Last month, the Federal Circuit affirmed the District Court of Delaware’s decision in Persion Pharmaceuticals v. Alvogen invalidating as obvious two Persion patents claiming methods of treating pain in patients with hepatic impairment (compromised liver functionality) using hydrocodone. Important to the Federal Circuit’s decision was the concept of “inherency.”

Often times “inherency” relates to the issue of anticipation – even though an anticipatory reference does not expressly disclose the presence of a claim element, the element can be present in the reference (and, thus, the reference can anticipate a patent claim) if the element is inherently (necessarily) present. In Persion, however, anticipation was not an issue. The issue was whether “inherency” could be used to support Alvogen’s obviousness attack.

Relevant Persion patent claims were directed to administering hydrocodone to patients with hepatic impairment and obtaining a specific hydrocodone release profile. Devane, the primary asserted reference, disclosed the use of an extended-release, hydrocodone-only product (Zohydro ER) to treat pain in patients with normal livers. As noted above, Devane did not anticipate the claimed methods, so there was no question about whether this reference inherently disclosed the required hydrocodone release profile in patients with hepatic impairment. The issue was whether the asserted references, when combined, inherently disclosed the required hydrocodone release profile in patients with hepatic impairment. As the Federal Circuit noted (emphasis added), “‘inherency may supply a missing claim limitation in an obviousness analysis’ where the limitation at issue is ‘the natural result of the combination of prior art elements.’”

This is a key point -- whereas “inherency” in an anticipation analysis focuses on whether a single disclosure necessarily contains a claim element, “inherency” in an obviousness analysis asks whether a hypothetical combination of references would necessarily contain the required element. “Inherency” in an obviousness attack thus focuses on whether an element is necessarily present in something which did not exist prior to the hypothetical combination.

In Precision, after Alvogen set forth its prima facie case of obviousness that one of ordinary skill in the art would have been motivated to combine the asserted references in a manner to arrive at methods of treating pain in patients with hepatic impairment using hydrocodone with a reasonable expectation of success, the required hydrocodone release profile was deemed to inherently result from this hypothetical combination of references. Stated another way, rather than Alvogen needing to show that the required release profile resulted from the combination of asserted art in patients having hepatic impairment, the required profile was presumed to necessarily be present through “inherency.” The ability to satisfy a claim element through “inherency” in this case, and in obviousness attacks generally, can be a significant advantage.

Of course, Alvogen’s attack might have been helped by the fact that previously-existing product Zohydro ER was covered by these two patents. Regardless, it does not detract from the basic point here that “inherency” might be a useful tool to satisfy claim elements in an obviousness attack so it should be kept in mind.