(787c) Development of a Scalable Process for Production of a Broadly Protective Influenza Antigen

While most influenza infections cause only mild illness, the World Health Organization (WHO) estimates that, on average, 3 to 5 million people worldwide develop respiratory or heart complications related to seasonal influenza infections each year. The WHO also estimates 250,000-500,000 influenza associated deaths yearly, with a large percentage occurring in developing world children with inadequate access to vaccines. Such mortality would be much worse for a virulent pandemic influenza strain. The current standard of care for influenza immunization is a trivalent whole-inactivated virus vaccine consisting of two influenza A strains (H1N1 and H3N2) and one influenza B strain. Due to antigenic drift, the influenza virus is constantly changing and experts must predict the dominant strains for the upcoming flu season roughly 7-9 months in advance of distribution. As a result, the actual circulating viruses may differ from those included in the vaccine, causing an increase in the number of influenza cases and the number of influenza-related deaths as was the case during the 2014-15 flu season. Once the three strains are selected, the majority of the vaccine is produced in eggs and treated for inactivation. This egg-based method takes roughly 6 months. As a result of the lengthy production times, vaccines cannot be updated to more accurately reflect the circulating strains in the case of a poor prediction.

A broadly protective influenza vaccine that would elicit strong protective responses for most or all possible circulating strains would dramatically reduce influenza-related hospitalizations and deaths by conferring life-long immunity. Our proposed vaccine would address many deficiencies in the current vaccine strategy by targeting a conserved region of the influenza hemagglutinin protein to protect against both seasonal and pandemic influenza strains. We will use a stabilized virus-like particle scaffold to present the antigen in a multivalent manner which more closely mimics the presentation of the antigen on the natural virus. By providing broadly protective immunity worldwide against seasonal and pandemic influenza, we would decrease the cost of medical care for influenza related illnesses, and dramatically reduce the number of influenza related deaths.

We have developed a stabilized hemagglutinin stem antigen which has the potential to provide broad protection against seasonal and pandemic strains of influenza. Here we discuss the development of a scalable refolding and formulation process for the production of our stabilized hemagglutinin stem antigen. By evaluating the kinetic and molecular forces required for the proper folding and trimerization of the hemagglutinin stem antigen, we have transitioned a number of lengthy, industrially unattractive refolding steps to a more reliable, scalable process. We are also working to further stabilize our hemagglutinin stem antigen for improved conformational stability with the ultimate goal of producing a cold-chain independent vaccine which would allow for improved distribution worldwide. We plan to evaluate both lyophilization and spray drying techniques for producing solid drug substance compatible with long term room temperature storage.