Assertions of obviousness based on prior art references in combination with “routine optimization” by one skilled in the art are common in the chemical and biological fields. The Federal Circuit recently addressed this issue in E.I. DuPont De Nemours & Co. v. Synvina C.V., reversing the Patent Trial and Appeal Board’s (PTAB’s) finding that Synvina’s patent was non-obvious, in view of close prior art references and little to no additional evidence of non-obviousness.

DuPont requested inter partes review of Synvina’s U.S. Patent No. 8,865,921 (“the ’921 Patent”), seeking to invalidate the patent as obvious over three prior art references. The ’921 Patent is directed to methods for preparing 2,5-furan dicarboxylic acid under a particular set of reaction conditions. Specifically, Claim 1 recites:

A method for the preparation of 2,5-furan dicarboxylic acid comprising the step of contacting a feed comprising a compound selected from the group consisting of 5-hydroxymethylfurfural (“HMF”), an ester of 5-hydroxymethylfurfural, 5-methylfurfural, 5-(chloromethyl)furfural,5-methylfuroic acid, 5-(chloromethyl)furoic acid, 2,5-dimethylfuran and a mixture of two or more of these compounds with an oxygen-containing gas, in the presence of an oxidation catalyst comprising both Co and Mn, and further a source of bromine, at a temperature between 140°C and 200°C at an oxygen partial pressure of 1 to 10 bar, wherein a solvent or solvent mixture comprising acetic acid or acetic acid and water mixtures is present.

The three prior art references cited in the IPR disclose various methods of oxidizing HMF, including with acetic acid as a solvent; in air; with a catalyst comprising Co and/or Mn, bromine, and optionally zinc; at temperatures between 50-160°C; and at an oxygen partial pressure of 2.1-10.5 bars. DuPont argued that because the ranges in the prior art overlapped with the claimed ranges, that the claims were presumptively obvious. Despite Synvina providing little additional evidence suggesting the claims were inventive over the references (“unexpected” yields that were very close to, or overlapping with, the yields in the prior art references, and a long-felt need that may not have been met by the claimed process), the PTAB found Claims 1-5 and 7-9 of the ’921 Patent to be nonobvious over these references.

At the Federal Circuit, DuPont argued that the overlapping ranges in the prior art provided a presumption that the claims were obvious, and that this presumption was not overcome by the weak evidence suggesting nonobviousness. The Court agreed, reiterating that “where there is a range disclosed in the prior art, and the claimed invention falls within that range, the burden of production falls upon the patentee to come forward with evidence” of teaching away, unexpected results, or other pertinent evidence of nonobviousness. See Opinion at 17. Here, since DuPont provided sufficient evidence to demonstrate prima facie obviousness, the burden then shifted to the patentee to provide, for example: (i) evidence of a new and/or unexpected result; (ii) a teaching away from the claimed ranges in the prior art; (iii) evidence supporting that the prior art merely taught ranges that were so broad they were not amenable to routine optimization; or (iv) evidence supporting that the claimed parameters were not result-effective variables.

This opportunity to rebut a prima facie case of obviousness is a reminder to consider this type of evidence during the application drafting process. When claiming a range of values for a variable, it is important to consider both the known teachings in the art, as well as any additional evidence that would support the nonobviousness of the claimed range. For example, if one skilled in the art would have expected a decrease in the yield of a reaction under the claimed conditions, but the yield actually increases significantly, such unexpected results may tip the case in the patentee’s favor. Similarly, if the claimed conditions were cautioned against in the prior art (a “teaching away”), this provides additional evidence to show that the claimed conditions are nonobvious in view the art. These factors should be considered during application drafting in order to provide the advantageous position for addressing close prior art references.

Written by: Caleb A. Bates, Ph.D. & Jing Liu, Ph.D.