U.S. Patent Office overturns Du Pont, ImaRx patent claims

No delays seen, however, for DMP-115 contrast agent

The ongoing ultrasound contrast patent saga continues. In response to a request filed by Molecular Biosystems and its marketing partner Mallinckrodt, the U.S. Patent and Trademark Office has rejected claims of some of the ultrasound patents owned by ImaRx Pharmaceutical and licensed to marketing partner Du Pont Merck. The rejected patent claims cover, in part, low-density, perfluorocarbon gas-filled microspheres used for medical imaging, according to Du Pont Merck.

Du Pont Merck and ImaRx aren’t giving up, however. The firms are preparing a defense of the patents and will be meeting with Patent Office officials in the next month to present their case. Du Pont officials expect the defense process will be completed by February 1999.

The patents at issue concern DMP-115, an ultrasound contrast agent developed by Tucson-based ImaRx and licensed to Du Pont Merck. Commercialization of DMP-115 will not be affected by the patent process, said Susan Nemetz, vice president of contrast imaging at Du Pont Merck, of North Billerica, MA. According to a deal signed in 1995, Du Pont Merck has rights to manufacture, market, and sell DMP-115 in North America, Latin America, Canada, and Europe.

Du Pont Merck and ImaRx fully expect to win their request to have their patents declared valid again, Nemetz said, noting that nearly 80% of patents subjected to re-examination by the PTO emerge valid and enforceable. In the event that the ruling by the PTO stands and further appeals are unsuccessful, however, there will be no lasting effect, Nemetz said.

“All that (the ruling) would say is that this technology is not proprietary, and everyone would have an opportunity to play,” she said.

In addition to the two patents that were rejected by the PTO, ImaRx and Du Pont Merck hold many other patents related to ultrasound contrast technology, Nemetz said.

Phase III clinical trials studying the ability of DMP-115 to opacify left endocardial borders and perform functional and perfusion imaging are in their final stages, Nemetz said. Du Pont Merck expects to file a new drug application (NDA) with the Food and Drug Administration within a year.

MBI officials were unavailable for comment at press time. In addition to the ImaRx patents, MBI and Mallinckrodt also have patent re-examination action pending against Nycomed and Sonus on their relevant patents (SCAN 3/4/98).