It would be unethical in drug trials to give placebos to people infected with the Ebola virus, experts have said.
The disease is so deadly, with a mortality rate as high as 70 percent, that doing so would amount to withholding "at least the possibility" of a cure, said the experts including Peter Piot, who co-discovered the Ebola virus in 1976.
Randomised control trials in which one group of people get the experimental drug and others a placebo or dummy drug, would not be ethical under the circumstances, they stated in a letter published by The Lancet.
Alternative trial designs already existed to find a working drug "more quickly, and with greatest social and ethical acceptability," the 17 health professionals and medical ethicists said.
Earlier this month, a letter in the Journal of the American Medical Association argued that randomised trials would help "maximise lives saved in the present epidemic and ensure knowledge gains for the next."
"We disagree," said the authors from Nigeria, Guinea, Ghana, Hong Kong, France, Britain, Uganda, Democratic Republic of Congo, Senegal and the United States in The Lancet.
"No-one insisted that Western medical workers offered ZMapp and other investigational products were randomised to receive the drug."
"None of us would consent to be randomised in such circumstances."
In cancers with poor prognosis, it is accepted that a promising new drug can be given to patients based on studies that did not have a control placebo group, with fuller analysis following later.
"The number one priority now is... to find out what works and what doesn't work in the fastest and most scientific way," co-signatory Piero Olliaro, a tropical disease expert and professor at Oxford University told AFP.
And there are ways of doing it that do not require the use of placebos, like "randomising patients with two things that work, not something that works and something that doesn't work."
Several trials were due to start in West Africa in the coming weeks.
Ebola has killed nearly 4,000 people mainly in Guinea, Liberia and Sierra Leone.
The World Health Organization gave the green light on August 12 for experimental treatments to be used in the outbreak, but there are limited stocks available.
The signatories of the letter said randomised trials could also pose practical problems and risked undermining public trust in Ebola treatment centres.
"It is also unclear that any capacity exists to impose controlled conditions during a raging epidemic," they said.