​One Ebola drug tapped out after experimental doses

In the battle against the Ebola outbreak, the experimental treatment ZMapp had offered hope, but its manufacturer now says its supply has been exhausted.

Manufacturer Mapp Biopharmaceutical told Bloomberg News that it is bringing "additional resources" to scale up production, but that its stores of the treatment have been depleted after sending the drug to Africa. The drug was provided at no cost, it said.

Nigeria and Liberia are among the countries that had requested the treatment, with the company telling Bloomberg it had complied with every request for the drug that was authorized by legal and regulatory authorities. The treatment was given to the two American aid workers who have since been transferred to Emory University Hospital in Atlanta, and a Spanish missionary priest, who died Tuesday.

"It is our understanding that all patients offered treatment, treated, or expected to be treated were or are highly capable of providing informed consent for the use of an experimental drug not yet evaluated for safety in animals or people," the company said in a statement.

ZMapp is an antibody cocktail, but not much is known about whether it works, The Associated Press reports. One study found that 43 percent of monkeys treated with ZMapp survived after they showed Ebola symptoms.

Mapp didn't disclose which countries had been given its remaining doses, Bloomberg notes.

While there's no approved treatment for Ebola, another company, Tekmira Pharmaceuticals (TKMR) is also working on a treatment called TKM-Ebola. The U.S. Food and Drug Administration on Thursday said it would modify an earlier halt on testing the treatment, allowing infected patients to receive the medication.

Tekmira didn't immediately respond to a request for information about how much of a supply it has on hand.

The chief medical officer for Sierra Leone, which has been hit with the outbreak, told Bloomberg it has asked Tekmira about gaining access to the treatment. The official also said it was waiting on an outcome of a World Health Organization panel about using the experimental drugs before seeking ZMapp.

The small supply of available treatments is creating tough questions, Bloomberg notes.

"The more recently you've been infected, the more likely you'll respond better than if you're 20 days out," Arthur Caplan, the director of medical ethics at NYU Langone Medical Center, told the publication. "How about young versus old? Do we care if you're 10 or if you're 80?"