Sanofi and Translate Bio initiate Phase 1/2 clinical trial of mRNA COVID-19 vaccine candidate

• Clinical trial to assess safety, immune response and reactogenicity, after preclinical data showed high neutralizing antibody levels
• Expected to enroll 415 participants; interim results expected in Q3 2021
• In parallel, preclinical studies are underway to evaluate additional mRNA candidates against emerging SARS-CoV-2 variants

PARIS and LEXINGTON, MASS. – March 12, 2021 - Sanofi Pasteur, the vaccines global business unit of Sanofi, and Translate Bio (NASDAQ: TBIO), a clinical-stage messenger RNA (mRNA) therapeutics company, today announced the start of the Phase 1/2 clinical trial for MRT5500, an mRNA vaccine candidate against SARS-CoV-2, the virus that causes COVID-19. The Companies expect interim results from this trial in the third quarter of 2021.

“Our mRNA vaccine candidate is the result of our expertise in infectious diseases coupled with the innovative technologies of our partner,” said Thomas Triomphe, Executive Vice President and Global Head of Sanofi Pasteur. “Initiating the Phase 1/2 trial represents an important step forward in our goal of bringing another effective vaccine to the ongoing fight against the COVID-19 pandemic.”

“We have made important progress towards developing mRNA vaccine candidates for infectious diseases through our collaboration with our partner Sanofi Pasteur,” said Ronald Renaud, Chief Executive Officer of Translate Bio. “With the impact of mRNA vaccines demonstrated during the pandemic, our joint development team remains steadfast in our commitment to advancing MRT5500 as part of the collaborative effort to overcome this global health crisis.”

Preclinical studies are ongoing and will continue over the next several months to evaluate whether MRT5500, as well as additional mRNA vaccine candidates, will induce neutralizing antibodies against the emerging SARS-CoV-2 variants, with the potential to inform current and future clinical development.

The joint development team is working on improving the temperature stability of the mRNA vaccine candidate and targeting a -20°C storage temperature for late-stage clinical trials and at launch. Efforts are also underway to enable the product to be stable at routine refrigerator temperature (2-8°C).

MRT5500 is being developed under a collaboration and license agreement between Sanofi Pasteur and Translate Bio.