patent, some of which are more procedural or technical than others." The court declined to reach the remaining invalidity arguments raised by Ranbaxy.

A copy of the case is available for your reference.

To discuss these topics further, please feel free to contact the author, Michael R. Dzwonczyk (mdzwonczyk@sughrue.com), at Sughrue Mion, PLLC in Washington DC, USA.

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