Process limitations in a claimed composition having no effect on the structure of the claimed composition will not be given patentable weight. Here, for example, a claim limitation specifying that a particular impurity in the pharmaceutical composition being claimed was derived from a newly discovered source was found to be insufficient to establish nonobviousness because the source of the impurity did not impact its structure or its removal. “It has long been established that one cannot avoid anticipation by an earlier product disclosure by claiming … the product as produced by a particular process.” It may therefore be best to avoid process limitations in product claims and/or to have separate method claims directed to the process itself.
Background / Facts: The patent being asserted here in response to a generic drug ANDA submission is directed to a reformulated version of the pain reliever OxyContin®. The specification describes methods for detecting and removing the impurity 14-hydroxycodeinone (“14-hydroxy”), which was discovered to be present at elevated levels due to the transformation of a particular oxidation byproduct (in its isomer “8α” form), among other conventionally known sources of 14-hydroxy. In this regard, the claims recite a pharmaceutical compositing having less than 25 ppm 14-hydroxy, “wherein at least a portion of the 14-hydroxy[] is derived from 8α[] during conversion of oxycodone free base to oxycodone hydrochloride.”
Issue(s): Whether the claim limitation specifying that the remaining 14-hydroxy in the claimed composition is derived from 8α—not previously known in the art as being a source of 14-hydroxy—should be given patentable weight.
Holding(s): No. “We agree with the district court that ‘derived from 8α[]’ does not describe the structure of 14-hydroxy and thus is a process limitation. The patent specification describes methods for detecting and removing 14-hydroxy without regard to the source. … Because the source of the 14-hydroxy has no effect on its structure or its removal through hydrogenation, the limitation that it be ‘derived from 8α[]’ cannot be a structural limitation.” Accordingly, “because ‘derived from 8α[]’ is a process limitation, the district court did not err in disregarding the limitation in its obviousness analysis.”