New York (CNN Business) Shares of American biotech firm Gilead Sciences rose nearly 5% Monday after an official from the World Health Organization said that Gilead's drug remdesivir is showing signs that it may be able to help treat the deadly coronavirus.

"There is only one drug right now that we think may have real efficacy and that's remdesivir," Bruce Aylward, an assistant director-general of the World Health Organization (WHO), said at a press conference in Beijing.

WHO officials added that clinical trials for remdesivir in humans are now taking place and results could be available within weeks.

Gilead Sciences confirmed in an e-mail to CNN Business that that it is working with health authorities in China on two trials for patients who have been infected with Covid-19, the official name of this particular strain of coronavirus.