Acambis plc has commenced a Phase II clinical trial of its investigational MVA smallpox vaccine, MVA3000. Acambis is co-developing MVA3000 with its process development and manufacturing partner Baxter Healthcare SA.

MVA vaccines are a weakened form of smallpox vaccine. MVA3000 is being developed for use in people for whom the traditional smallpox vaccine is contraindicated, such as patients with disorders of the immune system or skin conditions such as eczema. The US Government plans to procure a stockpile of MVA as part of its defence against the threat of smallpox virus being used as a bio-terrorist weapon.

The Phase II trial is designed to gather further safety and immunogenicity data about MVA3000 when administered at three different dose levels. The randomised, double-blind, placebo-controlled study will involve 700 healthy adult subjects, half of whom have been previously vaccinated against smallpox, and is being conducted at up to 10 sites in the US. Data from this study will be used to select a dose of MVA3000 for further clinical testing.

In April, Acambis announced results from a Phase I safety and immunogenicity trial of MVA3000, in which 97% of subjects vaccinated at the highest dose level seroconverted to vaccinia virus-specific antibodies (determined by enzyme-linked immunosorbent assay) and 82% seroconverted to vaccinia neutralising antibodies (determined by plaque-reduction neutralisation testing) after two doses, according to a company release.

Acambis' Chief Executive Officer Gordon Cameron commented:
“The MVA3000 trial results to date have been exactly in line with our expectations of the vaccine's profile and we are confident this will continue in our Phase II trial. Under existing contracts with the US Government, we are also preparing for additional Phase I/II trials in target population subjects with HIV and atopic dermatitis and remain on schedule to commence these later this year.”