On Friday, the Federal Circuit declined to give new life to two method-of-treatment patents, finding that their pharmacokinetic limitations were an inherent result of prior art elements, even while citing a combination of prior art references.

In Persion Pharmaceuticals LLC v. Alvogen Malta Operations Ltd., the appeals court faced a question of obviousness for a pain treatment for impaired-liver patients by administering hydrocodone bitartrate as the only active ingredient. Impaired liver function can affect the way that the body metabolizes hydrocodone. In the patents at issue, some claims stated that “the starting dose is not adjusted relative to a patient without hepatic impairment,” while other claims were explicitly limited to exclude increases in hydrocodone blood concentrations beyond a certain percentage, versus patients without kidney or liver impairments.

The district court found the claims obvious over a combination of prior art references:

• “Devane” taught the same formulation of hydrocodone bitartrate as in the patents at issue, but without mentioning anything about liver impairment. Still, the district court found that this reference inherently also taught the pharmacokinetic limitations

• “Jain” taught treatment with Vicodin CR (hydrocodone bitartrate as combined with acetaminophen) in which the pharmacokinetic parameters “were similar in normal subjects and subjects with mild hepatic impairment.”

• Vicodin and Lortab labels additionally taught hydrocodone-acetaminophen formulations which did not have precautions or dosage restrictions for patients with impaired liver function.

On appeal, the Federal Circuit discussed its precedents on the idea of inherency. Newly discovering a property or function of a known compound does not make the compound patentable. Accordingly, an inherent property or an inherent function can be something that is not recognized in the prior art. The court also cited an earlier decision discussing an inherent pharmacokinetic property which “add[ed] nothing of patentable consequence,” even in an obviousness context. However, the discussion of precedent also acknowledged that inherency cannot rely just on probabilities, but instead, has to pertain to something that is necessarily present, or the natural result of a combination of elements explicitly disclosed in the prior art.

Ultimately, the Federal Circuit upheld the district court’s obviousness ruling, characterizing the pharmacokinetic limitations as just a natural result of the combination of Devane, Jain, and the Vicodin and Lortab labels. The decision on appeal also stated that the pharmacokinetics did not add patentable weight to the claims.

As a precedential decision, the court’s opinion in this case may increase the difficulty in obtaining and maintaining patent coverage for pharmaceutical methods involving known formulations.