Pardon me skipping over other issues covered in the ruling, including the stereochemistry of atomic compositions; but trust me, stereo is better than mono; you can tell the difference.

Pfizer asserted only claim 6 of 5,273,995, one of the two asserted patents; the other: 4,681,893, to which Ranbaxy was found to have infringed through appeal. '995 claim 6 depends on claim 2, which depends on claim 1.

1. [R-(R *,R*)]-2-(4-fluorophenyl)-.beta.,.delta.-dihydroxy-5-(1-methylethyl)-3-phen yl-4-[(phenylamino)-carbonyl]-1H-pyrrole-1-heptanoic acid or (2R-trans)-5-(4-fluorophenyl)-2-(1-methylethyl)-N,4-diphenyl-1-[2-(tetrahy dro-4-hydroxy-6-oxo-2H-pyran-2-yl)ethyl]-1H-pyrrole-3-carboxamide; or pharmaceutically acceptable salts thereof.

2. A compound of claim 1 which is [R-(R*R*)]-2-(4-fluorophenyl)-.beta.-.delta.-dihydroxy-5-(1-methylethyl)-3 -phenyl-4-[(phenylamino)carbonyl]-1H-pyrrole-1-heptanoic acid.

6. The hemicalcium salt of the compound of claim 2.

The summary version is that the CAFC agreed with Ranbaxy's argument, ruling claim 6 invalid because it did not "narrow the scope of claim 2; instead, the two claims deal with non-overlapping subject matter." The CAFC explains -

With respect to the '995 patent, numerous issues have been raised on appeal. Rather than considering them in the order presented by the appellants, we first direct our attention to the question of validity under 35 U.S.C. § 112, ¶ 4, which provides:

Subject to the following paragraph [concerning multiple dependent claims], 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. A claim in dependent form shall be construed to incorporate by reference all the limitations of the claim to which it refers.

As described above, Pfizer only asserted dependent claim 6 of the '995 patent. This claim reads: "The hemicalcium salt of the compound of claim 2." Claim 2, in turn, is dependent on claim 1, which recites the following compounds: (1) atorvastatin acid; or (2) atorvastatin lactone; or (3) pharmaceutically acceptable salts thereof. Claim 2 itself, however, only recites atorvastatin acid. Notably, it does not include the pharmaceutically acceptable salts of atorvastatin acid.⁶ Ranbaxy asserts that the district court erred in refusing to invalidate claim 6, even though it does 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. In other words, claim 6 does not narrow the scope of claim 2; instead, the two claims deal with non-overlapping subject matter.

⁶ Theoretically, a claimed acid could be liberally construed to include the corresponding salts. See Merck & Co., Inc. v. Teva Pharms. USA, Inc., 347 F.3d 1367, 1372 (Fed. Cir. 2003). But here, given the absence of the "pharmaceutically acceptable salts thereof" language which was used in claim 1, the intrinsic evidence would not have supported such an interpretation of claim 2.

The district court, though troubled, was not able to find federal circuit precedent for § 112, ¶ 4, and so demurred from invalidating the claim. The district court was curious that the patent office failed to heed § 112, ¶ 4 by not rejecting the claim.

The district court explicitly recognized that "there may be a technical problem in the drafting of claim 6." Pfizer, 405 F. Supp. 2d at 508. Yet, it declined to find that "this drafting problem is sufficient to render the claim invalid if the claim is read consistently with its meaning to those skilled in the art" because it was unable to find any Federal Circuit precedent applying § 112, ¶ 4 to invalidate a patent. Id. at 508-09. The district court understood § 112, ¶ 4 "to be limited to matters of form, rather than matters of substance," noting that the PTO treats a claim that fails to comply with this provision "as a matter to be addressed through an objection" rather than rejected as unpatentable. Id. at 509. In any event, it emphasized that no objections were made to claim 6, (or any of the other similarly-worded dependent claims), during prosecution. Id. at 509 n.7.

It is true that at the time the district court wrote its opinion, there was no applicable Federal Circuit precedent. More recently, however, we have suggested that a violation of § 112, ¶ 4 renders a patent invalid just as violations of other paragraphs of § 112 would. Curtiss-Wright Flow Control Corp., 438 F.3d 1374, 1380 (Fed. Cir. 2006). In Curtiss-Wright, the issue was one of claim differentiation. The court reasoned that "reading an additional limitation from a dependent claim into an independent claim would not only make that additional limitation superfluous, it might render the dependent claim invalid" for failing to add a limitation to those recited in the independent claim, as required by 35 U.S.C. § 112, ¶ 4. Id. Indeed, "[i]nvalidity of the patent or any claim in suit for failure to comply with any requirement of sections 112 or 251 of this title" is expressly included among the available defenses to an infringement suit. 35 U.S.C. § 282(3) (emphasis added).

We recognize that the patentee was attempting to claim what might otherwise have been patentable subject matter.⁷ Indeed, claim 6 could have been properly drafted either as dependent from claim 1 or as an independent claim—i.e., "the hemicalcium salt of atorvastatin acid." But, we "should not rewrite claims to preserve validity." Nazomi Commc'ns, Inc. v. Arm Holdings, PLC, 403 F.3d 1364, 1368 (Fed. Cir. 2005); see also Rhine v. Casio, Inc., 183 F.3d 1342, 1345 (Fed. Cir. 1999) ("[I]f the only claim construction that is consistent with the claim's language and the written description renders the claim invalid, then . . . the claim is simply invalid."). Ranbaxy correctly argues that claim 6 fails to "specify a further limitation of the subject matter" of the claim to which it refers because it is completely outside the scope of claim 2. We must therefore reverse the district court with respect to this issue and hold claim 6 invalid for failure to comply with § 112, ¶ 4.

⁷ The district court found that claim 6 was unambiguous to the extent that the patentee intended to claim the hemicalcium salt of atorvastatin acid. Pfizer, 405 F. Supp. 2d at 507. The court further recognized that "[a]s a matter of standard chemical nomenclature, chemists typically refer to a salt of an acid, even though they are aware that the complete acid is technically no longer present in the salt form." Id. at 508.

Points for the legal team representing Ranbaxy in nailing the § 112, ¶ 4 argument on '995; too bad about that infringement decision for '893.