Barr Labs challenges Argatroban patent

US generic drug group Barr Laboratories 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 containing a Paragraph IV certification for Argatroban. Encysive is the holder of the New Drug Application for the drug, 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 Food & Drug Administration in September 2007, and received notification of the application's acceptance for filing in November last year. Following receipt of the notice from the FDA, Barr notified the NDA holder and patent owner.

On December 28, 2007, Encysive announced that Mitsubishi Chemical Corp, the patent holder for Argatroban injections, Mitsubishi Tanabe Pharma, Encysive and GSK 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.