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.

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.