Validity affirmed for patents related to salt formation

A 3-judge panel of the Federal Circuit (Federal Circuit Judges Timothy Dyk, Kathleen O’Malley and Evan Wallach) affirmed an appeal of a Southern District of Florida decision from Watson Pharmaceuticals, Inc.  The per curiam order affirmed a 2011 decision that found valid Valeant’s four patents covering a particular salt formation of the antidepressant bupropion.  No. 10-20526, 2011 U.S. Dist. LEXIS 128742 (S.D. Fla. Nov. 7, 2011).  Watson argued that the patents were invalid as anticipated and/or obvious over the prior art.

Finding no single piece of prior art to be anticipatory, the central issue for the district court was whether the identification and use of a particular salt formation of bupropion was obvious.  According to the opinion, salt selection affected the stability of the dosage form and the salt ultimately chosen allowed for a more stable once a day dosage form and at higher strengths than the previously marketed bupropion salt.  In general, the patents-in-suit claimed methods for producing the desired formulations and methods of treating depression with those formulations.

In finding the patents not obvious or anticipated, the Florida district court relied on what the court called the “general rule” that salt selection is an unpredictable art.  The court noted that the defendants had failed to cite to any witness testimony or prior art that contradicted such “general rule.”  Watson’s expert testified that several prior art references suggested moving to the more stable salt as a way to solve stability problems.  But the court disagreed finding that some of the references actually taught away from the more stable salt and that others failed to suggest that an ordinary skilled artisan would reasonably expect improved stability.

The district court devoted two paragraphs of its opinion to distinguishing this case from that of Pfizer v. Apotex, 480 F.3d 1348 (Fed. Cir. 2007).  In Pfizer v. Apotex, the Court reversed a finding of non-obviousness, holding that changing the salt of amlodipine would have been obvious to one of skill in the art.  The Pfizer Court noted that as of the mid 1980’s, there may have been some degree of unpredictability in salt selection, but that “a rule of law equating unpredictability to patentability,” applied in its case, “would be that any new salt would be separately patentable, simply because the formation and properties of each salt must be verified through testing.”  Pfizer v. Apotex, 480 F.3d at 1364.  In distinguishing its decision from Pfizer, the Florida district court noted that the Pfizer Court had found numerous prior art references teaching that one could improve stability by switching to the particular salt selected.  In contrast, the bupropion prior art did not showcase a similar teaching.

Additionally, the Florida district court rejected the argument that given the technology available at the time, one of skill in the art would have included the more stable salt in a screen for alternative salts.  Watson argued that the availability of high-throughput screening as a means to rapidly create and test many salts at once could form the basis of a finding of invalidity based on obviousness.  The court rejected this argument, stating that after-the-fact testing cannot form the basis of a finding of obviousness.  Rather, the obviousness inquiry must focus on whether the ordinary skilled artisan could reasonably predict the favorable properties of the claimed invention in advance of any testing.