A combination of three antiviral drugs plus an immune system booster seemed to help patients recover more quickly from coronavirus infections, doctors in Hong Kong reported Friday.

They said the approach needs more testing but it could offer another treatment possibility for Covid-19 patients. Currently the only authorized treatment is the experimental antiviral drug remdesivir, which also shortens the duration of illness but is limited in supply.

Dr. Kwok-Yung Yuen at Hong Kong University and colleagues tested the HIV drug combination of ritonavir and lopanivir along with the general antiviral drug ribavirin and a multiple sclerosis drug called beta interferon.

Patients in the study all had mild to moderate symptoms and were treated within seven days of testing positive. Some doctors think treating patients earlier in the course of the infection might be better.

Yuen's team gave some patients only the HIV drug combination, often sold under the brand name Kaletra. Other were randomly assigned to get the lopinavir-ritonavir combination plus the antiviral drug ribavirin and injections of beta interferon.

The patients who got the cocktail tested negative for coronavirus after seven days on average. Those who just got the HIV drugs were positive on average for 12 days, the team reported in the Lancet medical journal.

Few side effects, study says

The patients given the cocktail also felt better quicker -- within four days.

"Early triple antiviral therapy was safe and superior to lopinavir-ritonavir alone in alleviating symptoms and shortening the duration of viral shedding and hospital stay in patients with mild to moderate COVID-19," the researchers wrote.

There were few side effects, they added.

Dr. Peter Chin-Hong, who is treating coronavirus patients at the University of California San Francisco, said the study offers new hope in the pandemic.

"This study is really refreshing because it tells us remdesivir isn't the only game in town and maybe there are other options around," he told CNN.

"These drugs have a track record of safety," he said, adding they are also easily available.

Doctors and pharmacists have complained that they don't know which hospitals and clinics will get remdesivir, which was given US Food and Drug Administration emergency use authorization after it was shown to reduce the duration of illness in Covid-19 patients.

Chin-Hong said the Lancet study showed the possibility of other treatments.

"Maybe we can get this when we can't get the alleged magic bullet," he said.

Many groups are testing various combinations of drugs against coronavirus. Nothing is likely to be a cure, doctors agree.

"In Covid-19 we don't have the luxury of time," Chin-Hong said. "This is one of the treatment options where we are teaching old drugs new tricks. We don't have the time to take a drug rationally from beginning to end because we have a crisis right now. We have to make do with what we have."

CNN