BioWorld International Correspondent

LONDON - Acambis plc said it has completed the manufacture of the first batch of 209 million doses of a new smallpox vaccine destined for the U.S. National Pharmaceutical Stockpile, and reported positive results in a second Phase I trial of the vaccine, ACAM 1000.

"We have gone from concept to vaccine in a bottle in about 10 months," CEO John Brown told a teleconference. "This was not a trivial task by any manner of means. It was a complex process involving a number of partner companies."

In the second, open-label Phase I trial of ACAM 1000, all 70 subjects developed protective immunity as indicated by the development of a pock mark on the skin at the site of inoculation. There were no serious adverse events. That reinforced results of the first double-blind trial in which 30 subjects were given ACAM 1000 and 30 Dryvax, the smallpox vaccine used during the worldwide smallpox eradication program.

In total, 100 previously unvaccinated subjects have now received ACAM 1000; all developed a pock mark, and there were no serious safety concerns.

"A Phase II study has been initiated and the program is going at a fair old pace," Brown said. The first Phase II subjects were inoculated last week.

The 209 million doses are covered by two contracts from the Centers for Disease Control and Prevention in Atlanta, and Acambis is developing two separate, but equivalent, vaccines, ACAM 1000 and ACAM 2000, for each contract. Acambis is required to manufacture for the stockpile and put the vaccines through clinical development simultaneously. The aim is to use modern cell culture manufacturing methods to produce a vaccine with equivalent efficacy to Dryvax.

Brown said the company has filed an investigational new drug application for ACAM 2000 and the Phase I trial will begin shortly. Phase III trials of both ACAM 1000 and ACAM 2000 are planned for 2003.

The vials of ACAM 1000 already submitted to the stockpile contain the same dose of vaccine as given in the Phase I trial, which also is the standard dose of Dryvax. Brown said the Phase II trial will involve dose ranging, but the evidence to date is that the dose in the completed vials is effective.

Acambis, based in Cambridge, said the FDA is being extremely supportive in helping it to finesse simultaneously manufacturing for the stockpile and expediting the clinical trials program. "This is a healthy and fruitful interaction, which is facilitating the smallpox project," said Chief Financial Officer Gordon Cameron.

The vaccines are being manufactured at Acambis' plant in Canton, Mass., which the company just spent US$40 million upgrading.