On February 3, 2017, the PTAB denied a petition by Amneal Pharmaceuticals LLC (“Amneal”) to institute an inter partes review of Hospira Inc.’s patent directed to pharmaceutical compositions of the sedative dexmedetomidine. The patent’s only independent claim recites:

1. A ready to use liquid pharmaceutical composition for parenteral administration to a subject, comprising dexmedetomidine or a pharmaceutically acceptable salt thereof disposed within a sealed glass container, wherein the liquid pharmaceutical composition when stored in the glass container for at least five months exhibits no more than about 2% decrease in the concentration of dexmedetomidine.

In its petition, Amneal relied in large part on the 2010 drug label for FDA approved Precedex, which is a concentrated dexmedetomidine solution that must be diluted in 0.9% sodium chloride prior to administration. Amneal argued that a person of ordinary skill in the art would have diluted Precedex according to its label to provide the claimed “ready to use” composition.

The PTAB disagreed, finding dispositive the claim limitation “wherein the liquid pharmaceutical composition when stored in the glass container for at least five months exhibits no more than about 2% decrease in the concentration of dexmedetomidine.” The PTAB rejected Amneal’s argument that because the Precedex label disclosed that the concentrated solution was “stable” for two years that the claim limitation was necessarily present. The PTAB explained that Amneal failed to show that “stable” is equivalent to the claimed “no more than about 2% decrease,” and the label also described stability only of the concentrated solution, not a “ready to use” solution.

The decision illustrates that reliance on the doctrine of inherency to attack the validity of patent claims requires more than probabilities or possibilities. Rather, it is necessary to provide evidence, usually in the form of expert testimony with experimental testing, that any missing claimed characteristic is necessarily present in the prior art.