Baxter International Inc. has initiated a phase I/II clinical trial to test the company's vero-cell based candidate H5N1 pandemic influenza vaccine.

The study is being conducted with several hundred healthy adults in Austria and Singapore using the fully inactivated wild-type H5N1 strain A/Vietnam/1203/2004. Four different antigen concentrations ranging from 3.75µg to 30 µg are being tested in formulations with and without alum as adjuvant.

"We look forward to receiving clinical results this fall on the safety and immunogenicity of the candidate vaccine for pandemic flu," said Noel Barrett, vice president of Global R&D for Baxter's vaccines business. "Our goal is to produce a safe and efficacious pandemic vaccine and demonstrate the advantages that vero-cell based production can offer for manufacturing influenza and other vaccines. The study will provide us with critical data concerning the vaccine dosage required to induce protective immune responses, and information about the ability of a vaccine, based on a single H5N1 strain, to induce protective immune response against a range of different H5N1 strains. Preclinical studies in animal models have shown very good cross-protection to date, and we are looking forward to confirming this with studies in humans."

Baxter is developing both seasonal (or inter-pandemic) and pandemic influenza vaccines based on the company's proprietary vero-cell technology, which has the potential to significantly reduce production time compared to traditional vaccine production methods that use embryonated hens' eggs. The company is already licensed to produce vaccines at its commercial scale cell-culture vaccine manufacturing facility in Bohumil, Czech Republic, which is GMP approved and fully validated to Biosafety Level Three (BSL-3).

Cell-based systems for production of vaccines offer a number of potential benefits over more traditional egg-based systems. Baxter's vero-cell technology is capable of producing high yields of influenza virus without the addition of any animal-derived serum. Through the company's research and development work, Baxter has been successful in growing wild-type virus at pilot and commercial scales using its unique vero-cell technology. This means the company is currently capable of manufacturing pandemic vaccine without having to wait for high-growth or attenuated virus reassortants normally used when vaccine is produced in eggs. The requirements for such reassortants may involve considerable delay in vaccine production in the event of a pandemic.

In addition, Baxter is working with the US National Institute of Allergy and Infectious Diseases (NIAID), in partnership with Fisher BioServices Inc., and with the US Department of Health and Human Services in partnership with DVC LLC, a Computer Sciences Corporation Company, to develop vero-cell based H5N1 pandemic and seasonal influenza candidate vaccines. Both collaborations are the result of US Government contract awards. Baxter and its partners will be providing the vero-cell based candidate vaccines to the agencies for further clinical testing in the United States, which is expected to begin later in 2006 and 2007. Baxter is currently in discussions with several other governments regarding its candidate pandemic vaccine, and has been awarded a contract to supply two million doses of cell-culture based candidate H5N1 vaccine to the UK government.