Du Pont, ImaRx sue MBI, Mallinckrodt

Du Pont Pharmaceuticals and ImaRx Pharmaceutical this month began another chapter in the patent infringement saga in which the companies have been embroiled since 1997. The two firms filed suit in a U.S. District Court in Delaware against Molecular Biosystems and Mallinckrodt, claiming infringement on patent no. 5,547,656. ImaRx owns the patent and licenses it to Du Pont.

The patent in question covers low-density, perfluorocarbon gas-filled microspheres used in ultrasound contrast agents, including Du Pont’s Definity product. Du Pont submitted a new drug application to the Food and Drug Administration for Definity last December and is awaiting clearance (SCAN 12/16/98).

The suit came less than a week after the U.S. Patent and Trademark Office upheld the patent, bolstering North Billerica, MA-based Du Pont and Tucson-based ImaRx’s confidence in their intellectual property position. On April 29, the PTO affirmed all 62 of the patent’s claims without amendment.

The PTO’s decision resolves one of two patent challenges brought against Du Pont and ImaRx in 1997 by MBI of San Diego and Mallinckrodt of St. Louis. Du Pont expects to receive a decision from the PTO in the near future regarding the other patent under reexamination, according to the company.