Annexin Imaging Technology Highlighted in 22 Presentations at the Society of Nuclear Medicine Annual Meeting.

Business Editors & Health/Medical Writers

CHATSWORTH, Calif.--(BW HealthWire)--June 17, 2002

North American Scientific Inc. (Nasdaq: NASI) announced today that scientists and physicians at its Theseus Imaging division were co-authors on six of the 22 peer-reviewed presentations focusing on annexin imaging at the 49th Annual Meeting of the Society of Nuclear Medicine held in Los Angeles June 15-19, 2002. Recombinant human annexin is the core targeting component of Theseus Imaging Corporation's Apomate(TM) imaging agent now under development for the noninvasive assessment of early response to anti-cancer treatment and for evaluation of myocardial damage in acute myocardial infarction and cardiac transplant rejection.

Results of Phase II studies of imaging of myocardial damage with Tc-99m rh-annexin in patients with acute myocardial infarction were presented in two papers. "Simultaneous Dual Isotope Tl-201/Tc99m-Annexin SPECT in Detection of Acute Myocardial Infarction: Initial Results of a Phase II Multicenter Trial," by Steinmetz, Taillefer, Hendel, Weiland, Berman, Travin, Fish, Mallett and Green reported the localization of Tc-99m annexin in regions of apoptosis and necrosis following acute myocardial infarction. Follow-up of a subset of these patients was reported in a subsequent paper by Taillefer, Phaneuf, Duong, Benjamin, Lajeunesse, Ganon, Green and Steinmetz entitled: "Tc-99m Annexin V Scintigraphy in Detection of Acute Myocardial Infarction (MI): Repeat Imaging after the Onset of Acute Symptoms in order to Evaluate the Persistence of Abnormal Radiotracer Uptake." These authors found that Tc-99m annexin myocardial images performed within 96 hours of onset of acute symptoms may be used to detect acute MI, and that increased myocardial uptake of tracer tended to persist for about three weeks and then decrease over the subsequent 2-4 months.

A study by Taki, Higuchi, Tait, Strauss, Nakajima and Tonami entitled "Assessment of Apoptotic Process in an Acute Ischemia-Reperfusion Rat Model Using Tc-99 Annexin V" confirmed that Tc-99m annexin could detect apoptotic (dying) cells within 30 minutes after acute myocardial ischemia and reperfusion.

A French group including Peker, Sarda-Mantel, Loiseau, Nazneen, Meulemans, Martel, Vrigneaud and Le Guludec demonstrated the ability of Tc-99m annexin to image myocardial inflammation, known as myocarditis, in a rat model as reported in a paper entitled "Imaging Myocardial Apoptosis with Tc-99m Annexin in Experimental Myocarditis."

A number of papers also addressed the potential utility of Tc-99m annexin in the evaluation and identification of atherosclerotic plaque. In a paper entitled "Tc-99m Annexin V Versus F-18-FDG in the Identification of Atherosclerotic Plaques in APOE -/- Mice" Mari, Blankenberg, Z. Narula, J. Narula, Ghazarossian, Tait and Strauss reported the localization of both Tc-99m annexin and F-18 fluorodeoxyglucose in different atheroma lesions, depending on the stage of plaque progression. These authors found that the highest peak uptake ratio, peak-to-blood ratio and other imaging measures occurred with annexin V, suggesting that "apoptosis may play a significant role in atheroma identification." This result was supported by a paper by Gnanasekeram, Kolodgie, Petrov, Vermani, Weber, N. Narula, Strauss, and J. Narula entitled "Noninvasive Targeting of Apoptotic Macrophages in Atherosclerosis with Radiolabelled Annexin V for Potential Detection of Plaques Vulnerable to Rupture." The latter authors reported that annexin V was found in macrophage-rich areas of the atherosclerotic plaque and appeared to target apoptotic (dying) macrophages. Current theory suggests that dying macrophages cause instability of plaque in coronary arteries which may lead to plaque rupture and sudden death. Identification of these "unstable" plaques during cardiac catheterization might allow their effective treatment.

The recognition of the importance of in vivo imaging of cell death in several potentially important research applications continues to support the belief that Tc-99m annexin-V imaging may be an important new clinical technique in the diagnosis and therapeutic management of cancer and heart disease.

"We are pleased to see further study of new potential applications of Tc-99m annexin-V imaging, whose promise has been supported on a preliminary basis by a series of successful studies in multiple model systems suggesting that it may become a new agent in the provision of improved medical care," commented L. Michael Cutrer, President and CEO of 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 Apomate(TM), 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.