(Adds details of drugs in development, reaction from experts)
GENEVA/LONDON Aug 6 (Reuters) - The use of an experimental drug on two U.S. charity workers with the deadly Ebola virus has prompted the World Health Organization (WHO) to consider the implications of making such treatments more widely available, it said on Wednesday.
The Geneva-based agency, which is hosting a two-day Emergency Committee of experts to decide on the international response to the disease that has killed nearly 1,000 people in West Africa, said it would convene a meeting of medical ethics experts early next week.
"We are in an unusual situation in this outbreak. We have a disease with a high fatality rate without any proven treatment or vaccine," WHO Assistant Director-General Marie-Paule Kieny said in a statement. "We need to ask the medical ethicists to give us guidance on what the responsible thing to do is."
Health experts and specialists on viruses and infectious diseases welcomed the WHO's decision to consider the problem, but warned it would not be easy.
"Giving unlicensed and untested treatments and vaccines is a very thorny ethical issue," said Jonathan Ball, a professor of molecular virology at Britain's University of Nottingham.
"One could argue that the current outbreak provides a perfect arena in which to test new drugs, but that isn't without risk. We don't know their safety, we don't know if they are likely to work - sure they have been tested in animals but these studies don't always tell us what will happen in humans."
The gold standard for assessing new medicine is a series of trials in humans, starting small to make sure the medicine is safe to use. The WHO's statement noted that medicine's guiding principle is "do no harm".
There is no registered medicine or vaccine against Ebola and the pipeline of drugs in development is far from bulging - partly due to a lack of research money for a medicine likely to be used mainly in poor countries with scant healthcare funds.
But several small biotech companies and U.S. universities are researching Ebola treatments, and Tekmira Pharmaceuticals started initial Phase I trials of an experimental injectable drug in January.
U.S.-based Inovio and privately owned Vaxart are among those with experimental vaccines in animal testing, while GlaxoSmithKline last year acquired Swiss vaccine firm Okairos with an early-stage Ebola product.
The treatment given to the two U.S. medical workers consists of proteins called monoclonal antibodies, or "plantibodies", that bind to and inactivate the Ebola virus. It had only previously been tested in laboratory animals.
WHO has been criticised for a slow response to the outbreak, which is by far the most deadly and widespread in the almost four decade history of the disease. The death toll in the four West African countries hit by Ebola since February stood at 932 by Aug. 4, with a total of 1,711 cases.
On Tuesday, three of the world's leading Ebola specialists called for experimental treatments to be offered to others.
They said the WHO was "the only body with the necessary international authority" to allow such experimental treatments and it "must take on this greater leadership role".
Last month, one the three experts, Jeremy Farrar, a professor of tropical medicine and director of influential Wellcome Trust charity, told Reuters that at that stage in the outbreak "not a single individual has been offered anything beyond tepid sponging and 'we'll bury you nicely'".
Farrar said the WHO's move on Wednesday was a "very welcome step in the right direction".
"We must also remember that while we can likely provide safety data (on experimental medicines) from anywhere in the world, we can only assess whether a vaccine or drug works for Ebola by using it in affected countries with the consent of individuals and communities concerned," he said in a statement.
The WHO gave no details of how or when the experts' decision would be made public. (Editing by Louise Ireland)