With three judges filing dissenting opinions, the U.S. Court of Appeals for the Federal Circuit denied Pfizer’s petition for rehearing and rehearing en banc of its April 2007 decision finding a new salt form of a composition obvious in view of the prior art and holding that a motivation to combine references can be gleaned from the nature of the problem to be solved. Pfizer Inc. v. Apotex, Inc., Case No. 06-1261 (May 21, 2007) (Michel C.J.; Newman J.; Lourie J.; Rader J., dissenting)
Pfizer owns U.S. Patent No. 4,879,303 (the ’303 patent), which relates to amlodipine besylate, marketed as Norvasc®. Pfizer was previously awarded U.S. Patent No. 4,572,909 (the ’909 patent), which discloses 10 pharmaceutically acceptable acid addition salts of amlodipine and describes maleate as the preferred salt. Pfizer scientists subsequently encountered two problems with the amlodipine maleate tablet formulation: chemical instability and stickiness. After testing seven other acid addition salts of amlodipine, Pfizer settled on amlodipine besylate and filed a further U.S. patent application that matured into the ’303 patent. During prosecution, the examiner initially rejected the claims as obvious over the ’909 patent in view of secondary references. Pfizer overcame the rejection by filing a declaration from one of its scientists stating that the besylate salt of amlodipine is a unique compound and not an obvious one.
As reported in the IP Update (Vol. 10, No. 4), the original panel decision stated that "obviousness cannot be avoided simply by a showing of some degree of unpredictability in the art so long as there was a reasonable probability of success" and pointed to Pfizer’s supplemental FDA filing, which indicated that the besylate salt of amlodipine would work for its intended purpose. The panel also rejected Pfizer’s assertion that amlodipine besylate would have been, at most, obvious to try, noting that only one parameter needed to be varied via routine testing and that the prior art taught a specific approach to the problem rather than only a "general approach that seemed to be a promising field of experimentation." The panel further rejected the district court’s finding of unexpected results because the record showed no evidence of what the skilled artisan would have expected. Summarizing its findings, the panel concluded that "[a]t most, then, Pfizer engaged in routine, verification testing to optimize selection of one of several known and clearly suggested pharmaceutically acceptable salts to ease its commercial manufacturing and marketing of the tablet form of the therapeutic amlodipine." Pfizer subsequently filed a petition for a rehearing en banc.
Although en banc rehearing was denied, three judges dissented. In her dissent, Judge Newman accused the panel of misapplying the obvious-to-try standard as well as declining to consider the unexpected result represented by the stability and lack of stickiness of the besylate salt. Judge Newman alleged that the panel changed "the criteria and analysis of patentability." Judge Lourie, in his dissent, charged the panel with erring in its legal determinations and predicted that the panel’s errors will confuse the law relating to the rebuttal of a prima facie case of obviousness for a chemical compound. Judge Rader, in the final dissent, noted that three separate district courts held trials involving the patent in suit and came to the same factual conclusion regarding the non-obviousness of amlodipine besylate. Echoing Judge Lourie’s dissent, Judge Rader concluded that, given that the district court’s factual determinations were not clearly erroneous, the panel should have deferred to those factual findings. With regard to the panel’s "obvious to try" analysis, Judge Rader noted that "[w]ith unpredictable pharmaceutical inventions, this court more wisely employs a reasonable expectation of success analysis," and since salt selection is unpredictable, there would be no reasonable expectation of success in this case.
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