The U.S. Court of Appeals for the Federal Circuit in Washington today upheld an earlier decision that three patents held by Purdue Pharma LP can’t be enforced because of misrepresentations to the U.S. Patent and Trademark Office about the painkiller’s effectiveness thus giving Endo Pharmaceutical Holdings Inc. the right to sell a generic version.

OxyContin, a time-release painkiller generally prescribed to cancer patients and chronic-pain sufferers, had about $2 billion in sales last year. The drug is considered a controlled substance because its potential for abuse is similar to morphine’s.

This was a patent infringement case in which the patents were held unenforceable by the trial court due to inequitable conduct during prosecution before the USPTO. Purdue Pharma filed an infringement suit against Endo alleging that Endo’s proposed generic versions of OxyContin®, would infringe three Purdue patents. The district court found that Endo would infringe Purdue’s patents, but determined the patents were unenforceable due to the inequitable conduct that occurred during prosecution. Purdue appealed the inequitable conduct judgment.

The three patents asserted by Purdue against Endo are directed to controlled release oxycodone medications for the treatment of moderate to severe pain. The patents are related: U.S. Patents No. 5,656,295 (the “’295 patent”) and No. 5,508,042 (the “’042 patent”) are, respectively, a continuation-in-part and a divisional of U.S. Patent No. 5,549,912 (the “’912 patent”). The ’912 patent itself is a continuation-in-part of U.S. Patent No. 5,266,331 (the “’331 patent”), which Purdue has not asserted against Endo.

The “Detailed Description” section of the written description in each asserted patent opens with the following statement, which played a prominent role in the trial court’s inequitable conduct determination:

It has now been surprisingly 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 thrust of this language is that the invented oxycodone formulation using a four-fold range of dosages (e.g., between 10 mg and 40 mg) achieves the same clinical results as the prior art opioid formulations using an eight-fold range of dosages (e.g., between 10 mg and 80 mg). The written description later explains that the “clinical significance” of the four-fold dosage range of the oxycodone formulations of the present invention, as compared to other opioid analgesics, such as morphine, requiring twice the dosage range, is a more efficient titration process, which is the process of adjusting a patient’s dosage to provide acceptable pain relief without unacceptable side effects.

However, the trial court concluded that Endo had shown by clear and convincing evidence that Purdue’s patents were “invalid” due to Purdue’s inequitable conduct during prosecution of the patents before the PTO based its inequitable conduct determination on underlying findings of materiality and intent.

First, the court found that in view of Purdue’s repeated statements to the PTO that it had discovered an oxycodone formulation for controlling pain over a four-fold range of dosages for 90% of patients, compared to an eight-fold range for other opioids, Purdue failed to disclose material information because it did not inform the PTO that the “discovery” was based on “insight” without “scientific proof.” Second, the trial court found the record as a whole reflected a “clear pattern of intentional misrepresentation.”

Purdue contended it is irrelevant that it lacked scientific proof of the four-fold dosage range for oxycodone because the inventors never stated during prosecution of the patents that the discovery had been clinically tested, and thus did not expressly misrepresent a material fact. But that was not the basis for the trial court’s materiality finding. The court found Purdue had relied on its discovery of a four-fold dosage range throughout prosecution and failed to disclose material information that was inconsistent with its arguments for patentability.

Purdue first told the PTO it had “surprisingly discovered” the four-fold dosage range for controlled release oxycodone, compared to the eight-fold range for other opioids. In response to an obviousness rejection, under headings containing the phrases “Surprisingly Improved Results” and “Results Obtained,” Purdue distinguished its oxycodone formulations from other opioids based on the “surprising result” of the four-fold dosage range and its “clinical significance”—a more efficient titration process. Purdue presented this argument even though neither the written description nor the pending claims of the ’331 patent application made reference to the four-fold dosage range.

The court held that:

In light of Purdue’s consistent representations of the four-fold dosage range for controlled release oxycodone as a “surprising discovery” and the context in which that statement was repeatedly made, we cannot say the trial court’s finding that Purdue failed to disclose material information was clearly erroneous. While Purdue never expressly stated that the discovery of the four-fold dosage range was based on the results of clinical studies, that conclusion was clearly to be inferred from the language used by Purdue in both the patents and prosecution history.

Therefore, the court concluded that weighing materiality and intent is a matter of judgment and thus, the trial court’s findings on materiality and intent were well-founded, and thus not clearly erroneous.

The case is Purdue Pharma LP v. Endo Pharmaceuticals Inc., 04-1189, 04-1347 and 04-1357, all U.S. Court of Appeals for the Federal Circuit. See opinion here: Download file

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