AVANIR's Investigational Anthrax Antibody Effective in Recognized Animal Model; UTMB Scientists Present Data at ASM Meeting

SAN DIEGO--(BUSINESS WIRE)--June 6, 2005--Data presented today at the 105th General Meeting of the American Society for Microbiology (ASM) described activity of AVANIR Pharmaceuticals' (AMEX:AVN) fully human monoclonal antibody treatment against inhalation anthrax. The data demonstrates that one dose (lowest dose tested was 1 mg/kg) of AVANIR's antibody, AVP 21D9, completely protected rabbits challenged with 100xLD50 dose of B. anthracis administered nasally. All animals, re-challenged three weeks later with anthrax but without additional antibody treatment, survived re-challenge as well. The data also showed that AVP 21D9 worked synergistically with the antibiotic Ciprofloxacin to protect mice and guinea pigs.

Johnny W. Peterson, Ph.D. of the University of Texas Medical Branch (UTMB) presented the results in a poster entitled "Human Monoclonal Anti-PA Antibody Completely Protects Rabbits and is Synergistic with Ciprofloxacin in Protecting Mice and Guinea Pigs Against Inhalation Anthrax" at the ASM meeting being held this week in Atlanta, Georgia.

"These data demonstrate that AVANIR's anti-PA human monoclonal antibody is very effective in protecting rabbits against anthrax spore challenge." said Dr. Peterson. "The rabbit model is one of the recognized models for determining efficacy of anti-anthrax antibodies. These data indicate that AVP 21D9 may provide the necessary immediate protection following anthrax exposure."

AVP 21D9 is a human monoclonal antibody to Bacillus anthracis protective antigen (PA) that was discovered and developed by AVANIR Pharmaceuticals. AVP 21D9 has demonstrated efficacy in protecting against anthrax in multiple experimental animal models. One molecule of the antibody is capable of neutralizing two anthrax toxin molecules in rat models. AVP 21D9 is the first antibody to demonstrate potency against a toxin at this "sub-stoichiometric" level.

"AVANIR's human monoclonal antibodies to PA have high specificity and very desirable binding properties, and offer considerable promise for the rapid development of products useful as therapy against the most lethal form of anthrax, inhalation anthrax," concluded Dr. Peterson.

The in vivo tests on passive immunization with AVANIR human monoclonal antibodies are being conducted in small animal models established at the University of Texas Medical Branch in Galveston under contract from the National Institute of Allergy and Infectious Disease (NIAID), a part of the National Institutes of Health.

Antibodies that neutralize anthrax toxins may augment existing treatment options. Currently, a vaccine and antibiotics are the treatment options available for the prevention or treatment of anthrax exposure. Both approaches have limitations. The current anthrax vaccine takes weeks following the first dose before immunity is established, and requires multiple injections over a period of months, in addition to annual boosters, to reach and maintain its protective effect. Antibiotics, the standard treatment of anthrax infection, are effective in killing anthrax bacteria, but have no effect on the anthrax toxins and require extended treatment for at least two months of twice daily dosing.

AVANIR Pharmaceuticals is a pharmaceutical company focused on developing and commercializing novel therapeutic products for the treatment of chronic diseases. AVANIR's product candidates address therapeutic markets that include central nervous system and cardiovascular disorders, inflammation, and infectious disease. AVANIR expects to submit the final module of its rolling new drug application to the U.S. Food and Drug Administration for its lead product candidate, Neurodex(TM), in mid-2005. Recently, AVANIR partnered its preclinical research and development program for inflammatory disease with Novartis. The Company's first commercialized product, Abreva(R), is marketed in North America by GlaxoSmithKline Consumer Healthcare and is the leading over-the-counter product for the treatment of cold sores. Further information about AVANIR can be found at www.avanir.com.

Except for the historical information presented herein, matters discussed in this press release contain forward-looking statements that are subject to certain risks and uncertainties that could cause actual results to differ materially from any future results, performance or achievements expressed or implied by such statements. Statements that are not historical facts, including statements that are preceded by, followed by, or that include such words as "estimate," "anticipate," "believe," "plan" or "expect" or similar statements are forward-looking statements. Risks and uncertainties for AVANIR Pharmaceuticals include risks associated with product discovery and development, our dependence on government grants to subsidize the development of our anthrax antibodies, as well as risks shown in AVANIR's most recent Annual Report on Form 10-K and Quarterly Report on Form 10-Q and from time-to-time in other publicly available information regarding the company. Copies of such information are available from AVANIR upon request. Such publicly available information sets forth many risks and uncertainties related to AVANIR's business and technology. Avanir's monoclonal antibody technology competes with several technologies used by large pharmaceutical and biotechnology companies and is subject to a number of uncertainties, including risks associated with the success of clinical trials, the progress of research and product development programs, the regulatory approval process, competitive products, future capital requirements and commercialization risks, particularly with drug candidates being developed for the U.S. federal government. There can be no assurance that such development efforts will succeed, that such products will receive required regulatory clearance, or that even if such regulatory clearance were received, that such products would ultimately achieve commercial success. The company disclaims any intent or obligations to update these forward-looking statements.

    CONTACT: AVANIR Pharmaceuticals
             Patrice Saxon, 858-622-5202

    SOURCE: AVANIR Pharmaceuticals