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* Drugmaker working on experimental vaccine with U.S. NIAID
* Phase I trial to start shortly but no guarantee of success
* GSK acquired vaccine after buying Swiss biotech Okairos
By Ben Hirschler
LONDON, Aug 10 (Reuters) - A clinical trial of anexperimental vaccine against the deadly Ebola virus is set tostart shortly, according to British drugmaker GlaxoSmithKline, which is co-developing the product with U.S.scientists.
The world's worst outbreak of Ebola has killed nearly 1,000people in West Africa and the disease could continue spreadingfor months, increasing pressure on researchers to acceleratetheir work on new medical interventions.
There is no proven cure or vaccine to prevent infection withEbola and the scale of the current outbreak has prompted theWorld Health Organisation to declare it an international healthemergency.
GSK's experimental vaccine has already produced promisingresults in animal studies involving primates and it is now dueto enter initial Phase I testing in humans, pending approvalfrom the U.S. Food and Drug Administration.
A company spokeswoman said on Sunday that the trial shouldget underway "later this year", while GSK's partner the U.S.National Institute of Allergy and Infectious Diseases (NIAID)said in a statement on its website it would start "as early asfall 2014", implying a potential September launch of testing.
Even if is fast-tracked, however, and emergency proceduresare put in place, the new vaccine could not be ready forwidespread deployment before 2015 - even assuming it works aswell as hoped.
"It is right at the beginning of the development journey andstill has a very long way to go," the GSK official said,declining to be drawn on a possible timeline for launch.
The investigational vaccine is based on a chimpanzeeadenovirus into which two Ebola genes have been inserted, whichmeans it contains no infectious Ebola virus material.Adenoviruses are best known for causing the common cold.
Once the vaccine enters a cell and delivers its geneticpayload, the two gene inserts produce a protein that generatesan immune response in the body - but the adenovirus carrying thegenes does not replicate further.
GSK acquired the vaccine after buying Swiss-based biotechcompany Okairos for 250 million euros ($335 million) last year.
The U.S. NIAID - part of the National Institutes of Health -is also supporting work on other early-stage Ebola vaccines,including one from Johnson & Johnson's Crucell unit thatshould enter Phase I clinical testing in late 2015 or early2016.
The Crucell vaccine is designed to give additionalprotection against Marburg, another severe and highly fataldisease caused by a virus from the same family as Ebola. ($1 = 0.7458 Euros) (Editing by Keiron Henderson)
