Researchers and physicians at the University of Washington in Seattle are treating patients diagnosed with COVID-19 using a drug best known as a therapy for malaria, part of a broader global effort to evaluate existing medications and treatments in the battle against the disease.

The drug, hydroxychloroquine, is “very promising” as a treatment for COVID-19, said Rodney JY Ho, a professor and presidential entrepreneurial fellow at the UW who is working closely with researchers at the university who are focusing on the novel coronavirus and its effects.

However, he and other researchers caution that it has not gone through clinical trials in the U.S. with people who have been infected with COVID-19, and there’s not enough data to reach definitive conclusions about its effectiveness in treating the disease.

“There are certain stages of this disease when the drug may be helpful,” Ho told GeekWire.

Hydroxychloroquine is not new to the market. It was first introduced to treat and prevent malaria, lupus, arthritis, and now, maybe, coronavirus. Lab studies indicate that the drugs may keep coronavirus from invading human cells after anecdotal reports in China and France hinted at recoveries.

The idea is to “slow down the virus” and prevent health care providers and others from being exposed, Ho said. However, he made it clear that hydroxychloroquin is not a “cure” for the disease. That would require prevention and early detection of people exposed to the novel coronavirus.

UW assistant professor and physician Arun Sidhar said on Twitter this week that the University of Washington plans to use hydroxychloroquin “for all patients warranting hospital admission” who have been diagnosed with COVID-19. He also offered guidance for monitoring the electrocardiogram results of patients treated with the drug to avoid side effects.

UW Covid team is going to use Hydroxychloroquin for all patients warranting hospital admission. We came up with this quick and simple guideline for QTc cutoffs during treatment. Feel free to adapt and use if your hospital is using hydroxychloroquin for these pts. #COVID19 pic.twitter.com/c8ggkR531A — Arun Sridhar (@ArunRSridhar) March 17, 2020

President Donald Trump and other federal officials addressed the potential for hydroxychloroquin to treat COVID-19 during a briefing with reporters on Thursday, bringing new attention to the concept of using existing therapies to treat COVID-19 or slow the spread of the disease.

“In the short term we’re looking at drugs that are already approved for other indications,” FDA Commissioner Stephen Hahn said during the White House briefing. However, he said, the ideal approach is “to do that in the setting of a clinical trial — a large, pragmatic clinical trial to actually gather that information and answer the question that needs to be asked and answered.”

Hydroxychloroquine is one of nearly a dozen drugs being used in clinical trials in China to address the COVID-19 outbreak. One drug being tested in the U.S. is remdesivir, an antiviral therapy that was used in trials for Ebola and the coronavirus MERS. Pharmaceutical company Gilead Sciences developed remdesivir initially to treat Ebola.

The New York Times reported in early February that doctors in the Seattle region used remdesivir to treat the first patient diagnosed with COVID-19 in Washington state, and saw a noticeable improvement in his symptoms the following day.