Two drugs approved by the U.S. Food and Drug Administration (FDA), better known for their ability to tinker with estrogen pathways, can also block dangerous Ebola virus infections in mice. The findings, published today in Science Translational Medicine, could lead to the first therapy for Ebola.

Ebola virus causes hemorrhagic fever, a devastating disease more famously known for its ability to cause bleeding in the eyes, nose, and GI tract. Although Ebola outbreaks are rare, they are highly dangerous, with up to 90 percent of its victims dying within one to two weeks. Currently there is no treatment that can stop the virus.

The two drugs in question — Clomid and Fareston — were stumbled upon by screening a library of 2,000 FDA-approved drugs to see if any could keep the virus from infecting cells in a petri dish.

Clomid (clomiphene) is prescribed as a therapy for female infertility, while Fareston (toremifene) is used for treating metastatic breast cancer.

The researchers found that both drugs could rescue mice from Ebola infection. Clomid was the better of the two, saving 90 percent of Ebola-infected mice for at least one month. Only 50 percent of the mice given Fareston survived for this length of time.

Mice that did not receive either treatment died in under 10 days.

Both drugs are known to target estrogen receptors, celluar proteins that interact with the sex hormone to mediate its physiological effects on the body. However, the researchers discovered that these receptors aren't needed for the Ebola to infect cells.

Recent studies have shown Ebola virus infects humans by catching a ride on a cellular shuttle — NPC1 — that is reserved for the essential nutrient cholesterol. Clomid appears to target this shuttle to prevent Ebola infection, according to the authors.

This project was a collaborative enterprise featuring scientists from the biopharma Zalicus, the University of Virginia, and the United States Army Medical Research Institute of Infectious Diseases (USAMRIID).

Because of the severity of Ebola hemorrhagic fever, government officials worry the virus could one day be weaponized into an agent of bioterror. Thus, development of therapy is not only a public health issue for Africa, where most Ebola outbreaks occur, but a potential concern for national security.

Source: Johansen LM, Brannan JM, Delos SE, et al. FDA-Approved Selective Estrogen Receptor Modulators Inhibit Ebola Virus Infection. Science Translational Medicine. 2013.