What to Know About the Experimental Drug Being Given to the Texas Ebola Patient

— -- Thomas Eric Duncan, the first Ebola patient to be diagnosed on American soil, will be receiving an experimental drug called brincidofovir, but the drug has yet to be tested for effectiveness against Ebola in humans or monkeys.

Though brincidofovir has been tested in humans against other viruses, it has only been tested against Ebola in small cell studies. But those studies -- which were done in partnership with the National Institutes of Health and the U.S. Centers for Disease Control and Prevention -- were promising, the company said.

Brincidofovir is an oral antiviral drug made by a small North Carolina drug company called Chimerix, which has been working on the drug for the past 14 years. The company claims the drug can fight off multiple viruses, including adenovirus and herpes simplex. It's also been studied against smallpox as part of a partnership with the National Institute of Asthma and Infectious Diseases.

The company announced today that through the Food and Drug Administration's expanded access program, it had been authorized to provide brincidofovir to multiple Ebola patients. This is not a blanket authorization, but rather several case-by-case authorizations brought on by physicians who requested the drug, according to FDA rules. The company did not say how many patients would be getting it, and the FDA said it cannot comment on unapproved drugs.

Duncan is currently listed in critical condition at Texas Health Presbyterian Hospital in Dallas. The hospital said today that he began receiving the drug on Saturday.

This is not the first time brincidofovir has made national headlines. Earlier this year, the unapproved drug was credited with helping save 8-year-old Josh Hardy, who in March was fighting to survive an adenovirus -- a common virus that causes colds but can also be much more serious.

The Hardys were sure the drug was the only thing that would save their son, but Chimerix at first refused to give it to him, citing supply concerns because they would have to give it to hundreds of other children if they gave it to Josh. But his story accelerated talks with the FDA, prompting the development of a 20-patient clinical trial. Josh got the drug, and after six and a half months in the hospital, went home in mid-July.

Read More About Josh's Story

Chimerix said it was working with the FDA to finalize a clinical trial protocol to test brincidofovir in Ebola patients "early this week."