Pain for Purdue Pharma: CAFC affirms inequitable conduct finding

Surprisingly DiscoveredPurdue Pharma L.P. v. Endo Pharms. Inc. (Fed. Cir. 2005).

by Marcus Thymian

The Federal Circuit affirmed a finding by the District Court for the Southern District of New York that Purdue’s Oxycontin patents-in-suit are unenforceable due to inequitable conduct that occurred during prosecution of the patents.  The decision, if it withstands further appeal efforts, would open the door to generic equivalents of Purdue’s popular controlled-release pain treatment medication.  According to various news stories on the Federal Circuit ruling, Purdue has indicated it plans to request en banc review of the 3-judge panel decision by the full 12-judge Federal Circuit. 

The inequitable conduct determination was based primarily on variations of the following Purdue statement:

    It has now been surprising discovered that the presently claimed controlled release oxycodone formulations acceptably control pain over a substantially narrower, approximately four-fold [range] (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.

The district court found that Purdue repeatedly referred to this “surprising discovery” during prosecution, but did not inform the PTO that the “discovery” was based on “insight” without “scientific proof.”  The Federal Circuit decided that the district court did not error in finding the two elements of inequitable conduct: materiality and intent.

Materiality was based on the district court’s examination of the entire record.   Purdue had repeatedly argued that the four-fold dosage range distinguished the invention over prior art, according to the district court.  The district court found that Purdue’s use of language that “implied, if not suggested” experimental results, when in reality the “discovery” was based solely on inventor “insight,” constituted withholding material information from the PTO.

Intent was inferred from the context in which Purdue’s statements were made.  Purdue’s “carefully chosen language suggests that it had obtained clinical results, and that suggestion was left unclarified by any disclosure that discovery of the four-fold dosage range for oxycodone was based on insight.”  The Federal Circuit agreed that Purdue had engaged in a “clear pattern of misdirection throughout prosecution of Purdue’s controlled release oxycodone patents.”

This case is an interesting exercise in standards of review and burdens of proof and persuasion.  Inequitable conduct requires a showing by “clear and convincing evidence,” which is quite high (patent infringement requires only a showing by a “preponderance of the evidence”).  The Federal Circuit conducted a deferential review of the district court’s inequitable conduct ruling.  This heightened standard involves reviewing the materiality and intent factual findings for “clear error” and reviewing the ultimate inequitable conduct conclusion for an “abuse of discretion.”  So, while an initial inequitable conduct showing is a tough burden, if a district court’s ruling is well supported, it may be relatively tough to overturn. 

Marcus Thymian is a partner at McDonnell Boehnen Hulbert & Berghoff LLP in Chicago.  Concentrating primarily on the electrical, software, and mechanical arts, he is experienced in planning, creating, enforcing, and defending against patent portfolios. [Marcus Thymian’s Bio]

[Copyright 2005 – Originally published at]