By Maggie Fox

They were delighted to find a drug already on the market and considered safe to use in pregnant women. “Niclosamide is an FDA-approved drug (trade name Niclocide) that has been used in humans to treat worm infections for nearly 50 years, and it is well tolerated,” the team wrote in their report, published in the journal Nature Medicine.

“It is known to inhibit several viruses in culture systems, including the Japanese encephalitis flavivirus.”

Japanese encephalitis is a relative of Zika and also carried by mosquitoes.

Tests on human brain stem cells in lab dishes showed it could interfere with Zika’s replication in those cells. “Niclosamide is a category B drug, which indicates that no risk to fetuses has been found in animal studies. It has low toxicity in mammals,” they added.

“EMRICASAN WAS WELL TOLERATED IN HUMAN TRIALS, AND THERE WERE NO SIGNIFICANT ADVERSE EVENTS.”

Another drug, called emricasan, helped prevent Zika from killing those cells.

“Emricasan is currently being evaluated in phase 2 clinical trials for the reduction of hepatic injury and liver fibrosis caused by chronic hepatitis C infection,” the team wrote.

Emricasan was well tolerated in human trials, and there were no significant adverse events.”

A third compound called PHA-690509 also helped stop Zika replicating and from killing nerve cells, they said.

While the drugs work well in lab dishes full of cells, “we don’t know if they can work in humans in the same way,” Song said.

Niclosamide works in the gut, but it’s not clear if it’s possible to get it into the brain, Song said.

The researchers think the drugs might work best as a cocktail, attacking the virus from several fronts — in much the same way as drug cocktails fight the human immunodeficiency virus (HIV) that causes AIDS.