Behind Sanofi’s mRNA Vaccine Candidate

Since 2018, Sanofi scientists have been working with Translate Bio, a clinical-stage biotechnology company that specializes in mRNA therapies, to design and develop a messenger RNA (mRNA) technology platform for vaccines. The platform will help researchers target an array of pathogens, including SARS-CoV-2, the virus which causes COVID-19.

Su Peing Ng

"We combine maths and molecules so we can fully exploit all the digital tools and data at our disposal. That’s essential for putting mRNA vaccines candidates on a successful path, not just for COVID-19, but for the many infectious diseases–including seasonal influenza–that routinely threaten public health."

Sabine Vital, Head of Scientific and Digital Innovation, Vaccines R&D at Sanofi

Sudha Chivukula

“This is a real paradigm shift in how we think about vaccines—one that gives us more ways to design, develop, manufacture, and deliver vaccine candidates.”

Sudha Chivukula, Head of the Vaccines mRNA Center at Sanofi

mRNA vaccine

Vaccines work by teaching the body to recognize and destroy pathogens–germs such as viruses and bacteria. That learning process can begin with a small piece of the pathogen; often one of its proteins (referred to as an “antigen”).

For its SARS-CoV-2 vaccines, Sanofi scientists are teaching the body to recognize and target an antigen known as the spike protein, which sits on the surface of the coronavirus. The spike protein helps the virus get into a person's cells, including those in the lungs.

Spike proteins on the surface of a SARS-CoV-2 virus. Vaccines help the body (1) recognize these signature proteins and (2) train the immune system to mount an attack when a whole virus invades

The core substance of a vaccine–the antigen–is often made as a purified protein in the lab, then formulated with other ingredients that help prompt the immune system to respond. But the antigen can also be generated directly in the body using the cell's own biological machinery: mRNA.

mRNA is a dynamic piece of genetic material that supplies the tiny biological factories inside cells with instructions for making proteins. An mRNA vaccine is designed to prompt the body's cells to make enough antigen—in the case of SARS-CoV-2, the spike protein—to stimulate the immune system to launch a fleet of protective antibodies.

Delivery in a nanoparticle

mRNA is active, fragile, and easily broken down. It must be packaged carefully to ensure that it can get to the right place in the body: inside cells, where the protein-making machinery resides.

Sanofi scientists package mRNA in lipid nanoparticles (LNPs): tiny, spherical droplets made of specialized fats called lipids. In the body, these droplets are engulfed by cells and, once inside, release their contents.

Discover how an mRNA vaccine is designed to work

Lipid nanoparticles have emerged as safe and effective delivery vehicles, particularly for RNA-based therapeutics. Engineering these nanoparticles—and their precious mRNA cargo—requires deep expertise in computer-based approaches, including machine learning and computational structural biology.

"Working with Sanofi to deliver vaccines on a global scale is enabling us to address a serious public health need with COVID-19. Looking beyond the current health crisis, we are expanding our mRNA technology platform by advancing vaccines against a broad range of infectious diseases toward clinical development."

Ronald Renaud, Chief Executive Officer of Translate Bio

Find out more

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  • Li F (2016) Structure, Function, and Evolution of Coronavirus Spike Proteins. Annu Rev Virol 3:237-261. doi: 10.1146/annurev-virology-110615-042301
  • Rodríguez-Gascón A, del Pozo-Rodríguez A, Solinís MÁ (2014) Development of nucleic acid vaccines: use of self-amplifying RNA in lipid nanoparticles. Int J Nanomed 9:1833-1843. DOI: 10.2147/ijn.s39810