AVI BioPharma Updates Results from Department of Defense Funded Collaborative Programs; NEUGENE Antisense Agents Effective at Combating Ebola and Marburg Viruses and Ricin and Anthrax Toxins.

PORTLAND, Ore. -- Tenth graph, second sentence, should read: The anthrax lethal toxin (LT) activates host proteins (sted: The anthrax lethal toxin (LT) activates cellular phosphatases)

The corrected release reads:

AVI BIOPHARMA UPDATES RESULTS FROM DEPARTMENT OF DEFENSE FUNDED COLLABORATIVE PROGRAMS; NEUGENE ANTISENSE AGENTS EFFECTIVE AT COMBATING EBOLA AND MARBURG VIRUSES AND RICIN AND ANTHRAX TOXINS

AVI BioPharma, Inc. (Nasdaq:AVII) today announced results from four programs partially funded by The United States Department of Defense (DoD) and in collaboration with the U.S. Army Medical Research Institute of Infectious Diseases (USAMRIID) at Fort Detrick, Md. AVI has successfully used its NEUGENE(R) antisense technology to combat the Ebola and Marburg viruses and to interrupt the cellular mechanism that ricin and anthrax toxins employ to induce lethal toxicity.

Ebola and Marburg Virus Results

Ebola virus studies in three animal species have been conducted at USAMRIID. The studies provided evidence of robust efficacy in multiple experiments conducted on mice, guinea pigs and nonhuman primates. Previous attempts by USAMRIID to treat Ebola virus with other technologies have demonstrated few successes in treating all three species.

Using Ebola virus mouse and guinea pig models, AVI targeted six of the seven Ebola virus genes with multiple compounds. The compounds were used as single agents and in combinations in prophylactic and therapeutic models. Among these studies, the most effective protocols, where 100 percent survival was observed at low doses of drug, were three-drug combinations targeting different Ebola genes when administered 24-48 hours after virus challenge.

Several of the antisense compounds that were efficacious in the mouse studies were also studied in the guinea pig model as single agents and in combinations. The guinea pig model was employed because it is a more rigorous model for Ebola virus efficacy. Results were similar to what was observed in the mouse studies with therapeutic protocols using combination agents being most effective.

Based on the mouse and guinea pig experience, a three-drug combination was used in initial nonhuman primate studies and also was successful. Consistent with previous preclinical and clinical studies in other disease settings, AVI's NEUGENE compounds were well-tolerated, from a safety perspective, by the NEUGENE-treated nonhuman primates.

In experiments designed to evaluate NEUGENE antisense agents targeting the Marburg virus, the guinea pig animal model was used, and the experimental design was similar to the studies on Ebola virus. More than 20 antisense compounds directed against multiple Marburg genes as single agents have been tested first in vitro, as well as in both prophylactic and therapeutic regimens in a guinea pig model of Marburg virus.

In animals challenged with high doses of the virus that were nearly 100 percent lethal in untreated animals, a high survival rate was observed in single agent protocols targeting distinct Marburg genes. The antisense agents were virus-specific; antisense treatment targeting Ebola virus did not protect animals against Marburg virus. Combination therapeutic studies, such as those that provided the most potent efficacy against Ebola virus, are currently underway for Marburg virus in guinea pigs.

Ricin Toxin Results

Ricin is an enzymatic toxin from the caster bean. It is composed of two peptides, one responsible for cell entry and the other for toxicity. Once inside the cell, the ricin enzyme cuts ribosomal RNA at the crucial initiation site. Without a functional initiation site, the cell cannot produce proteins, and cell death is rapid.

AVI's approach was to use NEUGENE antisense agents designed to block the ricin target site on ribosomal RNA, and therefore interfere with ricin enzymatic activity. Experiments conducted in cell-free systems indicated that ricin activity was inhibited with antisense blocking of the initiation site. In cell culture studies, where ricin was 100 percent lethal, greater than 75 percent cellular viability was achieved with antisense targeting the ricin binding site on ribosomal RNA. These preliminary results indicated that the approach was feasible and proof of principle has been established.

Anthrax Results

Anthrax is caused by toxins produced after infection with Bacillus anthracis. The anthrax lethal toxin (LT) activates host proteins that go on to trigger the apoptotic or cell-death pathway in cells that are infected. The approach that AVI and USAMRIID have taken to counter this cycle was to target host proteins that the anthrax toxin uses. In this manner, if the infected cells are inhibited from expressing the anthrax target, then apoptosis will not be induced and cell death will be reduced or prevented.

Experiments conducted in cell culture indicated that antisense targeting the relevant genes significantly down-regulated its expression, which led to increased cell survival without extensive apoptosis. Preliminary survival experiments in mice showed that almost all antisense-treated mice survived a lethal challenge with anthrax spores. Together, these experiments indicate proof of principal of the approach, and more robust experimentation is planned.

AVI's Partnership with USAMRIID

USAMRIID is the only laboratory in the DoD and one of only a few laboratories in the United States equipped to safely study highly hazardous infectious agents such as Ebola virus. Ebola virus often causes hemorrhagic fever, which historically has killed up to 80 percent of infected humans. As such, Ebola virus requires the maximum biocontainment and security, biosafety level 4 (BSL-4).

"Protecting the military and citizens from a possible bioterror threat remains an urgent and highly critical mission," said Sina Bavari, Ph.D. chief of immunology, target identification, and translational research, USAMRIID. "The results announced today not only represent important progress for the potential treatment of these deadly biothreats, but also evidence of the DoD's ability to rapidly and successfully partner with private industry to enhance our nation's biodefense efforts."

"We believe AVI's technology, which has demonstrated an excellent pharmacokinetic and safety profile in humans, may be directed against a broad range of potential biodefense threats, and we are encouraged by the results we have seen to date," said Denis R. Burger, Ph.D., chief executive officer of AVI. "Our work with the DoD allows us to develop drugs that have an important public health impact, and we are now applying our technology to address the potential emergence of avian influenza H5N1."

About Ebola Zaire and Marburg Viruses

Ebola hemorrhagic fever is a severe, often-fatal disease in humans and nonhuman primates (monkeys, gorillas and chimpanzees) that has appeared sporadically since its initial recognition in 1976. The disease is caused by infection with Ebola virus, named after a river in the Democratic Republic of the Congo (formerly Zaire) in Africa, where it was first recognized. Ebola virus and Marburg virus are the only two members of a family of RNA viruses called the Filoviridae.

Researchers have hypothesized that the first patient becomes infected through contact with an infected animal. After the first case-patient in an outbreak setting is infected, the virus can be transmitted in several ways. People can be exposed to Ebola virus from direct contact with the blood and/or secretions of an infected person.

The disease is a National Institute of Allergy and Infectious Disease (NIAID) priority A pathogen and a bioterrorism suspect agent of interest to the Department of Defense and Project BioShield. There are currently no approved treatments for Ebola.

Marburg virus was first recognized in 1967, when outbreaks of hemorrhagic fever occurred simultaneously in laboratories in Marburg and Frankfurt, Germany, and in what is now Serbia. Marburg hemorrhagic fever is a rare, severe type of hemorrhagic fever that affects both humans and nonhuman primates. Caused by a genetically unique animal-borne RNA virus, its recognition led to the creation of this virus family.

The most recent outbreak of Marburg virus started in October 2004 in Angola. According to the World Health Organization (WHO), as of Aug. 23, 2005, the Ministry of Health (MOH) of Angola had reported a total of 374 cases of Marburg hemorrhagic fever with 329 fatalities. The toll far exceeds the previous worst outbreak recorded in Angola's neighbor country, the Democratic Republic of Congo, in 1998, when 123 people died.

About Ricin Toxin

Ricin, a plant toxin from the seeds of the castor bean, is one of the most poisonous naturally occurring substances known and is poisonous to people, animals and insects.

Ricin inhibits protein synthesis by specifically and irreversibly inactivating ribosomes. These ribosome-inactivating proteins are typically monomers. However, to bind to the cell surface and enter the cell to reach the ribosomes, ricin requires a second monomer. Ricin, therefore, is a heterodimeric protein where the ribosome-inactivating enzyme, known as the A chain, is linked to the cell surface binding peptide, called the B chain. The ricin A chain of the heterodimer is the enzyme that binds and inactivates ribosomal RNA. Just a single ricin molecule that enters the cell can inactivate over 1,500 ribosomes per minute and kill the cell.

About Anthrax

Anthrax is an acute infectious disease caused by the spore-forming bacterium Bacillus anthracis. Bacillus anthracis is an encapsulated gram-positive, nonmotile, aerobic, spore-forming bacterial rod. Anthrax is most common in agricultural regions where it occurs in animals. When anthrax affects humans, it is usually due to an occupational exposure to infected animals or their products.

Three virulence factors account for majority of the clinical manifestations of Bacillus anthracis and are edema toxin, lethal toxin and an antiphagocytic capsular antigen. The lethal toxin is the most important in pathogenesis and primarily responsible for the primary clinical manifestations of hemorrhage, edema and necrosis.

In terms of bioterrorism, inhalation anthrax is the greatest concern. Case-fatality rates for inhalation anthrax are high, even with appropriate antibiotics and supportive care. Among the 18 cases of inhalation anthrax in the United States during the 20th century, the overall case fatality was greater than 75 percent. Following the bioterrorist attack in fall 2001, the case-fatality rate among patients with inhalation disease (all of whom received antibiotic therapy) was 45 percent (5/11).

About USAMRIID

USAMRIID, located at Fort Detrick, Md., is the lead medical research laboratory for the U.S. Biological Defense Research Program, and plays a key role in national defense and in infectious disease research. The Institute's mission is to conduct basic and applied research on biological threats resulting in medical solutions (such as vaccines, therapeutics and diagnostics) to protect the warfighter. USAMRIID is a subordinate laboratory of the U.S. Army Medical Research and Materiel Command.

The information contained in this press release does not necessarily reflect the position or the policy of the Government, and no official endorsement should be inferred.

About AVI BioPharma

AVI BioPharma develops therapeutic products for the treatment of life-threatening diseases using third-generation NEUGENE antisense drugs. 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 combat disease by targeting single-stranded RNA viruses, including West Nile virus, hepatitis C virus, dengue virus and Ebola virus. AVI has introduced a NEUGENE-based exon-skipping technology called ESPRIT therapy. 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.