The vaccine candidate from Sanofi and GSK will continue its development, after the success of the phase 2 trial carried out in recent months by the two laboratories. The serum produced a “high concentration of neutralizing antibodies in adults, all age groups combined”, welcomed Sanofi on Monday, even if this concentration remains higher in young people. The French group also indicated that the phase 3 trial would start “in a few weeks”.
In detail, the results announced show “seroconversion in 95 to 100% of cases after the administration of a second dose,” said a press release. Other good news: the vaccine candidate has generated a strong immune response in people who have already been infected with Covid-19, “which underlines the strong potential interest represented by its development for booster vaccination”.
Approval expected in Q4
The phase 3 study foresees the recruitment of more than 35,000 participants in several countries. It will have to confirm the hopes born in phase 2, but also to test the candidate vaccine against the variants. At the same time, studies will be carried out to determine whether this vaccine can be used for a booster, whatever the vaccine initially received.
Announced in April 2020, the partnership between Sanofi and GSK initially aimed for production in the second quarter of 2021. But in December, the results of the phase 1/2 study had shown insufficient efficacy in older people, forcing the laboratory to review its copy. With the success of phase 2 announced on Monday, and subject to positive results from phase 3, the vaccine “should be approved in the fourth quarter of 2021,” says Sanofi.
Not the same technology as Pfizer or Moderna
The technology used by the French laboratory is the same as for its seasonal flu vaccine. It replicates the genetic code of proteins on the surface of the virus – in this case the Spike protein, which allows the coronavirus to enter human cells. Purified, this protein can trigger the production of antibodies by simulating an infection without making the person sick.
For its vaccine against Covid-19, Sanofi has chosen to combine it with an adjuvant. This – produced by GSK – makes it possible to limit the number of proteins required per dose of vaccine, by boosting the immune response, and therefore significantly increasing production capacity.
This recombinant protein technology is different from messenger RNA, the one used by Pfizer-BioNTech and Moderna for their anti-Covid vaccines. The latter aims to make the human body manufacture the Spike protein directly, by giving “instructions” to the cells. Once produced, the protein is memorized by the immune system, which will be able to fight it off if the virus enters the body.
In partnership with the American biotech Translate Bio, Sanofi has also launched a clinical trial of a vaccine candidate using messenger RNA technology. The interim results of phase 1/2 are expected in the third quarter of 2021.
More than 700 volunteers recruited for phase 2
Randomized, double-blind, the phase 2 study was conducted in adults aged 18 and over “with the aim of evaluating the tolerance, reactogenicity and immunogenicity of two injections administered 21 days apart” , says Sanofi. An equivalent number of adults aged 18 to 59 and adults over 60 were included in the study. The 720 volunteers were recruited from the United States and Honduras.
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