Paris (AFP)
The race for the Covid-19 vaccine is mobilizing large pharmaceutical companies and grabbing media attention. A more discreet competition is playing out between laboratories to quickly find monoclonal antibodies capable of neutralizing the new coronavirus.
These modern therapeutic tools, used for around thirty years to treat cancers or inflammatory diseases, would be the weapons of choice in the arsenal being built up against SARS-CoV-2.
Originally, monoclonal antibodies are molecules naturally produced by our immune system to trigger a targeted attack when faced with a danger: cancer cells, bacteria or viruses. To be able to use them for therapeutic purposes, laboratory techniques make it possible to clone them.
Dozens of research teams around the world are currently working to quickly select antibodies capable of effectively neutralizing the coronavirus responsible for a pandemic that has killed more than 320,000 people worldwide.
Such antibodies are selected from the blood of cured patients or produced in the laboratory from specially developed cell lines.
They have in common to attack the protein S by which the SARS-CoV-2 virus binds to the surface of human cells and which plays a key role in the infectious process, explains to AFP the researcher Hugo Musket.
- "Promise of an effective antidote" -
His Paris laboratory of humoral immunology at the Institut Pasteur embarked on this race for antibodies two months ago. He has already made a first selection of antibodies from the blood of ten French patients who have presented a "strong immune response".
Other laboratories are more advanced and publications on the discovery of anti-coronavirus antibodies follow one another at a sustained pace, with a total of fifteen articles on the subject, according to Hugo Mouquet.
On Monday, a Swiss-American team announced in the journal Nature the discovery of a "promising" neutralizing "human monoclonal antibody". This antibody, called S309, "contains the promise of an effective antidote to limit the Covid-19 pandemic", according to the researchers.
It has the particularity of having a broad spectrum neutralizing activity against sarbecoviruses, a category of coronaviruses of which SARS-CoV-2 and the virus responsible for the SARS epidemic in 2003 belong.
A few hours earlier, a Chinese team announced in the American journal Cell that they had also discovered effective neutralizing antibodies.
A cocktail of 14 antibodies, selected from the blood of 60 convalescent Chinese patients, has been successfully tested in mice, allowing sick animals to heal and healthy animals to remain protected after contamination in the laboratory.
Clinical trials on humans with this cocktail are in preparation and a treatment could be available before the end of the year, Sunney Xie, principal author of this research and director of the Center for Advanced Innovation, told AFP. genomics of Peking university.
- Beneficial ricochet effect -
This type of delay is "entirely possible", according to Hugo Mouquet. It takes, indeed, approximately six months to carry out tests of effectiveness of monoclonal antibodies on the man.
Even if they can a priori be used as a vaccine to prevent infection, the monoclonal antibodies "would have more a therapeutic virtue than a preventive" in the case of the Covid-19 disease, underlines the French researcher.
They will not be competitors but complementary to vaccines, he anticipates.
Indeed, precise knowledge of the modes of action of monoclonal antibodies on the coronavirus will in turn have a beneficial effect on vaccines. Such knowledge will allow the development of "more precise and effective vaccines" compared to those of the first generation which are currently being developed, still believes the researcher.
There remains a major obstacle: their cost, so far high. For example, one of the oldest and most sold monoclonal antibodies in the world, infliximab, which notably treats Crohn's disease and rheumatoid arthritis, costs in France around 500 euros per infusion.
© 2020 AFP