DecryptionsAlong with Paxlovid, from Pfizer, authorized on January 21 by the HAS, several types of antivirals are being developed to treat symptomatic Covid-19. Here’s how they work.
Friday January 21, the High Authority for Health (HAS) gave the green light to the marketing of Paxlovid, from Pfizer, the first treatment against the coronavirus which should be available outside hospitals for people at risk suffering from Covid-19. 19 symptomatic.
This is a first in the history of the pandemic, since, since January 2020, the only known way to fight the disease is to treat the most serious symptoms in hospital: we try to regulate the the body’s immune response and to breathe oxygen into the lungs, which are attacked by both the virus and the inflammation. Until recent months, no drug had shown antiviral efficacy against the virus. This momentary failure hardly surprised the scientific community, which knows full well that it is much more difficult to target and fight a virus than a bacterium.
But in recent months, several antiviral molecules have shown clear activity against SARS-CoV-2, and raise real hopes of treating symptomatic cases of Covid-19 more easily and in greater numbers.
Here we have tried to explain how these drugs work inside cells.
Protease inhibitors
Example : Paxlovid, developed by Pfizer; pasitinib tested by AB Science. Novartis also says it is working on a protease inhibitor against all human coronaviruses.
It is a fairly well-known and long-used type of antiviral treatment. The principle is to prevent the virus from replicating, and therefore from infecting more cells. For this, the drug will target and neutralize a crucial viral protein for the coronavirus: its protease. Let’s see how it works in practice:
Mutagenic ribonucleotides
Example : Molnupiravir, developed by Ridgeback Therapeutics, with help from Merck.
This type of antiviral is a little more complex. Its strategy is similar to that of protease inhibitors, since it attacks the replication of the virus, but in a different way: instead of strictly preventing it, it inserts errors in the copy of the virus genome to make dysfunctional viruses, and therefore inoperative. Let’s see how it works:
Monoclonal antibodies
Example : Sotrovimab, developed by GSK; REGN-COV2, developed by Regeneron Pharmaceuticals and Roche; Bamlanivimab, developed by AbCellera Biologics and Eli Lilly.
Although not strictly speaking an antiviral, monoclonal antibodies can be effective against certain viruses. Used since the mid-1980s as anticancer drugs or against certain autoimmune diseases, these antibodies are produced in series in the laboratory using modified B lymphocytes and are called “monoclonal” because they only recognize a single antigen, a single target, which was previously chosen by the researchers. In this case, these monoclonal antibodies are designed to recognize the tip of the surface protein of SARS-CoV-2, the one that comes into contact with human cells to allow it to infect them. Demonstration:
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