US Court of Appeal invalidates Lipitor patent due to improper claim dependency

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)

‘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).

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. Â§ 255), (2) Reissue (35 U.S.C. Â§
251) and (3) Re-examination (35 U.S.C. Â§
302 — though this requires prior art).


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.
Â§112 Â¶ 4, which states:

â€œa claim in dependent form shall contain a reference to a
claim previously set forth and then specify a further limitation of the
by reference all the limitations of the claim to which it refers.â€

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

Part of the rationale for
allowing such a defect to invalidate the claim is that invalidation under
Â§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
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

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.

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


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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 Â§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.

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