Just before the New Year, the Federal Circuit affirmed a decision from the District of Delaware finding patent claims related to using Zohydro ER in patients having hepatic impairment (liver disfunction) invalid as obvious. Persion Pharm. LLC v. Alvogen Malta Oper. Ltd. Some of the claims at issue included pharmacokinetic limitations requiring that the serum concentration of the drug not exceed a particular threshold.

The district court found these claims invalid as obvious over a combination of prior art references including one reference to the claimed formulation and a few references that would have motivated a POSA to administer that formulation to patients with hepatic impairment and provided a reasonable expectation of success in so doing. The district court further found that although the prior art references did not explicitly disclose the pharmacokinetic limitations of the claims, these limitations were “inherent in any obviousness combination that contains the Devane formulation” because they were “necessarily present” in that formulation.

Neither party disputed that these pharmacokinetic limitations would have occurred when the formulation was used in individuals with hepatic impairment. Instead, the patent owner argued that the inherency doctrine did not apply in this case because the result was not inherent to any one prior art reference. The Federal Circuit rejected this argument, confirming that inherency can be used to satisfy claim limitations even when multiple references are combined to prove a claim is obvious.

This case highlights the strength of the inherency doctrine, particularly when used against claims that recite pharmacokinetic limitations. Defendants facing claims that recite pharmacokinetic limitations should be sure to consider whether they can prove that these limitations would necessarily be present upon combining prior art references.