Acambis Smallpox Vac Trials
Suspended Over Side-Effects

By Jim Armitage
Evening Standard - London
From ProMED-mail
Acambis, the Cambridge-based drug company that supplies the US government with smallpox vaccines to protect the population against biological attack, today suspended trials of the [vaccine] after finding serious side-effects among some volunteers. With the US on high terrorist alert, it fast-tracked orders for 209 million doses of the [vaccine] from Acambis before it had been fully tested. Now, intense monitoring has discovered that some of those [who participated] in the trials suffered a major heart condition. The drug has not been given to anybody outside the trials.
Acambis, headed by chief executive Gordon Cameron, is one of many drug companies attempting to make a safer version of the only licensed existing vaccine, Dryvax, which has been used for generations. Despite its efficacy, Dryvax's manufacture, prepared from [lymph collected from lesions on] calves' bellies, is seen as dated.
The company's Acam2000 is a chemically produced version of the vaccine given by injection. [The ACAM1000 vaccine, to which it is presumed ACAM2000 is related, is a live attenuated cell culture-produced vaccine derived from the Dryvax original - see below]. Acambis was one of the companies that lost out in the bidding for the contract to provide vaccines for the United Kingdom. That deal was controversially won by PowderJect, whose founder Paul Drayson was a major Labour Party donor.
Smallpox was eradicated in 1971 after a worldwide Dryvax vaccination and quarantine programme organised by the World Health Organisation. But the threat of [the use of smallpox virus] as a biological weapon by rogue states and terrorists has led most 1st-world governments to stock up on unlicensed vaccines to give to the public in the event of an attack. The military and front-line medical workers vaccinated since 9/11, considered most likely to come into contact with the disease, have been given Dryvax from old stock.
As part of its contract with the US, Acambis was [required] to [submit] the new vaccine to the normal trials required for other [vaccines] and to [verify] that it was as effective as Dryvax, its predecessor. The problems now appearing in the Phase III trials were anticipated, because heart conditions had been noticed in previous Dryvax vaccination programmes. It is unclear whether the findings reported today are [attributable] to the intensive monitoring now being conducted into Acam2000 or the product itself.
[A description of the derivation of the Acambus 1000 vaccine can be found in an article in the issue of Nature Medicine for 9 Sep 2003 (Nat Med. 2003 Sep;9(9):1115-6.), entitled: "Clonal vaccinia virus grown in cell culture as a new smallpox vaccine". Briefly, in order to develop a modern smallpox vaccine, vaccinia virus was derived from the existing Dryvax vaccine by adaptation for growth in a human diploid cell line. 6 cloned and one uncloned vaccine candidates were produced. One clone, designated ACAM1000, was chosen for development based on its comparability to Dryvax when tested in mice, rabbits, and monkeys for virulence and immunogenicity. By most measures, ACAM1000 was less virulent than Dryvax. We compared ACAM1000 and Dryvax in a randomized, double-blind human clinical study. The vaccines were equivalent in these initial trials in their ability to produce major cutaneous reactions ('takes') and to induce neutralizing antibody and cell-mediated immunity against vaccinia virus.
It remains to be established whether the cell culture-derived and -produced vaccine is inferior to Dryvax, or whether the stringency of the phase III trials procedure has been increased in the light of more clinical assessment of the performance of the Dryvax vaccine. - Mod.CP]
Patricia A. Doyle, PhD Please visit my "Emerging Diseases" message board at: Zhan le Devlesa tai sastimasa Go with God and in Good Health



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