Epidermal DNA flu vaccine shows promise in phase 1 trial

Jun 2, 2006 (CIDRAP News) – An experimental DNA-based flu vaccine that is propelled into the skin on tiny particles instead of injected showed promise in a phase 1 trial involving 36 adults, according to a report published in the May 22 issue of Vaccine.

All volunteers who received a 4-microgram (mcg) dose of the vaccine had a sufficient immune response at 21 days, according to the study. The DNA vaccine, developed by the biotech firm PowderMed of Oxford, UK, contains the hemagglutinin gene from a 1999 Panama strain of influenza A(H3N2).

"This study is the first successful demonstration of immunogenicity of an influenza DNA vaccine in humans," said senior author Hansi J. Dean, PhD, of the University of Wisconsin School of Medicine and Public Health in a May 31 PowderMed press release.

Researchers divided the study participants (aged 19 to 50; mean, 31) into three groups of 12, with each group receiving one dose of either 1, 2, or 4 mcg of the vaccine. Vaccines were administered using a PowderJect XR-1 device, which employs pressurized helium to propel gold particles coated with plasmid DNA into the epidermis, according to the PowderMed Web site.

At 21 days, only the 4-mcg group met one of the criteria for immune response used for vaccine licensure by the Committee for Proprietary Medical Products (CPMP) in the European Union. By day 56, the 4-mcg group met all three immune-response criteria, even though only one criterion is required to meet CPMP standards.

By day 56, 64% (7/11) of patients in the 4-mcg group seroconverted, and 100% (11/11) achieved seroprotection, defined as an antibody titer of 40 or greater.

Neither of the lower-dose groups met CPMP standards for antibody response by day 21, but both groups had by day 56. The 2-mcg group met all three criteria by day 56, while the 1-mcg group met one criterion.

In addition, no volunteer reported serious side effects. Twenty-seven of the 36 participants reported mild to moderate local adverse events, and 23 reported mild to moderate systemic adverse events.

The study authors concluded, "While the results of this study are promising, further development will be required for a commercially feasible DNA vaccine for influenza."

"DNA vaccines have the potential to significantly limit the burden of disease," said PowerMed CEO Clive Dix, PhD, in the press release. "The advantage of a DNA-based approach is that the vaccines can be manufactured very rapidly and in large quantities, while yielding an efficacious immune response at low doses."

In addition, according to a Reuters story published yesterday, the vaccine is stable and does not need to be refrigerated, or even administered by a healthcare professional.

PowerMed will begin phase 2 trials later this year using both avian flu and annual flu strains, according to the Reuters article. A marketable vaccine is years away, according to Reuters.

Drape RJ, Macklin MD, Barr LJ, et al. Epidermal DNA vaccine for influenza is immunogenic in humans. Vaccine 2006;24(21):4475-4481 [Abstract]

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