A new study delves into how exactly an investigational antiviral drug, remdesivir, is being used as a treatment for COVID-19, the respiratory illness caused by a coronavirus similar to the Severe Acute Respiratory Syndrome (SARS) virus and the Middle East Respiratory Syndrome (MERS) virus. The study was led by a team of academic and industry researchers at the University of Alberta, Edmonton.

Viruses have molecular machinery that replicates their genetic material – coronaviruses do this by using an enzyme known as the RNA-dependent RNA polymerase. Until now, it has been difficult to get the polymerase complex to work in a test tube, but scientists under virologist Matthias Götte successfully modified polymerase enzymes from the coronavirus that causes MERS to test remdesivir.

They found that the enzymes incorporated remdesivir, which resembles an RNA building block, into new RNA strands and is soon unable to add more RNA subunits, effectively stopping genome replication.The scientists think that this might happen because RNA containing remdesivir takes on a strange shape that doesn’t fit into the enzyme.

Götte’s team previously showed that remdesivir could stop the replication of other viruses with RNA genomes, such as Ebola; but this new development would require additional data to help researchers design future drugs to have even greater activity against the coronavirus polymerase.