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Vaxart Reports Positive Data From Preclinical Studies of Oral Avian Flu Vaccine

Posted on: Tuesday, 28 October 2008, 06:00 CDT

Vaxart, a biotechnology company focused on the development of oral vaccines, has announced positive efficacy results from preclinical studies of the company's oral avian flu vaccine.

The data presented are from studies measuring the effectiveness of an orally administered avian flu vaccine designed by Vaxart scientists using the company's proprietary modular platform. The Vaxart vaccine (ND1) comprises a non-replicating chimeric adenovirus-5 vector, or delivery vehicle, engineered to express avian flu hemaggluttinin (HA) and a TLR3 ligand as a vaccine adjuvant.

In the study, Vaxart tested the ND1 vaccine using oral administration to ferrets, widely recognized as the most predictive animal model for influenza research. Researchers administered vaccine at the start of the study and at four weeks. At eight weeks, researchers measured antibody responses, then monitored survival following direct nasal exposure of 10 times the median lethal dose of H5N1 avian influenza virus.

Approximately 75% of oral vaccinated ferrets developed antibody levels of 1:200 or greater, survived the challenge and were healthy as demonstrated by weight gain after challenge, while all 12 control ferrets either died (67%) or became very ill (33%). These results, if confirmed in human immunogenicity studies, compare well to the approved, injectable avian flu vaccine that achieved protective antibody levels in 45% of human subjects.

Based on these results, Vaxart plans to proceed to an investigational new drug application (IND) and begin clinical studies of the avian flu vaccine in 2009. The company is also developing an annual flu vaccine.

Sean Tucker, Vaxart's founder and vice president of research, said: "Injected vector-based vaccines that deliver a target pathogen protein have shown excellent potency in animal models, but their application has been limited in humans because the immune system typically responds to the vector rather than the target.

"By using oral delivery of a non-replicating vector with a potent adjuvant, we achieve a robust immune response that is focused on the targeted pathogen rather than the delivery vehicle. This approach addresses the problems that have plagued vector-based vaccination and also allows us to create different vaccines simply by switching out the antigen."

Source: Datamonitor

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