Shares of Sarepta Therapeutics jumped 11 percent before the opening bell Friday after the drug developer said its potential Ebola treatment generated no safety concerns in early-stage human testing.

The drug has already shown in animal testing that it can prevent disease development or death following exposure to Ebola. Research in humans has just begun, however, meaning that it will likely be several years before federal regulators weigh approval of the drug.

The Cambridge, Massachusetts, company said Thursday that results from its study on healthy adult volunteers will be published in next month’s issue of the American Society for Microbiology.

Shares of Sarepta and other companies developing Ebola treatments have been sensitive in recent weeks to news of the disease’s outbreak, which has devastated West Africa. Shares of such drug companies jumped after the first case of the disease was diagnosed in the U.S.

The Ebola virus causes internal bleeding and organ failure and is fatal in 30 percent to 90 percent of all cases, depending on the strain. It spreads through direct contact with infected people. There is no vaccine and no cure.

The World Health Organization estimates that the death toll from the current outbreak in Africa will surpass 4,500 by the end of the week.

Shares of Sarepta Therapeutics Inc. rose $2.47 to $24.77 a couple hours before markets opened Friday. The stock climbed almost 7 percent Thursday and more than 10 percent Wednesday.