Vaxart Demonstrates Efficacy of Oral Avian Flu Vaccine in Preclinical Studies

Saturday, October 25, 2008 General News
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SAN FRANCISCO, Oct. 24 Vaxart Inc., a biotechnologycompany focused on the development of oral vaccines, today announced positiveefficacy results from preclinical studies of the company's oral avian fluvaccine. Sean Tucker, PhD, Vaxart founder and vice president of research,presented data from animal models demonstrating that an orally administeredflu vaccine was protective against lethal exposure to H5N1 influenza. Tuckerpresented the data this morning at the Modern Mucosal Vaccines, Adjuvants &Microbicides (MMVAM) international conference in Porto, Portugal.

Delivery of flu vaccine via a capsule rather than an injection offerscritical advantages, particularly in the case of a pandemic. The Vaxartvaccine formulation can withstand ambient temperatures, enabling emergencydistribution methods that avoid the transmission risks associated withcentralized vaccination clinics. In the developing world, where medicalproviders and supplies are scarce, oral vaccination will reduce costs, as wellas needle reuse and consequent cross-infection.

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

"Injected vector-based vaccines that deliver a target pathogen proteinhave shown excellent potency in animal models, but their application has beenlimited in humans because the immune system typically responds to the vectorrather than the target," said Dr. Tucker. "By using oral delivery of a non-replicating vector with a potent adjuvant, we achieve a robust immune responsethat is focused on the targeted pathogen rather than the delivery vehicle.This approach addresses the problems that have plagued vector-basedvaccination and also allows us to create different vaccines simply byswitching out the antigen."

In the recent study, Vaxart tested the ND1 vaccine using oraladministration to ferrets, widely recognized as the most predictive animalmodel for influenza research. Researchers administered vaccine at the start ofthe study and at 4 weeks. At 8 weeks, researchers measured antibody responses,then monitored survival following direct nasal exposure of 10 times the medianlethal dose of H5N1 avian influenza virus. Seventy-five percent (6 of 8) oforal vaccinated ferrets developed antibody levels of 1:200 or greater,survived the challenge and were healthy as demonstrated by weight gain afterchallenge, while all 12 control ferrets either died (67 percent) or becamevery ill (33 percent). These results, if confirmed in human immunogenicitystudies, compare well to the approved, injectable avian flu vaccine thatachieved protective antibody levels in 45 percent of human subjects.

In a previous study conducted in mice, 6 of 6 mice vaccinated orally withND1 survived H5N1 avian flu challenge, while 8 of 8 unvaccinated mice died.Based on these results, Vaxart plans to proceed to an investigational new drugapplication (IND) and begin clinical studies of the avian flu vaccine in 2009.The company is also developing an annual flu vaccine.

"To date, efforts to develop a broadly-applicable oral vaccine platformhave not been successful, but the advantages of a modular approach for vaccinedevelopment are compelling, particularly for influenza," said Mark Backer, PhD,Vaxart CEO. "We can provide a vaccine that matches a new outbreak strainmonths faster than current approaches."

"These results are encouraging. An oral vaccine for pandemic flu would bea great help in rapid distribution to large numbers of people," said Dr.Arnold Monto, professor of epidemiology at University of Michigan. "Theavailability of an oral vaccine for annual influenza would also likely improvevaccination compliance and help reduce the rates of hospitalization and deaththat are associated with flu every year."

The Vaxart Approach

Vaxart has developed a proprietary, modular approach to vaccinedevelopment that will reduce the time and expense needed to bring new vaccinesto market. The key to Vaxart's efforts is a unique adjuvant (an adjuvant isthe vaccine component that enhances immune response to a foreign protein).Vaxart uses an adjuvant that works through a "toll-like receptor" (TLR).Vaxart determined that TLR3 is much more active in the gut than other TLRpathways that have been used for injected vaccines, making this the only TLRadjuvant approach likely to work well for oral vaccines. The company hasdemonstrated both the induction of mucosal immunity and the stimulation ofantigen-specific cell-based immunity following oral administration of itsvaccines; these features may provide a performance advantage over injectedprotein vaccines.

Another key feature of the Vaxart platform is the ability to employ thesame vector (delivery vehicle) across all vaccines. Typically an injectedvector can only be used once, because antibodies build up against the vectorproteins after initial exposure. Subsequent vaccines are less effective,because the body neutralizes the vector before a response can be mountedagainst the disease target. Vaxart has overcome this obstacle and demonstratedthat strong immune responses can be generated against multiple diseasesfollowing a series of different oral vaccines. Vaxart will be able to producenew vaccines through a standardized and low-cost process, and safety data fromone vaccine will be supportive for others created through the platform.

About Vaxart

Vaxart ( is a privately held biotechnology companyfocused on the development of oral vaccines. Vaxart's proprietary approach isideally suited for modular creation of vaccines, enabling the company toreduce development risk. Vaxart intends to apply its platform to develop afirst-in-class vaccine for pandemic influenza, as well as creating oralalternatives to current vaccines such as annual influenza and HPV. The companyexpects to begin clinical testing of its pandemic flu vaccine in 2009.Contact: Michele Parisi for Vaxart 925/864-5028

SOURCE Vaxart Inc.

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