Before Wallach, Clevenger, and Stoll. Appeal from the United States District Court for the District of Delaware.

Summary: Regulatory guidelines addressing drug product impurities may serve as a market force in motivating a PHOSITA to modify prior art references. However, if the guidelines lack a solution overcoming the impurity issues, they cannot provide a PHOSITA with a reasonable expectation of success to achieve the claimed purity levels.

Endo asserted patent claims against Actavis covering a purified form of oxymorphone, a compound used for pain relief. Actavis argued that the claims were invalid as obvious in view of several prior art references, including FDA guidelines requiring that oxymorphone compounds contain less than 0.001% of a particular impurity, a limitation that Endo incorporated into its claims and relied on for patentability. The district court rejected Actavis’ obviousness arguments, reasoning that there was insufficient evidence to show that a PHOSITA would have had a reasonable expectation of success in combining the cited prior art to achieve the claimed invention..

The Federal Circuit affirmed, acknowledging that the FDA guidelines provided an economic incentive to achieve the patented invention, but also that they did not provide any instruction on how to achieve that result. Thus, the FDA guidelines failed to adequately motivate a PHOSITA to combine the other cited prior art references, and do so with a reasonable expectation of success. Judge Stoll dissented, emphasizing that the FDA guidelines comprised every limitation included in the claims, and criticized the majority for improperly conflating the enablement and “reasonable expectation of success” inquiries.

This case is: ENDO PHARM, INC., v. ACTAVIS LLC

Editor: Paul Stewart

Written by: Benjamin Anger & Adam R. Aquino