Promising results have been reported from a clinical trial of an experimental antiviral drug called remdesivir - but how does it work and what does this mean for the treatment of COVID-19?
Many COVID-19 researchers are focused on the search for drugs to treat the disease. Antiviral drugs are a type of medication used to treat viral infections by interfering with part of the virus lifecycle, such as entry into human cells or viral replication. These drugs aim to reduce symptoms or lower the rate of serious complications or death caused by the virus. Most current antiviral drugs do not completely cure the diseases they treat, but can be useful tools in managing them.
Preliminary results have been reported for the largest trial yet of remdesivir, a candidate antiviral drug for COVID-19 produced by the pharmaceutical company Gilead Sciences. Remdesivir works by interfering with the copying machinery that SARS-CoV-2, the virus that causes COVID-19, uses to replicate its genetic material when the virus grows in our cells. Earlier this year, researchers showed that the drug reduces viral replication in cultured human cells infected with SARS-CoV-21.
In the recent trial, 1063 hospitalised patients with severe COVID-19 were given either remdesivir or a placebo, and their symptoms were monitored. Early results from the trial suggests that patients given remdesivir recovered 31% faster than those given the placebo, with the average recovery time falling from 15 to 11 days2. Although this result is preliminary, the study showed strong support for this acceleration of recovery. The results also suggest a possible survival benefit, with a mortality rate of 8.0% in the remdesivir-treated patients compared to 11.6% in the placebo group, although the difference was not statistically significant.
The full results from the trial are yet to be released, meaning that the scientific community has not yet been able to examine the results in detail to confirm that they are robust. However, based on these promising preliminary data, the United States Food and Drug Administration (FDA) has granted the drug an “Emergency Use Authorization” for use in patients with severe COVID-19. This early-approval mechanism was previously used in the HIV pandemic to provide drugs to terminally ill patients, even if those drugs had not passed the usual standards of safety and efficacy yet.
But not all trials are giving remdesivir the thumbs up. Some earlier studies have shown conflicting results, for instance a smaller study from China found no benefit to recovery time3. Results from the treatment of more patients will be needed to understand fully how, if at all, remdesivir can affects the course of COVID-19.
Remdesivir is given by injection. Documented side effects include anaemia and organ impairment, so this drug is unlikely to be suitable for use in mild COVID-19 cases or as a preventative treatment. It is also not yet licensed in the UK and further clinical trials are underway to test its safety and efficacy. Unfortunately, some of these trials have been overshadowed by doubts about the supply of the drug. Professor Mahesh Parmar, director of the clinical trials unit which ran the UK arm of the Gilead trial, said at a recent briefing, “it is very difficult to obtain the drug. The trial did give us access to remdesivir [but] I think supply is going to be a real problem.”
The important message from these early results is that remdesivir seems to reduce the length of COVID-19 illness, although further research is needed to confirm this. And it remains to be seen if it could help to reduce mortality rates. That said, a shorter disease course alone could help to free up hospital beds for other patients, taking pressure off the stretched healthcare system and reducing the so-called “secondary” or indirect “knock-on” deaths. Work on this antiviral drug and many other candidates continues as scientists hope to find safe and effective treatments to improve outcomes for COVID-19 patients.
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