Last checked at 
* Supply challenge after green light to use unproven drugs
* Race to scale up production, testing of Ebola treatments
* Two vaccines set to enter clinical trials in coming weeks
By Ben Hirschler
LONDON, Aug 12 (Reuters) - World Health Organization expertsfighting the world's worst outbreak of Ebola hope for improvedsupplies of experimental treatments and progress with a vaccineby the end of the year.
That may come too late to put an end to the currentepidemic, which is more likely to be stopped by standardinfection control measures, but it offers hope for the nextinevitable outbreak.
After ruling on Tuesday that it is ethical to offer unprovenEbola drugs to people infected or at risk in West Africa, thechallenge is to secure enough doses to make a difference in anoutbreak that has already claimed more than 1,000 lives.
An experimental drug called ZMapp from U.S. firm MappBiopharmaceutical appears to have had "a dramatic and very rapideffect" in the case of two U.S. doctors, WHO assistantdirector-general Marie-Paule Kieny told reporters.
However, the scant supplies of this drug are now effectivelyexhausted, after Liberia secured doses for two of its doctors.Spain's Health Ministry said a 75-year-old Spanish priest, theonly other person known to have been given ZMapp, had died.
One of the deadliest diseases known to man, Ebola kills thevast majority of those infected. Its symptoms include internaland external bleeding, diarrhoea and vomiting.
Other drugs are also at an early stage of development,including a treatment from Tekmira Pharmaceuticals thatwas cleared last week by U.S. regulators for testing in infectedpatients.
None of these, however, is available in the quantitiesneeded to make a dent in the West African epidemic - even ifthey work as well as hoped.
Still, the WHO is optimistic supplies can be ramped up byaround the turn of the year, although the number of dosesavailable will likely still remain insufficient to meet demand.
The United Nations agency also believes a vaccine can befast-tracked for use in those most at risk, such as healthcareworkers caring for patients, laboratory technicians and peopleburying the dead.
Kieny said two vaccine candidates were set to enter clinicaltrials in the coming weeks and there could be enough early-stagedata to consider their emergency use by the end of 2014.
"We could have enough information, very preliminary, butmaybe enough information on their safety in humans by the end ofthe year," she said. "There is a way to fast-track clinicaltrials."
The two vaccines due to enter the first phase of humantesting have been developed by GlaxoSmithKline andProfectus Biosciences.
MARKET FAILURE
Normally, it takes many years to test a new drug or vaccineand determine it is safe for use, so the bar will be loweredsignificantly in the case of Ebola. That worries some experts.
"So far these therapies have been tested only in a handfulof monkeys," said Kevin Donovan, director of the Center forClinical Bioethics and a professor of paediatrics at GeorgetownUniversity, speaking on a panel convened on Tuesday by theO'Neill Institute for National and Global Health Law.
"We don't know what harm they will do over the long term oreven the short term. We owe it to the Ebola victims, current andpotential, to get this right."
The decision to support the use of unproven treatmentsreflects the deadly nature of the disease and the need to closethe research gap left by the pharmaceutical industry's failureto tackle a neglected tropical disease found in poor countries.
"The fact that there is currently no registered drug forEbola is a market failure," Kieny said. "If it hadn't been forthe investment of a few governments into the development ofthese drugs and vaccines, we would be nowhere."
There has been an outbreak of Ebola every few years sincethe virus was first discovered nearly 40 years ago in theforests of central Africa.
But it is only in the past 10 years or so that researchers -prompted in part by the perceived bioterror threat posed byEbola - have started to look seriously at the disease,generating the current range of potential drugs and vaccines.
(Additional reporting by Kate Kelland, Stephanie Nebehay andToni Clarke; editing by David Clarke)
