Acambis plc has successfully completed a Phase I trial in its development of a vaccine against the virus that causes dengue fever. This initial Phase I trial tested in 56 healthy adult volunteers the safety, tolerability and immunogenicity of one of the four components in Acambis' ChimeriVax-Dengue vaccine. The component tested is known as ChimeriVax-DEN2 as it is targeted against the Dengue 2 serotype.
The trial incorporated several elements:
*a randomised, double-blind element in 42 volunteers compared the safety and immunogenicity of ChimeriVax-DEN2 at two dose levels with a licensed yellow fever vaccine, YF-VAX. All these volunteers had not previously had contact with yellow fever; and,
*an open-label portion of the trial included 14 volunteers who had previously received a yellow fever vaccine. They were vaccinated with ChimeriVax-DEN2 to test whether prior immunity to yellow fever would inhibit the response to ChimeriVax-DEN2. This is because the ChimeriVax technology from which ChimeriVax-DEN2 was developed employs an attenuated yellow fever virus as a backbone.
The preliminary findings from the trial are as follows:
* ChimeriVax-DEN2 was well-tolerated at the two dose levels tested;
* there were no serious adverse events;
* 100% of subjects developed neutralising antibodies to the homologous Dengue 2 serotype virus within one month of vaccination and 96% developed neutralising antibodies to a wild-type Dengue 2 virus;
*the seroconversion rate was similar at both dose levels tested; and
*prior immunity to yellow fever did not inhibit response to ChimeriVax-DEN2.
There are four immunologically related dengue virus serotypes, each of which needs to be represented in an effective vaccine. Acambis has successfully constructed vaccines against all four dengue virus serotypes and tested the immunogenicity, safety and efficacy of the tetravalent (four-component) vaccine in pre-clinical models. A Phase I trial of the tetravalent vaccine, ChimeriVax-Dengue, is planned for the first half of 2003.
Dr John Brown, Chief Executive Officer of Acambis, said, "Dengue fever is a major problem across the world, with an estimated 50 million cases every year. Development of an effective vaccine to prevent dengue fever is critical for the two-fifths of the world's population who are at risk from infection and these positive trial results represent a significant step along the road to achieving that goal."
The ChimeriVax-Dengue project is funded by Acambis' partner, Aventis Pasteur, who holds worldwide rights to sales of the vaccine.
A spokesperson for Aventis Pasteur commented, "From our Aventis Pasteur partnership perspective, these results further illustrate the attractiveness of the ChimeriVax technology for vaccine development. Aventis Pasteur is encouraged to press ahead with trials of the tetravalent ChimeriVax-Dengue."