At the Seventh International Symposium on Positive-Strand RNA Viruses in June 2004, AVI reported results of a study conducted with the CDC to evaluate the ability of AVI's NEUGENE drug candidates to inhibit replication of dengue virus serotypes 1 through 4. The study determined that all four dengue serotypes could be inhibited by a single NEUGENE compound designed specifically for that purpose. This NEUGENE drug candidate was found to inhibit viral titer by up to one millionfold.

AVI believes its NEUGENE antisense "rapid response therapeutics" have a significant role to play in the future of anti-viral therapeutics. NEUGENES are synthetic compounds that mirror a critical portion of a disease-causing organism's genetic code and bind to specific portions of the target genetic sequence. Like a key in a lock, NEUGENE antisense compounds are designed to match up precisely with a specific gene or viral sequence, blocking the function of the target gene or virus.

About Dengue Virus

According to the CDC, dengue fever and dengue hemorrhagic fever (DHF) are viral diseases transmitted by mosquitoes. Dengue is the most rapidly expanding disease in most tropical and subtropical areas of the world. An estimated 50 million to 100 million cases of dengue fever occur each year, 200,000 to 500,000 of which are DHF. The disease is caused by one of four dengue virus serotypes. Epidemics caused by all four virus strains have become progressively more frequent and larger in the past 20 years. After an incubation period of from three to 14 days, dengue fever is characterized by a sudden onset of high fever, severe frontal headache, and joint and muscle pain. Many patients also experience nausea, vomiting and a rash. The serotype of the infecting virus, as well as the age, immune status and genetic predisposition of the patient, can all affect whether a person develops general dengue fever or the far more severe and life-threatening DHF. More information about dengue can be found at the CDC Web site, http://www.cdc.gov/ncidod/dvbid/dengue/index.htm.

About AVI BioPharma

AVI BioPharma develops therapeutic products for the treatment of life-threatening diseases using two technology platforms: third-generation NEUGENE antisense drugs and cancer immunotherapy. AVI's lead NEUGENE antisense compound is designed to target cell proliferation disorders, including cardiovascular restenosis, cancer and polycystic kidney disease. In addition to targeting specific genes in the body, AVI's antiviral program uses NEUGENE antisense compounds to target single-stranded RNA viruses, including West Nile virus, SARS coronavirus, hepatitis C virus, and dengue virus. AVI's second technology, AVICINE®, is a therapeutic cancer vaccine with late-stage trials planned for the treatment of pancreatic cancer. More information about AVI is available on the company's Web site at http://www.avibio.com.

"Safe Harbor" Statement under the Private Securities Litigation Reform Act of 1995: The statements that are not historical facts contained in this release are forward-looking statements that involve risks and uncertainties, including, but not limited to, the results of research and development efforts, the results of preclinical and clinical testing, the effect of regulation by the FDA and other agencies, the impact of competitive products, product development, commercialization and technological difficulties, and other risks detailed in the company's Securities and Exchange Commission filings.