Remdesivir: is the antiviral drug a cure for coronavirus?

A US trial of Covid-19 patients found the drug cut recovery time by four days on average, but many questions remain and larger studies are needed

Gilead Science's remdesivir, one of the most highly anticipated drugs being tested against the new coronavirus, showed positive results in a US government trial. AFP

The US government has said it was working to make the antiviral medication remdesivir available to patients as quickly as possible after a major study found it could shorten the time it takes for Covid-19 patients to recover by an average of four days.

However, the study is yet inconclusive and far more needs to be learned before health officials begin using the drug. Here's everything you need to know:

It was developed to treat Ebola

Remdesivir is an experimental antiviral produced initially as a potential treatment for the Ebola virus by the US pharmaceutical company Gilead. However, in 2019 Congolese health officials said the drug was less effective than other treatments.

It has showed promising results in preventing Middle East Respiratory Syndrome (Mers-CoV) and severe acute respiratory syndrome (Sars), which are also caused by coronaviruses. But those studies have only been done in animals. Remdesivir also showed promise in rhesus macaque monkeys infected with the new coronavirus, according to a small, seven-day study of six monkeys that has yet to be published in a peer-reviewed journal.

How does it work?

In Mers-CoV studies, US researchers found remdesivir blocks a particular enzyme that is required for viral replication.

The drug was administered during the trial via daily infusion for about 10 days and appeared to reduce fever and alleviate respiratory symptoms associated with coronavirus, allowing many patients who receive it to be discharged from the hospital in less than a week.

However, it has not been yet been approved by health authorities around the world, and supply is low. But it is being used in clinical trials, and many countries are attempting to get access to the drug for use in their own Covid-19 studies.

A Buddhist monk scatters seeds on a rice paddy to mark the start of the cultivating season in Piliyandala a suburb of the Sri Lanka's capital Colombo. The usually grand ceremonies were scaled down as the country remained under a curfew to prevent the spread of the novel coronavirus which has infected 650 people and claimed seven lives. AFP

Homeless women wear protective face masks as they wait for free food near a market area during a lockdown in place to prevent the spread of coronavirus in Kolkata, India. According to media reports, Prime Minister Modi announced that India's initial 21-day lockdown will be extended until 03 May 2020 in an attempt to curb the spread of coronavirus. EPA

Nurse Shirley Molloy tests a patient for COVID-19 at a drive-through Fever Clinic in Caloundra on the Sunshine Coast, Australia. The Queensland Government has announced that some restrictions will be eased starting 02 May 2020 due to a very low number of new COVID-19 infections. EPA

Buddhists wearing protective masks attend a service at Joggye Temple in central Seoul , South Korea, as they take part in a prayer service for the ongoing fight against the coronavirus and to celebrate Buddha's birthday. EPA

A Peruvian is seen looking outside of a tent while living on the street waiting to be tested for the coronavirus disease (COVID-19) and allowed to return home to another part of the country, in Lima, Peru. REUTERS

A swab chamber used by health workers to perform coronavirus disease (COVID-19) nasal swab tests is seen in Depok, during the outbreak of coronavirus disease (COVID-19) in Jakarta, Indonesia. REUTERS

A health worker takes a rest during a nasal swab test for coronavirus disease (COVID-19) in Jakarta, Indonesia. REUTERS

A handout photo made available by the Executive Committee for Changi Exhibition Centre Facility shows COVID-19 patients alighting a van before entering a community isolation facility at the Changi Exhibition Centre in Singapore. Singapore has seen a surge in the number of cases, with a majority of patients being work pass holders staying in foreign worker dormitories. To cope with the surge, Singapore has set up community isolation facilities with a capacity of over 41,000 beds. EPA

People ride bicycle in New York's Times Square, Wednesday night, during the coronavirus pandemic. President Donald Trump said Wednesday the federal government will not be extending its coronavirus social distancing guidelines once they expire Thursday. AP

An employee working at a textile factory in Handan in China's northern Hebei province. Chinese factory activity continued to expand in April, data showed on April 30, but analysts warned that the outlook remained clouded by battered overseas demand as the rest of the world struggles to overcome the coronavirus pandemic. AFP

Buddhist believers wear masks as a preventive measure against the coronavirus (COVID-19), as they gather during a birthday of Buddha and service to pray for overcoming the coronavirus (COVID-19) pandemic at Jogyesa Temple in Seoul, South Korea. Buddha was born approximately 2,564 years ago, and although the exact date is unknown. South Korea reported yet another single-digit increase in the number of coronavirus infections, but the country is keeping a watchful eye on this week's holidays, which could lead to more cases. According to the Korea Center for Disease Control and Prevention, 4 new cases were reported. The total number of infections in the nation tallies at 10,765. Getty

Some of the spilled masks are visible on the shoulder of southbound Interstate 880 in Union City, Calif. In the midst of the coronavirus pandemic, the freeway suffered a mini-traffic jam when someone tossed hundreds of face masks onto the road and some motorists stopped to grab them, the California Highway Patrol reported. At around 1:30 p.m., CHP officers received a report that a white truck had stopped on Interstate 880 in Union City and someone tossed out boxes of medical masks, the CHP reported. AP

Nurses with goggle marks and plasters on their faces walk after their shift at the intensive care unit where patients with COVID-19 are treated at Juarez hospital, as the coronavirus disease (COVID 19) continues in Mexico City, Mexico. REUTERS

Sandra Perez, left, purchases goods at a grocery store she intends to donate to needy families, in the Harlem neighborhood of New York. AP

People wear face masks as a mandatory precaution for riding on public transportations amid the coronavirus disease (COVID-19) outbreak while walking on the platform of a metro station in Taipei, Taiwan. REUTERS

A soldier stands at a checkpoint during a joint operation by police and army, as part of security measures to keep people out of the city downtown during a quarantine throughout the country to curb the spread of the coronavirus disease (COVID-19), in San Salvador, El Salvador. REUTERS

What do the studies show?

The US government’s top infectious disease expert Dr Anthony Fauci said data from one clinical trial “shows that remdesivir has a clear-cut, significant, positive effect in diminishing the time to recovery”.

The trial of more than 1,000 patients at University of Chicago Medicine showed those given remdesivir improved after an average of 11 days, compared with an average of 15 days for those not given the treatment. There was no statistically significant improvement in survival rate between the two groups.

However, the results were one part of a Phase 3 clinical trial for the drug, when doctors test a few hundred patients looking for efficacy and adverse effects. The next and last phase involves testing the drug in a much larger group of patients. There was also no control group, meaning scientists can't compare these patients with a group of equally sick individuals who did not receive the drug.

Similar clinical trials for severe and moderate Covid-19 cases are being run at institutions all over the world, but those results aren't yet public.

A smaller study of 200 patients in Wuhan, China, where the virus is thought to have originated, showed no statistically clinical benefit in Covid-19 patients in health improvement or mortality. However, the researchers said a larger trial was needed.

The conclusion 

It is not yet clear if remdesivir's efficacy is affected by factors such as the patient's age, the stage of the disease they are at or other factors. It is also not yet obvious who is benefiting from remdesivir or whether the patients who recovered would have recovered anyway. It is hoped that wider studies will answer many questions scientists have about the drug, but medical responses should not be based on the outcome of one trial.