Impax Labs challenges patent on bladder-control drug

HAYWARD, Calif. — Drug maker Impax Labs is hoping to become the first to market a generic version of a drug used to treat incontinence and overactive bladder, the company said Wednesday.

Impax announced that it had filed a regulatory application with the Food and Drug Administration for fesoterodine fumarate extended-release tablets in the 4-mg and 8-mg strengths, a generic version of Pfizer's Toviaz. Impax said its application contained a Paragraph IV certification, a legal assertion that the patents covering the drug are invalid, unenforceable or not at risk of being infringed upon.

In response, Pfizer and UCB Pharma filed a patent-infringement suit against Impax in the U.S. District Court for the District of Delaware. The lawsuit places a stay of final FDA approval on the generic for 30 months or until the companies settle the case. According to FDA records, the agency approved the drug in October 2008, and the patents covering it are scheduled to expire in 2019, 2022 and 2027.

Toviaz in the 4-mg and 8-mg strengths had sales of about $159 million during the 12-month period that ended in May, according to IMS Health.