The head of WHO, Tedros Adhanom-Ghebreyesus, said: "We can now offer patients an even better chance of survival."
Two vaccines against the deadly Ebola virus have recorded significant surviving rates in the Democratic Republic of the Congo (DRC), where the disease has claimed more than 1,800 lives over the past 12 months.
The World Health Organisation and the US National Institutes of Health announced on Monday that two out of four vaccines against Ebola being tested as part of a trial in the DRC had been dropped but that the remaining two had shown great promise with a survival rate of as much as 90%.
The two experimental drugs - Regeneron's REGN-EB3 and a monoclonal antibody called mAb114 - were both developed using antibodies harvested from survivors of Ebola infection.
The treatments are now going to be offered to all patients in the Democratic Republic of Congo (DRC), according to U.S. National Institute of Allergy and Infectious Diseases.
During the study — in which 681 people have so far taken part in since it began in November 2018— 29% of the patients on REGN-EB3 died while 34% of those on mAb-114 did. The other two drugs being tested — ZMapp and remdesivir — had rates of 49% and 53% respectively.
Anthony Fauci, director of the U.S. National Institute of Allergy and Infectious Diseases, told reporters in a telebriefing the results were "very good news" for the fight against Ebola.
"What this means is that we do now have what look like (two) treatments for a disease for which not long ago we really had no approach at all," he said.
The agency said of the patients who were brought into treatment centres with low levels of virus detected in their blood, 94% who got REGN-EB3 and 89% on mAb114 survived.
In comparison, two-third of the patients who got remdesivir and nearly three-fourth on ZMapp survived.
The head of WHO, Tedros Adhanom-Ghebreyesus, hailed the results as "welcome news."
"We can now offer patients an even better chance of survival," he added.
Mike Ryan, head of the WHO's emergencies programme, said the trial's positive findings were encouraging but would not be enough on their own to bring the epidemic to an end.
"The news today is fantastic. It gives us a new tool in our toolbox against Ebola, but it will not in itself stop Ebola," he told reporters.
More than 2,800 cases of Ebola have been reported and 1,888 people have died in DRC since August 2018, in what has become the second-largest outbreak on record, according to WHO. Almost one in three cases is a child.
The response to the epidemic has been hampered by violence, including attacks on humanitarian and medical personnel, prompting the UN Security Council to call "for an immediate cessation of hostilities by all armed groups" earlier this month.
A vast Ebola outbreak in West Africa become the world's largest ever when it spread through Guinea, Liberia and Sierra Leone from 2013 to 2016 and killed more than 11,300 people.