Viruses are infectious particles that depend on host cells they infect to reproduce.
They consist of some genetic information, either DNA or RNA, encased in a protein shell called a capsid, which is sometimes enclosed by a lipid (fat) membrane.
Viruses can exist out in nature for some time, depending on the virus and the conditions.
To infect a cell, viruses use proteins on their surfaces to bind to proteins on the outside of a cell, and then they can send small capsids or their genetic information into the cell. Once they get into the cell, they hijack cellular functions to copy their genomes and make new proteins that are assembled into progeny viruses that can escape the cells by various means. Because viruses use our cells to replicate, it’s hard to design antivirals without too many side effects.
So how are antivirals designed? Scientists develop antivirals to minimize symptoms, reduce the replication of the virus and shorten the duration of the illness. Because viruses must replicate in cells, scientists study how each type of virus reproduces to find processes or proteins unique to the virus.
If they can find something that is essential for the virus to reproduce, they can create an antiviral that decreases the amount of virus so it does not cause disease.
Back in 1990, there were only five antiviral drugs, and today there are more than 100. Modern-day antiviral development is based on lessons learned in the development of drugs to treat HIV. Scientists determined how HIV reproduces, and the first unique protein activity they identified was a viral enzyme called reverse transcriptase (RT). RT copies the viral RNA genome into DNA that’s transported to the nucleus of an infected cell and integrates into the cellular genome. The first HIV drug targeted RT and was approved in 1987. There are now numerous other HIV antivirals that target different processes the virus needs to reproduce.
Scientists have a good understanding on the new coronavirus, SARS CoV-2, and have begun the development of new antivirals that specifically target viral processes.
We know that the viral receptor on the surface of human cells is one possible target. Viral entry into cells is facilitated by a protein, and we could stop that process. The virus also uses enzymes to copy its genome and process proteins. Just like with HIV, all of these are good drug targets.
In addition to developing new drugs, some existing drugs are being tested. Hydroxycholoroquine has been in the news, but it needs more testing to see if it helps with COVID-19 symptoms. Scientists think the drug may prevent the virus from getting into cells, and it also alters the immune response.
Remdesivir is promising because it could prevent the virus from replicating by blocking the enzyme that copies the viral genome. He can hope that a treatment will be available soon.
In the meantime, don’t take any medications without consulting with your physician. An elderly couple took chloroquine phosphate, used to treat aquarium fish; both were hospitalized, and the husband died.