Ebola can no longer be called an incurable disease, scientists have said, after two of four drugs being trialled in the major outbreak in the Democratic Republic of the Congo were found to have significantly reduced the death rate.

ZMapp, used during the massive Ebola epidemic in Sierra Leone, Liberia and Guinea, has been dropped along with Remdesivir after two monoclonal antibodies, which block the virus, had substantially more effect, said the World Health Organization and the US National Institute of Allergy and Infectious Diseases, which was a co-sponsor of the trial.

The trial in the DRC, which started in November, has now been stopped. All Ebola treatment units will now use the two monoclonal antibody drugs.

“From now on, we will no longer say that Ebola is incurable,” said Prof Jean-Jacques Muyembe, the director general of the Institut National de Recherche Biomédicale in DRC, which has overseen the trial. “These advances will help save thousands of lives.”

One of the biggest obstacles in fighting the year-long DRC outbreak, the second biggest ever and now with 2,800 cases, has been the reluctance of those who fall sick to seek treatment.

It has not helped that the chances of survival have been low – up to 70% of those infected in the DRC have died. Muyembe said many people saw family members go into an Ebola treatment centre and come out dead.

“Now that 90% of their patients can go into the treatment centre and come out completely cured, they will start believing it and building trust in the population and community,” he said.

Anthony Fauci, the director of the US NIAID, said the overall mortality of those given ZMapp in the trial in four centres was 49% while that of Remdesivir was 53%. A monoclonal antibody drug made by Regeneron had the lowest overall death rate, at 29%, while the monoclonal antibody 114 made by Ridgeback Biotherapeutics had a mortality rate of 34%.

But the results in people who arrived at a treatment centre soon after they became sick, rather than staying at home, were even more impressive – with death rates of 24% on ZMapp, 33% with Remdesivir, 11% with 114 and just 6% with Regeneron’s drug.

On average, people who fall ill are not turning up at a treatment centre for four days, said Dr Michael Ryan from the World Health Organization. This reduces their chances of survival and makes it likely that the virus, spread through bodily fluids, will be transmitted to their families.

“The numbers might change,” said Fauci. “Not all the data has been accumulated.” The two monoclonal antibodies will both now be used in every treatment centre in DRC.

Fauci paid tribute to all of those involved in the trial in four towns: Beni, Katwa, Butembo and Mangina. NGOs including International Medical Corps and Médecins Sans Frontières “put their lives on the line every day to care for patients in extremely difficult conditions in the area where the outbreak is occurring,” he said.

Clinical trials in epidemic conditions are hard – even more so in Ebola outbreaks, where medical staff have to wear protective suits and all patients must be isolated.

“This trial – the first-ever multi-drug randomised trial for Ebola – has happened despite such highly complex and challenging circumstance,” said Dr Jeremy Farrar, the director of Wellcome and the co-chair of the WHO Ebola therapeutics group. “A long-running outbreak like this takes a terrible toll on the communities affected and it is a sign of just how difficult this epidemic has been to control that there have already been enough patients treated to tell us more about the efficacy of these four drugs.”

The trial will have saved lives, he said. The next phase should reveal more about which of the two works best in certain settings. “The more we learn about these two treatments, and how they can complement the public health response, including contact tracing and vaccination, the closer we can get to turning Ebola from a terrifying disease to one that is preventable and treatable. We won’t ever get rid of Ebola but we should be able to stop these outbreaks from turning into major national and regional epidemics,” he said.