The first U.S. COVID-19 patient appeared at an urgent care in suburban Seattle with persistent cough and a fever on Jan. 19, four days after he returned from Wuhan, China.

The 35-year-old man had no prior health conditions, but he got sicker and sicker, according to the New England Journal of Medicine. After he was admitted to the hospital, he took a turn for the worse. His cough turned into pneumonia. By the tenth day of his illness, physicians put him on oxygen and administered an experimental antiviral drug called remdesivir.

A day later, the patient improved. Doctors removed the oxygen and his appetite returned. Other than a lingering cough, he appeared to have recovered.

The news, documented in a March 5 article published by the New England Journal of Medicine, buoyed hopes for a potential coronavirus treatment. Right now, there’s no approved treatment for COVID-19, the illness caused by a new coronavirus that has swept the globe since its emergence in late 2019, infecting more than 200,000 and killing almost 9,000.

Does the first U.S. case report prove remdesivir works?

“I don’t think so,” said Dr. Paul Goepfert, a researcher and physician at the University of Alabama at Birmingham. “It’s promising, sure, but there’s no way you can base anything on a single case.”

Remdesivir was developed through research centered at UAB’s Antiviral Drug Discovery and Development Center, in partnership with Gilead Sciences, a drug company. In the fight against COVID-19, it emerged as a leading contender.

It’s been highlighted at White House briefings earlier this week. President Trump described the treatment as “exciting." The U.S. Food and Drug Administration has pledged to help make the drug available quickly if it proves effective.

The compound’s turn in the spotlight didn’t come easily. Remdesivir has been around the block during previous pandemics, fizzling out in clinical trials or fading away when other outbreaks petered out.

The compound was originally developed as a broad-spectrum anti-viral with funding from the federal government. Introduced as a potential treatment for Ebola, researchers established its safety in early studies and rushed it into hard-hit areas of Africa during an outbreak that claimed more than 11,000 lives.

Although remdesivir showed promise in the lab, it proved less effective in clinical trials compared to other antiviral drugs. It was never developed as a treatment.

Still, the drug had shown promise against two other coronaviruses: SARS and MERS. Since both diseases had largely disappeared by 2019, so had research into the effectiveness of remdesivir. The emergence late last year of COVID-19, a new coronavirus, put remdesivir back on the fast track for study.

Labs at UAB and around the country have begun to ramp up production, racing to meet demand for clinical trials and requests for compassionate use. Patients critically ill with COVID-19 can request the drug directly from Gilead Sciences. At the same time, researchers are comparing the compound with placebos in trials all across the globe.

Early reports from 12 patients indicate the drug may have some side effects. Patients treated with the compound reported nausea and gastrointestinal discomfort, according to a paper published by analysts but not reviewed for scientific publication. The authors said the results couldn’t be evaluated for safety or effectiveness because they did not come from a clinical study.

The National Institutes of Health announced the launch of a remdesivir trial to treat COVID-19 on Feb. 25. Last week, three infected passengers from the Diamond Princess cruise ship had enrolled at the University of Nebraska Medical Center. Scientists in China have also established study sites there.

Although Goepfert at UAB said he won’t draw any conclusions from a single case, he said there are signs remdesivir might be effective this time around.

“It worked really well in the test tube,” Goepfert said.

It also looked good in animal models, the researcher added. Remdesivir works by tricking viruses and preventing them from replicating.

“Ideally, you’d hope that the virus would go completely away and the patient would get better,” Goepfert said.

Right now, many patients hospitalized with severe COVID-19 are requesting the drug for compassionate use, which is allowed for illnesses with no approved treatments. But Goepfert said early reports suggest the drug might be most effective when given early, before patients develop serious complications.

“Once you get to the point that you’re hospitalized, it’s very difficult to reverse that damage,” Goepfert said.

Goepfert said results of the first clinical trials are expected in April. Until then, researchers won’t know whether the drug really works and if it’s safe in patients suffering from COVID-19. UAB is one of the sites studying the drug.

A positive result would be great, but obstacles could slow the pipeline from labs to pharmacies. Dr. Francis Collins, who has frequently highlighted the potential of remdesivir, said the drug could be a “very appropriate way to try to treat people who have been infected.”

He also said Gilead might have to overcome production problems that emerged after COVID-19 crippled parts of China where pharmaceuticals are made.

“One of the things this shows is how vulnerable we are as a global community to pipeline disruptions,” Collins said. “It makes you realize you don’t have a good backup plan.”