Baxter Receives EMEA Positive Opinion for CELVAPAN, The First Cell Culture-Based Pandemic Flu Vaccine

Clinical data from a Phase III and subsequent booster study demonstrate safety, immune response and cross-protective memory

Thursday December 18, 2008, 5:03 pm EST

DEERFIELD, Ill.--(BUSINESS WIRE)--Baxter International Inc. (NYSE: BAX - News) today announced that the Committee for Medicinal Products for Human Use (CHMP) of the European Medicines Agency (EMEA) has issued a positive opinion for the marketing authorization of CELVAPAN, the first cell culture-based H5N1 (avian flu) pandemic vaccine, in the European Union.

The positive opinion precedes the licensure of the “mock-up” vaccine, which allows CELVAPAN to be used if the World Health Organization (WHO) officially declares a pandemic. The positive opinion was based on results from a comprehensive clinical development program, including a Phase III clinical trial that demonstrated vaccines for two different H5N1 virus strains were well tolerated and generated a functional immune response.

“We are very pleased to receive the EMEA’s positive opinion for CELVAPAN,” said Hartmut Ehrlich, M.D., vice president, BioScience global research and development. “This is another step towards our goal of supplying a safe and effective vaccine to protect the population against a possible influenza pandemic.”

A “mock up” vaccine is identical to the future pandemic vaccine in composition and manufacturing; however, since the actual pandemic strain is not known, the vaccine contains another influenza strain not yet exposed to the general population. Once a pandemic is declared, this licensure allows for a fast track approval of the vaccine containing the actual pandemic strain.

CELVAPAN is made using Baxter’s proprietary Vero cell technology, which offers advantages against conventional egg-based vaccine technology. Baxter’s Vero cell manufacturing process is more rapid due to its ability to use the “native” virus that does not need to be modified in order to grow in chicken eggs. The shorter time for vaccine production is critical in accelerating vaccine supply in response to an influenza pandemic.

CELVAPAN is produced in Bohumil, Czech Republic, at one of the largest cell culture vaccine production facilities in the world. Vero cell technology uses a well-established continuous mammalian cell line to produce the pandemic vaccine.

Baxter’s candidate avian flu vaccine is derived from the H5N1 strain A/Vietnam/1203/2004. Its antigen composition and structure are identical to the actual virus circulating in nature. This vaccine formulation alleviates the need to enhance the immune response by including adjuvants (additives) that may cause side effects. In the Phase III study, CELVAPAN induced an immune response that is similar to the body’s defense against a natural influenza virus infection.

Phase III Clinical Trial Results

The purpose of the randomized Phase III study was to evaluate safety and immune responses to 7.5 µg of the Vietnam strain vaccine in two age groups (adults 18-59 and elderly, i.e., older than 60). The antibody persistence and immune response to a booster with either the same or a different strain was also measured. The study also investigated the ability of the vaccine to induce cross-immunity against divergent H5N1 strains.

Overall, the vaccine was well tolerated after the first and second vaccination as well as after the booster, with a safety profile similar to currently licensed seasonal influenza vaccines. The most common side effects were injection site pain and headache, fatigue or malaise.

A positive immune response was induced even after only one immunization as determined by measurement of functional antibodies using a microneutralization assay (50.7 percent in the adult group; 54.4 percent in the elderly group). Following the second immunization, 73 percent of subjects in the adult and 74 percent in the elderly age group demonstrated seroneutralizing levels of antibody, meaning the vaccine was found to be at least equally immunogenic in the elderly as in the adult age group. A six-month booster vaccination with either A/Vietnam/1203/2004 or A/Indonesia/05/2005 strain vaccines induced a substantial booster response. A booster vaccination using a different strain resulted in high levels of antibodies against the initial and the booster strain, which is indicative of cross-protective immunological memory.

Last June, The New England Journal of Medicine published data demonstrating CELVAPAN met Phase I/II trial endpoints for safety and immunogenicity (generating a functional immune response). This was the first peer-reviewed publication of study results for CELVAPAN, the first cell culture-derived avian influenza vaccine to undergo clinical evaluation.

About Pandemic Flu

A pandemic is a global disease outbreak caused by an agent for which there is little or no immunity in the human population and which can spread easily from person-to-person worldwide causing serious illness and death. Most cases of avian flu infection in humans have so far resulted from direct or close contact with infected poultry (e.g., domesticated chicken, ducks, and turkeys) or surfaces possibly contaminated from feces of infected birds. Avian influenza infection follows an unusually aggressive clinical course, with rapid deterioration and a high fatality rate.

About Baxter

Baxter International Inc. develops, manufactures and markets products that save and sustain the lives of people with hemophilia, immune disorders, infectious diseases, kidney disease, trauma, and other chronic and acute medical conditions. As a global, diversified healthcare company, Baxter applies a unique combination of expertise in medical devices, pharmaceuticals and biotechnology to create products that advance patient care worldwide.