Sanofi Ends a Covid-19 Vaccine Effort

Sanofi SA SNY 0.38% won’t proceed with the development of one of its experimental Covid-19 vaccines, saying it didn’t make sense to go forward in an already-crowded market.

The decision comes despite promising early results for the shot. The French healthcare giant said Tuesday that the vaccine—a so-called mRNA shot that uses the same technology as shots developed by Pfizer Inc. and Moderna Inc. —produced neutralizing antibodies against the virus in early-stage clinical trials. But it said it had decided not to proceed with larger studies, called Phase 3 trials, which would be required to win regulatory approval.

Thomas Triomphe, head of Sanofi’s vaccine business, said it didn’t make sense to pursue the mRNA vaccine when the market was already well served. Instead, Sanofi will pivot its mRNA research efforts toward other infectious diseases. It is already conducting early-stage clinical trials on an experimental mRNA shot against flu.

“The needs of the 2020 pandemic are completely different from the needs of the 2021 pandemic,” Mr. Triomphe said in an interview. “Is my best use of resources to start a Phase 3 program and get results, register it and then get an mRNA Covid-19 vaccine available in August 2023?”

Sanofi is also developing a more traditional vaccine against Covid-19 in partnership with GlaxoSmithKline PLC. Mr. Triomphe said the case to continue work on that vaccine is stronger because it is at a more advanced stage—results from its late-stage trial are expected later this year—and could be useful as a booster shot.

Sanofi lagged behind rivals such as Pfizer and partner BioNTech SE, and Moderna, which quickly developed mRNA vaccines against Covid-19 and won emergency authorization from regulators around the world last winter.

AstraZeneca PLC and Oxford University used a more traditional vaccine approach with their own two-dose vaccine. That also won emergency-use authorization in many places. All three groups of shot makers have sharply ramped up production. China and Russia have also developed and deployed homegrown vaccines.

Sanofi has long viewed mRNA as a promising technology. It first tiptoed into mRNA vaccine research in 2018 when it struck up a collaboration with Translate Bio to investigate the potential of the technology against a range of infectious diseases. Its Covid-19 shot was also the result of a collaboration with Translate Bio, which it has since acquired for $3.2 billion.

Mr. Triomphe hopes that Sanofi will be able to develop mRNA vaccines that can be stored at refrigerator temperature rather than the ultracold conditions that they currently require.

Write to Denise Roland at

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