Acambis reports promising results for 'universal' flu vaccine

Editor’s Note: This article was modified Jan 8 to include more information about the Acambis preclinical study.

Jan 4, 2008 (CIDRAP News) – British technology company Acambis yesterday announced positive results for a phase 1 clinical trial of an influenza vaccine that it hopes could guard against seasonal and pandemic flu strains and end the need to reformulate the flu vaccine each year.

The vaccine, called ACAM-FLU-A, is designed to target all influenza A virus strains, Acambis said in a press statement yesterday. If clinical trials show the vaccine is effective, Acambis' product could represent major progress toward a universal flu vaccine that would protect against both influenza A and B. Type A influenza cases make up the majority of laboratory-confirmed flu cases in the United States each year.

The randomized, double-blind, placebo-controlled trial, conducted at multiple centers in the United States, involved 79 volunteers who received ACAM-FLU-A alone, the vaccine plus an aluminum hydroxide adjuvant, the vaccine plus QS-21 Stimulon, an investigational adjuvant, or placebo. Each volunteer received two doses, Acambis said in its press release.

Immune responses were seen in all groups, but the highest occurred in the group that received ACAM-FLU-A with the QS-21 Stimulon adjuvant. The company reported that 90% of the subjects in the group seroconverted. The trial also showed that the vaccine was well tolerated.

Acambis said that along with the phase 1 trial it also conducted a preclinical challenge study that evaluated ACAM-FLU-A's ability to protect against a 2004 Vietnam strain of H5N1 avian influenza. The press release did not specify what type of animal was involved with the clinical challenge test; however, an Acambis spokeswoman told CIDRAP News that the test was done on ferrets. The H5N1 virus was lethal in the group that received placebo, but 70% of the group vaccinated with ACAM-FLU-A were protected.

The company said it plans to submit the results for publication in the medical literature.

Frequent slight changes in flu viruses involve surface proteins hemagglutinin and neuraminidase, represented by H and N in virus names. These proteins enable flu viruses to enter host cells and then exit them after replication. H and N components are highly mutable, which means vaccine producers must adjust flu shot components each year to match circulating strains.

However, ACAM-FLU-A is a recombinant vaccine linked to a hepatitis B core that targets M2e, a conserved region of all influenza A strains, the company said.

Michael Watson, Acambis' executive vice president of research and development, said in the press release that M2e is one of the most discussed new approaches for influenza vaccination. "These are exciting data as they show that our ACAM-FLU-A can generate a robust M2e antibody response and that M2e-based vaccines can protect against H5N1 avian influenza," he said.

Acambis has said that it is looking for a similar conserved region on influenza B virus strains so that its vaccine can protect against all human seasonal flu strains, according to a previous CIDRAP News report.

Several other groups are investigating universal influenza vaccines, including the Wistar Institute in Philadelphia, Dynavax Technologies in the San Francisco area, and others.

See also:

Jul 30, 2007, CIDRAP News story "Acambis launches human trial of 'universal' flu vaccine"

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