Barr Pharmaceuticals, Inc. confirmed that its subsidiary, Barr Laboratories, Inc., has initiated a challenge of the patent listed by Encysive Pharmaceuticals in connection with its Argatroban Injection (argatroban) 100mg/mL, 2.5mL vial.

The company believes that it is the first to file an Abbreviated New Drug Application (ANDA) containing a paragraph IV certification for Argatroban. Encysive Pharmaceuticals, Inc. is the holder of the New Drug Application (NDA) for Argatroban, which is manufactured for the US market by GlaxoSmithKline for Encysive.

Barr filed its ANDA containing a paragraph IV certification for a generic Argatroban product with the US Food & Drug Administration (FDA) in September 2007, and received notification of the application's acceptance for filing in November 2007. Following receipt of the notice from the FDA, Barr notified the New Drug Application (NDA) holder and patent owner.

On December 28, 2007, Encysive Pharmaceuticals Inc. announced that Mitsubishi Chemical Corporation, the patent holder for Argatroban injections, Mitsubishi Tanabe Pharma Corporation, Encysive and GlaxoSmithKline had filed suit in the US District Court for the Southern District of New York to prevent Barr from proceeding with the commercialization of its product. This action formally initiates the patent challenge process under the Hatch-Waxman Act.

Argatroban Injection (argatroban) 100mg/mL, 2.5mL vial is indicated as an anticoagulant for prophylaxis or treatment of thrombosis in patients with heparin-induced thrombocytopenia, and as an anticoagulant in patients with or at risk for heparin-induced thrombocytopenia undergoing percutaneous coronary intervention (PCI). The product had sales of approximately $111 million in the US, based on IMS sales data for the twelve months ended October 2007.

Barr Pharmaceuticals, Inc. is a global specialty pharmaceutical company that operates in more than 30 countries worldwide and is engaged in the development, manufacture and marketing of generic and proprietary pharmaceuticals, biopharmaceuticals and active pharmaceutical ingredients.