IP News

On Feb. 1, 2006, in response to a petition for rehearing, the U.S. Court of Appeals for the Federal Circuit vacated the opinion in Purdue Pharma L.P. v. Endo Pharms. Inc., 410, F.3d 690 (Fed Cir. 2005) (affirming trial court's decision that Purdue's patents were unenforceable due to inequitable conduct), and issued a new opinion. In the new opinion, the Federal Circuit remanded to the trial court for further proceedings.

The three patents asserted by Purdue against Endo (U.S. Patent Nos. 5,656,295, 5,508,042, and 5,549,912) are directed to controlled release oxycodone medications for the treatment of moderate to severe pain. The “Detailed Description” section of the written description in each asserted patent begins with the following statement:

It has now been surprisingly discovered that the presently claimed controlled release oxycodone formulations acceptably control pain over a substantially narrower, approximately four-fold (10 to 40 mg every 12 hours ' around-the-clock dosing) in approximately 90% of patients. This is in sharp contrast to the approximately eight-fold range required for approximately 90% of patients for opioid analgesics in general.

Endo filed an Abbreviated New Drug Application (“ANDA”) with the FDA in September 2000, seeking approval to make and sell a generic version of Purdue's OxyContin formulation. At the same time, Endo notified Purdue that it had filed a paragraph IV certification asserting that Purdue's patents either would not be infringed by Endo's generic drug or were invalid. Purdue filed a patent infringement suit against Endo in October 2000. After an 11-day bench trial, the trial court found by a preponderance of the evidence that Endo's proposed generic drug products would infringe Purdue's patents. However, the trial court also found that Endo had shown by clear and convincing evidence that Purdue's patents were unenforceable due to inequitable conduct during prosecution of the patents. The trial court's determination was based on its finding that Purdue had repeatedly told the PTO that it had discovered the fourfold range for oxycodone while failing to inform the PTO that this discovery was based on “insight” without “scientific proof.”