After Germany’s CureVac, at least temporarily, dropped out of the race to make an mRNA-based vaccine in August, French drugmaker Sanofi has now abruptly done a volte-face, thereby generating about as much astonishment as any one company can within a few hours.

On the morning of Sept. 28, Sanofi reported encouraging results from Phase 1/2 trials with the mRNA-based Covid-19 vaccine candidate it was developing together with newly acquired subsidiary Translate Bio, waxing enthusiastic about the promise of its technology. On the afternoon of the same day, the Paris-based company announced it was dropping this vaccine from its program.

Instead, Sanofi said it will concentrate on the adjuvanted recombinant protein Covid-19 candidate it is developing in partnership with British drugmaker GlaxoSmithKline (GSK). Earlier this year, it had sidelined this project due to problems that delayed the progress of clinical trials. The change of strategy comes as new campaigns for booster shots are gearing up and it sees good chances to position its vaccine to supplement the first two doses of another.

Acting quickly after its advisory panel published its relevant guidance, the US Food and Drug Administration (FDA) last week in part recommended a booster dose to be administered at least six months after completion of the primary series. For now, this has been authorized solely for the Pfizer/BioNTech vaccine, the only one fully approved in the US.

Though for now the FDA’s green light currently applies to only this vaccine, it seems clear to most that boosters of more vaccines will be allowed, especially if other countries follow the lead of the US and the UK. Presently, only Americans over 65 years of age, immunocompromised or employed in high-risk jobs have access to the shot, but bets are on the eligible groups being extended as the campaign progresses.

In the UK, a booster dose is being recommended for the entire population.

Sanofi said it will file for approval of booster shots and two-shot primary vaccinations at the same time. Together the UK and the EU –  the latter has not yet authorized boosters –  have already ordered more than 75 million booster doses, it said. The drugmaker added that it will also supply the UN’s Covax program that distributes vaccines to developing countries. 

Praise for mRNA vaccine trial results

In a statement issued early in the day, Sanofi said the phase 1/2 trials with its mRNA vaccine confirmed the potential of the US biotech’s mRNA and lipid nanoparticle (LNP) platform and supported its own strategy. The good results also seemed to serve as  justification for pursuing the acquisition of the US biotech in the face of mooted opposition from the US Federal Trade Commission (FTC).

The Paris-based pharma said initial trial data with the mRNA candidate showed neutralizing antibody seroconversion (defined as 4-fold increase vs baseline) in 91-100% of study participants two weeks after a second injection, across all three dosages tested. No safety concerns were identified in the trials and the tolerability profile was shown to be comparable to that of other unmodified mRNA Covid-19 vaccines, it added.

Jean-Francois Toussaint, global head of research and development at Sanofi Pasteur, praised the trial results, which as he noted came just nine months after the worldwide proof of concept of mRNA vaccines and 17 months after the company’s own researchers started their first mRNA vaccine project. Calling the parameters “impressive,” he said this “will clearly help inform the path forward for our mRNA development programs.”

Clinical tests with mRNA-based flu vaccine in 2022?

Sanofi said also that it is moving toward using modified mRNA against other diseases, including influenza, and has targeted 2022 to begin clinical studies on a flu vaccine with modified mRNA. Phase 1 trials for this application are currently ongoing.

At the same time, the company noted that it was continuing its work on the vaccine being developed with GSK, with the help of funding awarded by the US Biomedical Advanced Research and Development Authority (BARDA) in early 2020. In parallel to its ongoing efficacy and safety study, it said it has expanded its program to include a study of the vaccine as a booster shot.

Recently published preclinical data for the adjuvanted vaccine showed that the candidate “has the potential to strongly boost immune responses following primary vaccination across multiple vaccine technology platforms and against a broad spectrum of variants of concern,” Sanofi said. First results of the booster studies begun during the summer months in the US, Australia, France and the UK are expected by the end of this year.

Author: Dede Williams, Freelance Journalist