By Donald Zuhn —

In an
appeal from a District Court judgment holding claims 1-5 of U.S. Patent No.
5,527,814 (the '814 patent) enforceable, valid, and infringed, the Federal
Circuit affirmed the District Court's finding of no inequitable conduct,
vacated the District Court's finding that claims 1-5 of the '814 patent were
not invalid as anticipated, and remanded the case for further proceedings on
the issue of anticipation.

Defendant-Appellee Aventis Pharmaceuticals
Inc. (Aventis) owns the '814 patent, which relates to methods for treating
amyotrophic lateral sclerosis (ALS) using 2-amino-6-(trifluoromethoxy) benzothiazole, commonly referred to as
riluzole.  Dr. Erik Louvel, the lone
inventor on the '814 patent, had discovered in comparative testing of eight
compounds on rat spinal cord cells, that only riluzole produced positive
results for all three of the key parameters tested.

Seeking
approval to market generic riluzole tablets for the treatment of ALS,
Plaintiff-Appellant Impax Laboratories, Inc. (Impax) filed an Abbreviated New
Drug Application (ANDA) with the FDA.  Impax became aware of the '814 patent in the course of preparing its
ANDA, and thereafter filed a declaratory judgment action in the District of
Delaware.  In its suit, Impax sought a
declaration that it had not infringed the '814 patent by filing its ANDA, and
that its proposed manufacture and sale of riluzole would not infringe the '814
patent.  In addition, Impax asserted that
the '814 patent was invalid over the prior art, as well as unenforceable due to
inequitable conduct.

Following a
bench trial, the District Court determined that Impax's manufacture and sale of
riluzole would infringe the '814 patent, and that Impax had not established
that the '814 patent was unenforceable due to inequitable conduct or that
claims 1-5 were invalid as anticipated by the prior art.  Impax appealed the District Court's
determination that it failed to prove that the '814 patent was unenforceable
due to inequitable conduct or invalid as anticipated.

On the
issue of enforceability, the Federal Circuit found that the District Court had
not erred in determining that some of Dr. Louvel's comparative testing results
were not material.  Before the District
Court, and again on appeal, Impax argued that Dr. Louvel had failed to disclose
the testing results for all of the eight compounds he tested, and therefore,
had withheld material information from the Patent Office.  In particular, Impax contended that Dr.
Louvel had failed to disclose the results for a compound that yielded positive
results for two of the three key parameters tested.  Aventis countered that the withheld data was
not material because only riluzole had yielded positive results for all three
parameters tested.  The Federal Circuit
concluded that "the district court correctly recognized that the
comparative test data did not produce results that indicated that any of [the
compounds for which data was withheld] was effective in treating ALS," and
therefore, found "no error in the ruling of the district court that the
[withheld test results] were not material under either Rule 56
standard."  The Federal Circuit also
concluded that the District Court had not erred in finding no intent to
deceive, and affirmed the District Court's ruling that the '814 patent was not
unenforceable due to inequitable conduct.

On the
issue of validity, Impax asserted before the District Court that Aventis' U.S.
Patent No. 5,236,940 (the '940 patent) and Aventis' French Application No.
2,640,624 (the '624 application), from which the '940 patent claims priority,
anticipate claims 1-5 of the '814 patent.  In particular, Impax contended that the '940 patent and '624 application
disclose a class of compounds that includes riluzole, and suggest that this
class of compounds may be used to treat ALS.  Aventis countered that the prior art cited by Impax was not enabling
because it did not provide specific instruction for using riluzole and, in
fact, taught away from using riluzole.

Citing
Rasmusson v. SmithKline Beecham Corp., 413 F.3d 1318 (Fed. Cir. 2005), as
standing for the proposition that "proof of efficacy is not required for a
prior art reference to be enabling," the Federal Circuit determined that
the District Court had focused on whether the prior art disclosed that riluzole
was effective for treating ALS rather than on whether the prior art enabled the
use of riluzole for treating ALS.  In
Rasmusson, the Federal Circuit had reversed a decision by the Board of Patent
Appeals and Interferences that a prior art reference disclosing a method of
treating prostrate cancer using finasteride was not enabling, and therefore,
not anticipatory, because the reference failed to demonstrate that finasteride
was effective in treating prostrate cancer.  The Federal Circuit determined that the instant case was similar to
Rasmusson, since "the district court stopped its analysis after concluding
that the [prior art] did not disclose the compounds of formula I [of the '814
patent] were effective in treating ALS," and failed to "determine
whether the [prior art] enables a person of ordinary skill in the art to treat
ALS with riluzole."

Finding
that the District Court had stopped short of completing a proper enablement
analysis, the Federal Circuit looked to the allegedly anticipatory references
to determine whether either was enabling.  With respect to the '624 application, the Federal Circuit noted that
"[w]hen a reference discloses a class of compounds, i.e., a genus, a
person of ordinary skill in the art should be able to 'at once envisage each
member of th[e] . . . class' for the individual compounds, i.e., species, to be
enabled" (citing In re Petering, 301 F.2d 676, 681 (C.C.P.A. 1962).  The Federal Circuit concluded that because
riluzole is just one of hundreds of compounds encompassed by the class of
compounds disclosed in that application, and because the '624 application does
not identify riluzole by name, the '624 application did not enable the use of
the species riluzole for treating ALS.  Thus, the Federal Circuit affirmed the District Court's finding that the
'264 application does not anticipate the '814 patent.

The Federal
Circuit, however, reached a different conclusion with respect to the '940
patent.  Noting that the '940 patent,
unlike the '264 application, identifies riluzole by name (by explicitly
exempting riluzole from formula I), the Federal Circuit concluded that this
reference could not be similarly dismissed as nonenabling.  Instead, the Federal Circuit vacated the
District Court's finding with respect to the '940 patent, and remanded the case to allow
the District Court to reach its own
legal conclusion as to whether this reference is enabled.

Finally, in a separate opinion in which he joined the majority on all issues except the anticipation determination, Judge Rader concluded that "[w]hile the trial court referred to effectiveness, its findings go beyond that narrow ruling and suffice to uphold its judgment," and further, that "the majority opinion provides even more evidence that the '940 patent is not an enabling reference for purposes of anticipating the '814 patent."

Thanks to MBHB attorney Brad Crawford for providing the structure of riluzole.

Additional Disclaimer:  MBHB represented Aventis in the above appeal.  To the extent that this case summary contains any opinions, the opinions would be of Dr. Zuhn and not Aventis or MBHB.