North American Scientific Presents Advances in Early Evaluation of Cancer Therapy at American Association of Cancer Research Annual Meeting.

Business Editors & Health/Medical Writers

CHATSWORTH, Calif.--(BW HealthWire)--April 9, 2002

Apomate(TM) Demonstrates Tumor Response to Treatment

Within Hours of Initial Course of Therapy

North American Scientific, Inc. (Nasdaq:NASI) today announced that results from Phase I and II clinical trials of Apomate(TM), a proprietary imaging agent under development by its Theseus Imaging subsidiary, were selected by the American Association for Cancer Research (AACR) for presentation at a press conference focusing on "Improving Outcomes by Individualizing Treatment with Patient-Tailored Cancer Therapy." The press conference was sponsored by the AACR and held in conjunction with the Association's 93rd Annual Meeting in San Francisco at which data about recent work on Apomate(TM) is being presented.

Dr. Neil Steinmetz, Vice President and Medical Director of Theseus, will summarize early results from phase I and II clinical trials designed to assess the safety of Apomate(TM) and the feasibility of using Apomate(TM) imaging for early prediction of chemotherapy response in a paper entitled "Early prediction of tumor chemotherapy response and prognosis based on Tc-99m Annexin V (Apomate(TM)) imaging after one course of chemotherapy." The paper reports studies demonstrating that Apomate(TM) localization, suggesting increased cell death, could be seen in some tumors within hours after an initial course of chemotherapy. In patients with lung cancer and lymphoma this increased localization correlated with objective response to chemotherapy and, in an initial group of 15 subjects, to patient survival time.

As the AACR stated in its Press Release, "The best hope for improving cancer treatment outcomes in the future, many researchers believe, rests on the ability to tailor therapy to the specific molecular and biochemical characteristics of individual patient's tumors." Apomate(TM) is under study for use as a molecular imaging agent for rapid characterization of individual patient's response to prescribed anti-tumor therapy.

"Apomate(TM) imaging continues to show promising results in clinical studies of patients with lung cancer and lymphoma," commented Dr. Allan M. Green, President of NASI's Theseus Imaging Corporation subsidiary. "The ability to demonstrate both apoptosis and necrosis -- the two major types of cell death -- in tumors in response to initial treatment may allow prediction of response to a wide range of therapies in other types of cancer as well. This could lead to the timely selection of more effective treatment for cancer patients. Such information may also allow the avoidance of ineffective therapy, which is expensive and can cause significant side effects without bringing significant benefit."

The studies reported at AACR were based on the hypothesis that tumors not demonstrating increased apoptosis after one course of chemotherapy are unlikely to respond to continuation of the same regimen. In an initial group of 15 patients followed for up to one year at a Belgian research site, 7 of 7 Apomate(TM) positive patients demonstrated complete (4) or partial (3) response to their treatment, whereas 6 of 8 Apomate(TM) negative patients had progression of their cancer or died. Statistical (Kaplan-Meier) analysis demonstrated increased survival of Apomate(TM) positive patients in comparison with the Apomate-negative population (p less than .01).

Co-authors on the paper included Drs. Neil Steinmetz and Allan Green of Theseus, Drs. Tarik Belhocine and Pierre Rigo of the Domaine Universitaire du Sart Tilman (Liege, Belgium), Drs. Guido Heidendaal II, Leo Hofstra, Paul W. Thimister, and Chris Reutlingsperger of the University of Maastricht (Maastricht, The Netherlands), Drs. Alison Stopeck and James Woolfenden of the University of Arizona (Tucson) and Dr. Hussein Abdel-Dayen of St. Vincent's Hospital (New York).

About Apomate(TM)

North American Scientific is developing Apomate(TM), a kit for the preparation of Technetium Tc-99m annexin-V, for the noninvasive detection of cell death. Apomate(TM)'s annexin component has been shown in ongoing clinical trials to selectively bind to phospholipids that are normally inside the membranes of healthy cells, but which become exposed to the blood stream during apoptosis or necrosis, the two major pathways of cell death. Apomate(TM) is designed to exploit the binding properties of annexin-V, allowing the use of nuclear medicine imaging of the Technetium Tc-99m marker to locate concentrations of Apomate(TM) uptake that correspond with areas of cell death. Apomate(TM) is currently in clinical trials to assess the early response of patients to chemotherapy, to determine the extent of damaged heart muscle following a heart attack or following the treatment of a heart attack, and to non-invasively detect early signs of heart transplant rejection.

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 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.

About AACR

Founded in 1907, the American Association for Cancer Research (AACR) is a professional society of more than 18,000 laboratory and clinical scientists engaged in cancer research in the United States, Canada, and more than 60 other countries. AACR's mission is to accelerate the prevention and cure of cancer through research, education, communication, and advocacy. Its principal activities include the publication of five major peer-reviewed scientific journals (Cancer Research; Clinical Cancer Research; Cell Growth & Differentiation; Cancer Epidemiology, Biomarkers & Prevention; and Molecular Cancer Therapeutics). Also, AACR holds an annual meeting with about 14,000 participants featuring presentations of new and significant discoveries in the cancer field, as well as 8-10 specialty meetings involving all of the important areas of basic, translational, and clinical cancer research.

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 Form 10-K for the fiscal year ended October 31, 2001 and subsequent 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.