Acambis reports successful phase I trial of cell-culture-grown smallpox vaccine

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Sep 5, 2002 (CIDRAP News) Ð The smallpox vaccine being produced by Acambis plc for the US government as part of the nation's bioterrorism preparedness program worked well in a Phase I trial, Acambis officials announced this week.

The vaccine, called ACAM1000, generated a characteristic skin lesion or "take" in all those vaccinated, and there were no serious or unusual side effects, the company reported in a Sep 3 news release.

ACAM1000 is grown in cell culture in a laboratory rather than on the skin of calves, the method used to produce nearly all smallpox vaccine in the past. Gordon Cameron, Acambis's chief financial officer in Cambridge, Mass., told CIDRAP News that to his knowledge, the phase I trial was the first successful trial of a cell-culture-derived smallpox vaccine. Acambis is based in Cambridge, England, but has US operations in Massachusetts.

The trial involved ACAM1000 and Dryvax, the vaccine that was widely used during the global campaign to eradicate smallpox, the company said. In the randomized, double-blind trial, 30 young adults received a standard dose of Dryvax and 30 received an equivalent dose of ACAM1000.

The primary end point of the trial was the appearance of a "take," which is the currently accepted indication of immunogenicity, the company said. "A 'take' was seen within 10 days after vaccination in100% of ACAM1000-treated subjects and 97% of Dryvax-treated subjects," the news release states. "The size and appearance of the 'takes' were identical across treatment groups. No serious or unexpected adverse events were reported in the ACAM1000 group, whereas one subject in the Dryvax group developed a non-healing pock at the site of inoculation."

The company said it has already begun a second trial, in which the vaccine's safety and immunogenicity will be tested in 70 people. Officials said Dr. Thomas Monath, Acambis's chief scientific officer, is scheduled to describe the results of the first trial today and tomorrow at a meeting of the G7 Global Health Security Action Group in Langen, Germany.

Acambis is producing ACAM1000 under a 54-million-dosecontract with the US Department of Health and Human Services (HHS); the contract originally was for 40 million doses but was expanded after the Sep 11attacks. The company also signed a separate contract in November 2001 to produce another 155 million doses of cell-culture-derived vaccine for HHS. HHS officials have said that with their existing vaccine stockpile and the new vaccine from Acambis, they expect to have enough smallpox vaccine for all Americans by the end of this year or early in 2003.

Cameron said Acambis hopes to be ready to apply for Food and Drug Administration approval of ACAM1000 in late 2003 or early 2004.

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