Annexin Imaging Technology Highlighted in Presentations at the 15th Annual Congress of the European Association of Nuclear Medicine.

Business Editors & Health/Medical Writers

CHATSWORTH, Calif.--(BUSINESS WIRE)--Sept. 10, 2002

North American Scientific Inc. (Nasdaq:NASI) today announced that its scientists and physicians presented the results of a Phase I study for safety, biodistribution and dosimetry of its Hynic-Annexin V product candidate, a kit for the preparation of Tc-99m labeled Annexin V, currently under study for in vivo imaging of cell death (apoptosis and necrosis). The presentation was made at the 15th Annual Congress of the European Association of Nuclear Medicine (EANM) held in Vienna August 31 - September 4, 2002.

The results of the Phase I study demonstrated that the Hynic-Annexin V imaging agent was well tolerated in normal volunteers and that, after intravenous administration, the agent is cleared from the body by the kidneys. The study showed that Hynic-Annexin V is not cleared by the hepatobiliary system to any significant extent, and that, unlike previous formulations of Tc-99m labeled Annexin V, there was no bowel excretion of the agent. The absence of gastrointestinal clearance suggests that abdominal imaging should be relatively straightforward with Hynic-Annexin V.

In addition, two other annexin related presentations by independent researchers were nominated for the Marie Curie Award of the EANM. These presentations focused on various potential applications for Tc-99m labeled Annexin V, including evaluation of the cardiac toxicity associated with the anticancer drug, doxorubicin, and assessment of intervention in acute myocardial infarction.

A study by Bennink, van den Hoff, van Hernert, deBrun, Spijkerboer and van Eck-Smit from the Academic Medical Center, Amsterdam, titled "Annexin V Imaging of Acute Doxorubicin Cardiotoxicity (Apoptosis) in Rats" showed that Tc-99m labeled Annexin V could detect apoptotic (dying) cells associated with doxorubicin cardiac toxicity. Rats treated for 3, 4, or 5 weeks with doxorubicin (one dose per week) showed significantly higher uptake of Annexin V after the final treatment. Histology confirmed apoptosis in the treated groups, demonstrating an increasing percentage of cardiomyocites apoptosis with an increasing cumulative doxorubicin dose. This commonly used chemotherapeutic agent is known to be associated with cardiac dysfunction in patients, and the authors conclude that Tc-99m labeled Annexin V imaging may be useful in assessment of this dysfunction.

Thimister, Heidendaal and colleagues at the University of Maastricht in the Netherlands presented a study titled "Disappearance of Apoptosis in the Subacute Phase of Acute Myocardial Infarction," which showed that evidence of programmed cell death associated with acute heart attacks could disappear within 2 to 3 days after successful reperfusion of the infarcted region of heart muscle. Three patients studied 4 to 8 days after the onset of acute myocardial infarction did not show Annexin V uptake at the time of imaging. Six other patients studied from 5 to 41 hours after the onset of acute myocardial infarction showed measurable Annexin V uptake in the acute phase of the disease process. Persistence of evidence of cell death in the period 4 to 8 days post-infarction was associated with larger infarctions with greater abnormalities in cardiac specific enzyme release. This data is consistent with the hypothesis that early reperfusion of blocked cardiac blood vessels may limit muscle cell death post MI and that rapid clearance of apoptotic and necrotic cells can take place within a few days of the initial insult. Clinical studies for the use of annexin imaging to evaluate interventions intended to limit the damage caused by acute blockage of a coronary blood vessel have been proposed by several investigators.

The recognition of the importance of in vivo imaging of cell death in several potentially important research and clinical settings continues to support the belief that Hynic-Annexin V imaging may be an important new clinical technique in the diagnosis and therapeutic management of cancer and heart disease.

"Though not surprising, we are pleased to see positive study results of new potential applications for Hynic-Annexin V taking place in Europe in addition to North America," commented L. Michael Cutrer, President and CEO of North American Scientific. "We expect to continue to support preclinical and clinical trials of the Hynic-Annexin V technology in leading healthcare centers in the European Union and are grateful for the support shown by the medical community for this work."

About North American Scientific

North American Scientific designs, develops and produces innovative radioisotopic products, including brachytherapy seeds and radiopharmaceuticals, principally for the treatment and diagnosis of disease. Its lead radiopharmaceutical product candidate is Hynic-Annexin V which is based upon the Apomate(TM) technology platform and is a kit for the preparation of Technetium Tc-99m labeled Annexin V (a naturally occurring human protein produced by recombinant techniques). It is administered intravenously and is intended for the in vivo imaging of apoptosis and necrosis, two common forms of cell death. For more information, please visit the company's Web site at www.nasi.net.

Statements included in this release that are not historical facts may be considered forward-looking statements that are subject to a variety of risks and uncertainties. There are a number of important factors that could cause actual results to differ materially from those expressed in any forward-looking statements made by the Company including, but not limited to, uncertainties relating to drug discovery and clinical development processes, the impact of competitive products and technological changes, changes in relationships with strategic partners and dependence upon strategic partners for the performance of critical activities under collaborative agreements, uncertainties relating to patent protection and regulatory approval, the stable supply of appropriate isotopes, the impact of competitive products and pricing, research and development estimates, market opportunities, risks associated with strategic opportunities or acquisitions the company may pursue and the risk factors included in the company's filings with the Securities and Exchange Commission. Any forward-looking statements contained in this news release speak only as of the date of this release, and the Company undertakes no obligation to revise or update any forward-looking statements, whether as a result of new information, future results or otherwise.