LONDON -- GlaxoSmithKline PLC said it has begun human testing of two potential vaccines against the H5N1 strain of bird flu, with the aim of having a vaccine in production before the end of this year.
Glaxo is testing one shot in 400 healthy volunteers in Germany and the other in 400 healthy volunteers in Belgium. Both trials are evaluating the vaccines' safety and ability to boost a person's immune response against H5N1. Glaxo expects to have preliminary results from the trials in the third quarter. Regular seasonal flu shots don't protect people against H5N1.
Several drug companies and teams of government researchers have been racing in recent months to develop a shot that would protect humans from H5N1, which has killed 105 people over the past two years. Health officials are worried that H5N1 could mutate into a strain that would pass easily among humans, sparking a pandemic.
The world has a limited number of vaccine-production facilities, so most scientists are trying to invent a vaccine that could be stretched to more doses by adding a special booster called an adjuvant. The serum Glaxo is testing in Germany contains a classic type of adjuvant. In Belgium, Glaxo is testing a vaccine with a newer type of adjuvant that it hopes will have two benefits. First, it hopes the adjuvant will help stretch the vaccine to an even greater number of doses than a regular adjuvant would.
It also hopes the adjuvant will help protect people against a broader range of H5N1 strains. This is important because no one knows which exact form of H5N1 could emerge as the strain that causes a pandemic. If Glaxo can come up with a vaccine that protects against a wide range of virus strains, the shot could be given to people before a pandemic begins, Glaxo officials said.
Glaxo has already submitted a "mock-up" application to Europe's main medicines regulator, seeking broad-brush approval for a pandemic vaccine. Glaxo says this early application will speed ultimate approval if a pandemic virus emerges and if Glaxo invents an effective serum.
Earlier this week, researchers writing in the New England Journal of Medicine said that an experimental vaccine developed by the National Institute of Allergy and Infectious Diseases and Sanofi-Aventis SA proved effective in a human trial only at high doses, making it difficult to mass-produce in the event of a pandemic. In addition, two doses were needed to get the best result, and even then it only produced the desired immune response in 54% of the patients tested.
Chiron Corp. of Emeryville, Calif., and PowderMed of Oxford, England, are also working on bird-flu vaccines.
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