U.S. Patent Office to Reconsider Validity of Nycomed Contrast Agent Patent.

SAN DIEGO--(BW HealthWire)--Sept. 25, 1997--Molecular Biosystems, Inc. (NYSE: MB) ("MBI"), today announced that it has received notice from the U.S. Patent Office ("PTO") that the PTO has granted MBI's petition seeking reexamination of the patentability of U.S. patent No. 5,529,766 issued to Nycomed Imaging AS on June 25, 1996.

Although MBI had requested reexamination of select claims, the PTO's order subjects all 30 claims of the Nycomed patent to reconsideration of whether any of those claims are patentable.

Nycomed has asserted that it holds patents, including the 5,529,766 patent that cover products in the ultrasound contrast agent field, including MBI's agent OPTISON(TM). In reaction to this assertion, MBI recently filed a petition asking the PTO to reexamine U.S. patent No. 5,529,766.

The PTO's order reviews in detail certain of the prior art references brought to the PTO's attention in MBI's reexamination petition. The key prior art references include several that Nycomed did not disclose to the PTO in its original patent application. The order concludes that certain of these references raise substantial new questions concerning the patentability of the Nycomed patent claims.

MBI's reexamination petition contended that the use of certain perfluorocarbon gases for ultrasound imaging were not patentable because of numerous prior art references. The PTO's order granting MBI's petition specifically noted that the prior art teaches the use of Freon(R) gases in ultrasound imaging, and that perfluoropropane is a Freon(R) gas.

Additionally, the PTO's order further noted that the prior art includes publications which specifically teach certain gases as useful for ultrasound contrast imaging, including sulfur hexafluoride and "low molecular weight fluorinated hydrocarbons."

Concluding that "there is a substantial likelihood that a reasonable (patent) examiner would consider these teachings important in deciding whether or not the claims are patentable," the PTO's order sets in motion the administrative procedures necessary to address the substantial new issues of patentability raised by MBI's petition.

MBI, based in San Diego, is a world leader in the development and manufacture of ultrasound contrast agents for medical imaging. MBI shares are listed on the New York Stock Exchange under the symbol "MB." ALBUNEX(R), the first FDA-approved ultrasound imaging agent, is currently marketed in the United States by Mallinckrodt Medical, Inc. (NYSE: MKG).

This news release contains forward-looking statements that involve risks and uncertainties. The outcome of the PTO's reexaminations of Nycomed patent may differ materially from MBI's expectations.

Among the factors that could result in a materially different outcome are Nycomed's defenses to MBI's petition for reexaminations, the discovery of information relating to the validity of the Nycomed patent not known to MBI and adverse findings of fact or rulings by the PTO. An adverse outcome in the reexamination proceeding may adversely affect MBI as it may support the validity of the Nycomed patent. -0-

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CONTACTS: Molecular Biosystems, Inc.

Gerard A. Wills, 619/824-2219

Stephen F. Keane, 619/824-2212

Patricia Sullivan, 619/824-2262