A new Ebola drug has cured monkeys infected with the virus, US researchers announced.
Experimental drug TKM-Ebola-Guinea targets the Makona strain of the virus, which caused the current deadly outbreak in West Africa.
All three monkeys receiving the treatment were healthy when the trial ended after 28 days.
Three untreated monkeys died within nine days.
However, scientists cautioned that the drug’s efficacy has not been proven in humans.
Currently there are no treatments or vaccines for Ebola that have been proven to work in humans.
Thomas Geisbert from University of Texas, who was the senior author of the study published in the journal Nature, said: “This is the first study to show post-exposure protection… against the new Makona outbreak strain of Ebola-Zaire virus.”
Results from human trials with TKM-Ebola-Guinea are expected in the second half of this year.
Thomas Geisbert said the drug, produced by Tekmira Pharmaceuticals, could be adapted to target any strain of Ebola and could be manufactured in as little as eight weeks.
TKM-Ebola-Guinea works by blocking particular genes, which stops the virus replicating.
The two-month production time compares with the several months needed to make ZMapp – another experimental drug, which cured monkeys with a different strain of Ebola than the one in the current outbreak.
Since March 2014, more than 10,602 people have been reported as having died from the disease in six countries – Liberia, Guinea, Sierra Leone, Nigeria, the US and Mali.
The total number of reported Ebola cases is more than 25,556.
A trial of brincidofovir – a potential drug to treat Ebola – has started at a Medecins Sans Frontieres center in Liberia.
The antiviral is being tested on Ebola patients on a voluntary basis. People who do not consent to it receive standard care.
Oxford University scientists leading the research say initial results are expected in the next few months.
A study involving a similar drug – favipiravir – began in Guinea in December.
More than 8,000 people have died from Ebola during this outbreak, the majority in the worst-affected countries of Guinea, Sierra Leone and Liberia.
While a handful of experimental drugs, including brincidofovir and favipiravir, have been given on an ad hoc, compassionate basis in the last year, none has yet been proven to work against the virus in scientific human trials.
A huge international effort – involving the WHO, MSF, drug companies, the Wellcome Trust, and other global health organizations – aims to fast-track treatments that have been identified as potential options.
Prof. Peter Horby, one of the chief investigators at Oxford University, said: “Conducting clinical trials of investigational drugs in the midst of a humanitarian crisis is a new experience for us all, but we are determined not to fail the people of West Africa.
“We are trying a number of different approaches simultaneously as there is only a short window of opportunity to tackle this virus during the outbreak.”
Scientists at Oxford say brincidofovir was chosen because it is effective against Ebola-infected cells in laboratories, has been deemed safe in more than 1,000 patients in trials against other viruses and can be given conveniently as a tablet.
Researchers aim to recruit more than 100 people and will compare death rates at the centre before and after the trial.
The other antiviral drug, favipiravir, being tested by the French National Institute of Health, is already used to treat influenza.
It is offered to all patients who receive care at the MSF treatment centre in Gueckedou, Guinea, and early results are expected in a few months’ time.
Scientists are testing other drugs and treatments.
Oxford University and the company Tekmira hope to establish a further study of a potential treatment which aims to interrupt the genetic code of the virus called TKM-Ebola.
Another approach is to use blood plasma from patients who have recovered from the disease. Trials of this are under way in Guinea’s capital, led by the Antwerp Institute of Tropical Medicine. This treatment is also being given to the British nurse Pauline Cafferkey in hospital in London.
And trials involving three separate vaccines designed to prevent people from getting the disease, are taking place in Switzerland, UK, US and Mali.
While a number of different pharmaceutical attempts are being made to tackle the Ebola virus, experts say other strategies – including early and adequate hydration and nutrition – are extremely important.
The World Health Organization (WHO) has announced that untested drugs can be used to treat patients infected with the Ebola virus.
The WHO said it was ethical in light of the scale of the outbreak and high number of deaths – more than 1,000 people have died in West Africa.
The statement was made after its medical experts met in Switzerland on Monday to discuss the issue.
However, officials warned there were very limited supplies of potential treatments.
The WHO said where experimental treatments are used there must be informed consent and the results of the treatment collected and shared.
The WHO says it is ethical to use untested drugs to treat patients infected with the Ebola virus
In a statement, it said: “In the particular circumstances of this outbreak, and provided certain conditions are met, the panel reached consensus that it is ethical to offer unproven interventions with as yet unknown efficacy and adverse effects, as potential treatment or prevention.”
However, the organization conceded there were still many questions to be answered including how data could be gathered effectively while the focus remained on providing good medical care.
It was also unclear where the funding for the treatment would come from.
Last week the WHO declared the Ebola outbreak was a global health emergency.
The move came as Liberia said it was getting an experimental drug, ZMapp, after requests to the US government.
The WHO said there were only 12 doses.
ZMapp has been used on two US aid workers, Dr. Kent Brantly and Nancy Writebol, who have shown signs of improvement, although it is not certain what role the medication played in this.
A Roman Catholic priest, infected with Ebola in Liberia, who died after returning home to Spain is also thought to have been given the drug.
However, the drug has only been tested on monkeys and has not yet been evaluated for safety in humans.
There is no cure for Ebola, which has infected at least 1,779 people since the outbreak was first reported in Guinea in February.
The Liberian government said it was aware of the risks associated with ZMapp, but the alternative was to allow many more people to die.