Impax Laboratories, Inc. has announced that the US Court of Appeals for the Federal Circuit upheld a lower court ruling in favour of Impax in its defense of a lawsuit brought by Alza Corporation, a Johnson & Johnson unit.

The suit alleged patent infringement related to Impax's filing of an Abbreviated New Drug Application (ANDA) for a generic version of Ditropan XL (Oxybutynin Chloride) tablets, 5, 10 and 15 mg. Alza Pharmaceuticals markets Ditropan XL for the treatment of urge urinary incontinence. US sales of Ditropan XL were approximately $350 million in the 12 months ended May 31, 2006, according to Wolters Kluwer Health.

"We are pleased that yet another court has seen through Alza's attempt to delay the availability to patients of a lower priced alternative to the branded drug," commented Larry Hsu, PhD., president of Impax. "We received tentative approval for Oxybutynin Chloride 5, 10 and 15 mg Extended Release tablets in February 2005. Final approval is now dependent on the US Food and Drug Administration's (FDA) resolution of a Citizen's Petition brought by Johnson & Johnson, and on the expiration of any marketing exclusivity. We believe that we were first to file an ANDA on the 15 mg dosage form, and thus could have 180 days of marketing exclusivity following final FDA approval."

The company's version of generic Ditropan XL is one of 12 products covered under its strategic alliance entered into in June 2001 with a subsidiary of Teva Pharmaceutical Industries Ltd. Following final FDA approval and the company's decision to launch, Teva is expected to market the product.