A federal appeals court decided not to rehear Purdue Pharma’s appeal of the Patent Trial and Appeals Board’s (PTAB) decision to invalidate its patents on abuse-deterrent formulations of extended-release OxyContin.

Purdue petitioned the court to rehear a challenge brought to PTAB by Amneal, in which the patent board ruled that Purdue’s patents were not prior art because they were obvious, taking Amneal’s side in the dispute.

The U.S. Court of Appeals for the Federal Circuit turned down Purdue’s appeal without giving a reason, upholding the PTAB ruling.