Dependent Claim Failed to Specify a Further Limitation

A technical claim drafting problem in Pfizer, Inc., et al. v. Ranbaxy Laboratories, Limited, et (Fed. Cir. ; August 8, 2006) led to the invalidity of Claim 6 of U.S. Patent No. 5,273,995 under 35 U.S.C. § 112, ¶ 4, which requires

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.

Dedpendent claim 6, with intervening claims 1 and 2, recited

1. [R-(R *,R*)]-2-(4-fluorophenyl)-.beta.,.delta.-dihydroxy-5-(1-methylethyl)-3-phenyl-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.

In a footnote, the court acknowledged that, 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.

However, according to Chief Judge Michel,

We recognize that the patentee was attempting to claim what might otherwise
have been patentable subject matter. 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.

Although the district court was reluctant to find the fourth paragraph of §
112 to be an invalidating provision, doing so does not exalt form over
substance. Rather, it is 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. See, e.g., 35 U.S.C.
§ 102(b) & (d) (establishing statutory one-year bars to patentability); 35
U.S.C. § 111(a)(2)(C) (requiring submission of an oath by the applicant); 35
U.S.C. § 111(a)(3) (requiring submission of a fee with the application); 35
U.S.C. § 116 (requiring joint inventors to apply for a patent jointly).