The drug Hydroxichloroquine is usually used to treat malaria, lupus and rheumatoid arthritis. But some studies are showing it could be effective at treating COVID-19, the disease caused by the coronavirus.

Will Humble, the former director of the Arizona Department of Health Services and division director for health policy and evaluation at the Center for Population Science & Discovery at the University of Arizona’s Health Sciences Center, says the drug is effective at keeping viruses from replicating and bolstering a patient's immune system.

"It interferes with its ability to replicate, but also, it may be acting in another way by modifying the body's immune response to the virus," he said.

The immune response to the virus is what causes much of the damage in COVID-19 patients, like lung inflammation.

Humble cited three studies conducted on lupus patients who recovered while taking the drug. Although the results of the studies were promising, he said it wasn't an instantaneous cure, and it could take time to get more of the drug on the market and determine the correct dosing for coronavirus patients.

"It’s a drug that already exists," he said. "There’s no additional FDA approval that’s needed. We know that it’s safe and we know there’s some preliminary data that suggests that it might very well be effective."

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Evidence, however, is lacking, according to Dr. Anthony Fauci, the director of the National Institute of Allergy and Infectious Diseases and member of the White House Coronavirus Task Force. While the drug is readily available, it hasn't been approved by the FDA to treat COVID-19, he said at a press briefing.

But researchers in France found the drug could clear upper airways of the virus in three to six days — much faster than the body's immune system, which takes about 20 days, effectively reducing the amount of time a person can transmit the disease. Research from China published in the journal Nature  found the drug inhibited viral growth in patients.

In the absence of a vaccine, Humble says the drug offers a glimmer of hope.

"This could actually be something that could be a real help to patients, and provide an opportunity to back off on some of the social distancing interventions that are very damaging to our economy," he said. "If I were a public figure with any responsibility, I would be moving very quickly to investigate these drugs and get them into wide circulation and use."