Researchers have stopped an experimental drug trial looking into potential treatments for Ebola on the grounds that it has been so successful. Two of the four medicines tested will now be administered to Ebola patients in the Democratic Republic of the Congo (DRC), health officials have said. 

The randomized trial began in November and has so far involved more than 600 people from the DRC, a country that is currently experiencing the world's second-biggest outbreak of Ebola ever recorded. 

Regeneron’s (REGN.O) REGN-EB3 and mAb114 (a monoclonal antibody) have both proven extremely effective, with more than 85 percent of people prescribed the drugs surviving if diagnosed early on in the disease's development.

While the data is still preliminary, officials have cautioned, survival rates for REGN-EB3 and mAb114 were 71 percent and 66 percent, respectively. What's more, when patients were admitted to the hospital with a low viral load and offered the drugs shortly after contracting the disease, their survival chances jumped to 94 percent (REGN-EB3) and 89 percent (mAb114).

In contrast, patients offered the other two drugs – ZMapp and Remdesivir – had a survival rate of 51 percent and 47 percent, respectively. That increased to almost three-quarters of patients prescribed ZMapp and two-thirds of patients prescribed Remdesivir, if diagnosed early.

According to the World Health Organization (WHO), the average fatality rate from Ebola is 50 percent, but it can vary on an outbreak-by-outbreak basis. In the past, rates have ranged from 25 percent to 90 percent. The DRC outbreak stands at 67 percent – as of August 4, 2019, 1,849 of the 2,763 Ebola cases (confirmed and probable) have ended in death. 

"From now on, we will no longer say that EVD (Ebola virus disease) is not curable," Jean-Jacques Muyembe-Tamfum, general-director of the DRC's federal medical research institute, told CNN. "This advance will, in the future, help save thousands of lives that would have had a fatal outcome in the past."

But others point out that these drugs in and of themselves might not be enough to stop the outbreak. 

"The news today is fantastic. It gives us a new tool in our toolbox against Ebola, but it will not in itself stop Ebola," said Mike Ryan, head of the WHO’s emergencies program, reports Reuters. 

Jean-Jacques Muyembe Tamfum, the director-general of the Institut National de Recherche Biomédicale (INRB) says he hopes it encourages people to bring in sick loved ones for treatment earlier rather than later, reports Nature. People frequently wait days after symptoms start before seeking medical attention.

While this is certainly exciting news, it is not the only recent medical development in the fight against Ebola – a WHO report published in April declared an experimental Ebola vaccine was 97.5 percent effective.