United States - Inequitable Conduct: Purdue Pharma v. Endo

Purdue asserted against Endo patents directed to controlled release of oxycodone medications for the treatment of pain. The specification of each patent asserted that it had been “surprisingly discovered” that the claimed formulations controlled pain with a range of dosages that was substantially narrower than the range required with known opiod formulations, such as morphine. During prosecution, the Examiner rejected the application on obviousness grounds but later allowed the claims based on Purdue’s explanations based on the narrower range of dosages.

However, a panel of the Federal Circuit Court of Appeals considered that representing to the Patent Office that such a narrower range had been “discovered,” while withholding that the discovery was based on insight without scientific proof, may have amounted to failure to disclose material information. In particular, Purdue a number of times during prosecution referred to the narrower range of dosages as a “result,” thus implying that clinical results had been obtained.

Moreover, the panel considered that such carefully chosen language also may have amounted to an intentional withholding of material information as to the source of Purdue’s “surprising discovery,” thus misleading the Examiner in determining patentability. On this basis, the panel initially held the patent unenforceable due to inequitable conduct because Purdue did not inform the Patent Office that the “discovery” was based on “insight” without “scientific proof” and because the prosecution history as a whole reflected a clear pattern of intentional misrepresentation.

In a rehearing of the case, the panel vacated its decision and remanded the case to the trial court to resolve factual issues concerning the level of materiality of the (mis)representation and scienter. The panel admonished the trial court to bear in mind that, when the level of materiality is relatively low, the showing of intention must be proportionally higher.