While many scientists are working on developing a coronavirus vaccine, others are busy testing antiviral drugs.
Vaccines are generally only effective when administered prior to infection, but antiviral agents are important because they can treat people who already have COVID-19.
Here’s an overview of antiviral drugs scientists are investigating for coronavirus.
Targeting the copy cats
How do antiviral drugs work? First, it’s important to understand the genome of animals and plants is composed of deoxyribonucleic acid (DNA), but viral genomes can also be comprised of ribonucleic acid (RNA). This is the case for SARS-CoV-2 coronavirus – the virus that causes COVID-19.
In order to replicate, an RNA virus needs to make more copies of its RNA genome. This means antiviral drugs that block the copying of RNA genomes can potentially help treat COVID-19 patients. These drugs are known as RNA-polymerase inhibitors.
These types of drugs have successfully cured people of chronic hepatitis C – another RNA virus infection.
But not all viral RNA polymerases are the same, so the drugs that work for hepatitis C virus will not necessarily work for human coronaviruses.
Favilavir is an RNA polymerase inhibitor drug scientists are currently trialling against coronavirus.
Stopping the virus in its tracks
Another successful antiviral drug strategy is to use non-functional “analogues”, or inauthentic copies of the basic building blocks of the viral RNA genome. The presence of these analogues in the viral genome blocks the viral polymerase, meaning the virus cannot make another copy of its RNA. Acyclovir, ribavirin and azidothymidine (AZT) are examples of these drugs.
Unfortunately, this coronavirus is a bit tricky, because it “proofreads” the authenticity of its RNA genome. As such, it identifies the analogues as being inauthentic and removes them. This stops certain antiviral drugs like ribavirin from being effective.
Fortunately, the coronavirus’ proofreading powers don’t block a similar drug, remdesivir. So remdesivir potently halts coronavirus replication and represents a promising drug option for COVID-19 patients.
Remdesivir is also effective against other RNA viruses including the Ebola virus and the coronaviruses SARS and Middle Eastern respiratory syndrome.
Scientists are currently assessing remdesivir in clinical trials in the United States and China. Time will tell if remdesivir is effective for COVID-19 patients. But doctors are already considering how the drug is best administered for optimal results and whether it should be used in combination with other drugs or as a single agent.
Other proven antiviral drugs
Many RNA viruses produce a single “multi-protein” that’s later broken down into individual proteins via enzymes called “proteases”. Any molecules that inhibit these proteases have the potential as antiviral drugs. Viral protease inhibitor drugs have been highly effective in treating the human immunodeficiency virus (HIV) and hepatitis C virus.
Lopinavir and ritonavir are a combination of protease-inhibitor drugs (Kaletra) that can inhibit coronaviruses in human cells. Kaletra has already been used to treat a patient with COVID-19 in South Korea, but a larger trial found its effects were unconvincing. The reasons for these discrepancies are currently unclear and more research is obviously needed.
With any antiviral drug, the sooner it’s administered once a patient is infected, the better the outcome. This is because viruses replicate quickly, producing tens to hundreds of new infectious viruses.
Lisa Sedger (March 30, 2020). In the fight against coronavirus, antivirals are as important as a vaccine. Here’s where the science is up to [Blog post]. Retrieved from https://buff.ly/341vYm7
