During the early and mid-1990s, Purdue Pharma filed three patent applications for oxycodone formulations. The applications highlighted an unexpected finding:

It has now been surprisingly discovered that the presently claimed controlled release oxycodone formulations acceptably control pain over a substantially narrower, approximately fourfold [range] (10 to 40 mg every 12 hour-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.

But in 2000, when Purdue sued Endo Pharmaceuticals, alleging that Endo's generic drug would infringe its three patents, Endo contended that the court should not enforce the patents because Purdue had not explained to the patent examiner that the discovery had been a product of an inventor's theory-based insight, unsupported by data. Federal district and appellate court judges inferred that Purdue had intended to deceive the patent examiner and declared Purdue's...

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