INNsight articles by Duncan Bucknell

The US Court of Appeals for the Federal Circuit has now confirmed that a patent claim can be invalidated on what was previously considered to be a minor technical defect.  (Basically, a dependant claim is invalid if it is not a subset of the claim from which it purports to depend.) 

While Ranbaxy won this point, its generic Lipitor was still held to have infringed Pfizer’s enantiomer patent which expires on 24 March 2010 (with pediatric exclusivity).

Pfizer Inc. v Ranbaxy Laboratories CAFC 06-1179 (2006)

The ‘995 patent was due to expire on 28 June 2011.  So, a typographical error in claim drafting may have cost Pfizer 15 months of market exclusivity in the USA.   This is probably in the order of US 1.25 billion (assuming that generic players obtain 50% of the market during that period).

Pfizer has foreshadowed that apart from appealing the Federal Circuit decision, it may seek to correct the defect before the USPTO.  Three mechanisms which Pfizer are presumably exploring are: (1) a certificate of correction (35 U.S.C. § 255), (2) Reissue (35 U.S.C. § 251) and (3) Re-examination (35 U.S.C. § 302 – though this requires prior art).

Comment

Until earlier this year, there was no Federal Circuit authority to support the notion that a claim could be invalidated on what seemed to be a narrow, technical point.  However, on 15 February, the CAFC handed down its decision in Curtiss-Wright Flow Control Group 438 F.3d 1374 (Fed. Cir. 2006) which confirmed that poor claim dependancy could lead to invalidity pursuant to 35 U.S.C. §112 ¶ 4, which states: 

“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.” 

The CAFC cited Curtiss-Wright in support of its finding of invalidity. 

Part of the rationale for allowing such a defect to invalidate the claim is that invalidation under §112 is an express defence to infringement in 35 USC 282(3).

The CAFC also appeared to caution lower courts against the temptation to rewrite claims in the form that was clearly meant.  (In the present case, the invalidated claim (claim 6), should have depended from claim 1.)

The claims in this case

In essence, claim 6 is dependant on claim 2 but does not narrow the scope of claim 2.  Instead, the two claims deal with non-overlapping subject matter.  The relevant claims are: 

Claim 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.

Claim 6 claims a hemicalcium salt and references claim 2.  However, Claim 2 does not include hemicalcium salts.  Claim 1 includes all pharmaceutically acceptable salts and so claim 6 should have been dependant on claim 1.

The District Court agreed that there was a defect in claim 6 but declined to invalidate it since there was no Federal Circuit precedent applying §112 ¶ 4 to invalidate a patent claim.

Background

The global scorecard

Here is an updated version of the status report from my previous article The global Lipitor patent battle: State of play and Pfizer’s recent win on appeal in the UK. 

 The CAFC Appeal

Ranbaxy appealed a 4 January 2006 judgment of the District Court of Delaware in Pfizer Inc. v Ranbaxy Labs. 405 F Supp 2d 495 (D. Del 2005) which held that:

(1) claim 1 of US 4681893 the ‘893 (enantiomer) patent was infringed,

(2) the ‘893 term extension was valid,

(3) claim 6 of US 5273995 (base) patent was infringed,

(4) that claim 6 of the ‘995 patent was not invalid under §112, or novelty or obvious or double patenting, and

(5) that the ‘995 patent was not unenforceable due to inequitable conduct.

The District Court’s claim construction was affirmed and consequently so was the finding of infringement.  As in other jurisdictions, the enantiomer patent was not restricted to the racemic mixture.