The 6,200,604 and 6,974,590 patents do not expire until 2019.

FENTORA was approved by the US Food and Drug Administration (FDA) in September 2006 for the management of breakthrough pain in patients with cancer who are already receiving and who are tolerant to opioid therapy for their underlying persistent cancer pain.

The lawsuit is based upon an Abbreviated New Drug Application (ANDA) filed by Watson seeking FDA approval for a generic equivalent of fentanyl buccal tablets to be sold in the United States.

Watson alleges that the above two FENTORA patents are invalid, unenforceable and/or will not be infringed by Watson's manufacture, use or sale of the product described in its ANDA.

"We believe that the proposed Watson ANDA product infringes our patents," Executive Vice President and General Counsel Jerry Pappert said.

"The FENTORA patents were approved by the United States Patent and Trademark Office based on the results of extensive research by CIMA LABS. We continue to believe that our patent position for this product is strong and intend to vigorously defend our Intellectual Property," he added.

The filing of this lawsuit is provided for by the Hatch-Waxman Act, a federal statute governing certain aspects of generic drug approvals.

Under that statute, the filing of the lawsuit stays any FDA approval of the Watson ANDA until the earlier of a district court judgment in favor of Watson or 30 months from the company's April 2008 receipt of a Paragraph IV certification letter from Watson.

Cephalon Inc. is an international biopharmaceutical company dedicated to the discovery, development and commercialization of innovative products in four core therapeutic areas: central nervous system, pain, oncology and addiction.