SAN DIEGO — As the fast-moving Ebola virus sweeps through eastern Congo, scientists are braving war zones hoping to test new medicines on sick patients there.

Despite civil unrest in the region, Doctors Without Borders has set up testing sites in the cities of Butembo and Beni, the latest hot spots of the current Ebola outbreak in the Democratic Republic of the Congo. But researchers have plans to chase the virus as it moves throughout the region, which it does at a rather rapid pace.

Here in San Diego, where scientists have long been studying the deadly virus, a biotech company is getting a rare shot at seeing how its drug compares to three other experimental treatments that are part of this trial, including ones made by biotech giants Regeneron and Gilead Sciences.

The San Diego firm — Mapp Biopharmaceutical — leaped into national news in 2014, when its experimental medicine, ZMapp, was used during the West African Ebola epidemic. The drug is a mixture of three antibodies meant to knock down levels of the Ebola virus in the body, hopefully buying time for the patient’s immune system to rally and defeat the disease.

Anecdotal accounts indicated ZMapp might have helped save the lives of infected patients such as American missionaries Dr. Kent Brantly and Nancy Writebol.

ZMapp spiked in demand during the 2014 outbreak, but the company wasn’t set up to make its drug at mass scale back then. By early 2015, when a clinical trial was finally authorized to start treating patients with ZMapp, the epidemic was waning. The study moved forward anyway but had a hard time recruiting patients to test. In the end, the data showed some evidence ZMapp helped Ebola patients survive. But not enough patients were enrolled in the trial for the drug to prove statistical significance.

Of course, fewer grievously ill people is a good thing. But it’s hard to test whether a drug works when proper trials can’t be conducted.

“It’s challenging to do clinical trials in a way that will satisfy (regulators) because we obviously would never intentionally infect people with Ebola,” said Larry Zeitlin, founder and president of Mapp Biopharmaceutical.

And so data on ZMapp — and other newer drugs designed to fight the virus — are slim. And that means scientists must rely on animal trials to learn how Ebola reacts to drugs, which can be a hindrance to understanding the virus.

This is why researchers are rushing into regions of eastern Congo to set up new trial sites at area hospitals where outbreaks arise, despite the political unrest in the area. The National Institutes of Health is leading the trial, and it’s overseen by a World Health Organization steering committee, along with other national and international actors.