BioWorld International Correspondent

LONDON - Acambis plc has won FDA approval for its smallpox vaccine ACAM 2000, the first new biodefense vaccine to be licensed since the U.S. government launched Project Bioshield in 2001.

Acambis previously supplied 192.5 million doses of the vaccine under the investigational new drug application, and the license paves the way for the company to agree to a deal with the Centers for Disease Control and Prevention (CDC) for a warm base manufacturing contract to maintain the stockpile.

Ian Garland, Acambis CEO, told BioWorld International that the granting of the license puts the Cambridge, UK-based company in a better position to complete negotiations with the CDC for the lucrative contract. However, he does not expect the marketing approval to lead to an immediate surge in sales of the vaccine.

Apart from the U.S., ACAM 2000 has been sold to 14 other governments. "The fact it is licensed may make a difference in some markets, but there are no contingent orders awaiting the approval," Garland said.

The warm base contract will require Acambis to keep its U.S. facility in readiness to manufacture ACAM 2000, but it is not clear how many doses the CDC will need to maintain the stockpile. One area of uncertainty is the shelf life of the vaccine, and another concerns the amount of product that likely would be consumed.

Military personnel are required to be vaccinated if they are posted to threat areas, and it is planned to switch from using the current Dryvax vaccine manufactured by Wyeth, of Madison, N.J., to ACAM 2000 now that it is licensed. Those doses will be supplied from the CDC's stockpile.

Garland also said the granting of the license may open the military market in other countries.

ACAM 2000 has an equivalent safety and efficacy profile to Dryvax, but is manufactured in cell culture using animal-free serum. The file on ACAM 2000 was reviewed by the FDA Vaccines and Related Biological Products Advisory Committee in May 2007, which voted 11-0 in favor of its safety and efficacy.

More than 3,800 subjects were vaccinated in two Phase III studies. One demonstrated noninferiority to Dryvax in producing a scab at the injection site in people not previously vaccinated against smallpox, a generally accepted surrogate endpoint. There was a 96 percent response in the ACAM 2000 group compared to 99 percent in the Dryvax group.

The second study demonstrated noninferiority to Dryvax in generating an immune response in subjects previously exposed to the older vaccine.