PARIS and LEXINGTON, MASS. ? October 15, 2020?- 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 preclinical results for MRT5500, a mRNA-based vaccine candidate against SARS-CoV-2, the virus that causes COVID-19 disease.

Preclinical evaluation of MRT5500, importantly, demonstrated a favorable immune response profile against SARS-CoV-2. These data support the selection of MRT5500 for clinical development. A Phase 1/2 clinical trial is anticipated to begin in the fourth quarter of 2020. Full results are available?here. MRT5500 is being developed under a collaboration agreement between Sanofi Pasteur and Translate Bio.

?To tackle this global pandemic, we must look to both the strong knowledge we have from years of infectious disease expertise and the promise of new, innovative technologies,??said Thomas Triomphe, Executive Vice President and Global Head of Sanofi Pasteur.??Today?s presentation of these positive results is another development milestone for providing a safe and effective potential vaccine against SARS-CoV2 and shows how promising this technology is. We are looking forward to working on next steps with our partner Translate Bio to bring this technology to people worldwide.?

?The rapid development of effective vaccines to address the COVID-19 pandemic continues to be an urgent global public health need and?I am encouraged by the progress we?ve made to date with our partner Sanofi Pasteur toward the development of a promising mRNA vaccine candidate,??said Ronald Renaud, Chief Executive Officer at Translate Bio.??The preclinical results we report in this paper demonstrate the ability of MRT5500 to elicit a favorable immune response in both mice and non-human primates. Importantly, these results provide additional support for using our mRNA platform to potentially expedite the development of alternative approaches to traditional vaccines.?

Key preclinical findings The main findings of the preclinical studies demonstrate the potential of MRT5500 to elicit neutralizing antibodies against SARS-CoV-2.

In mice, four dose levels were assessed at 0.2, 1, 5 and 10 ?g per dose using a two-dose vaccination schedule, administered three weeks apart. MRT5500 induced dose-dependent levels of binding antibodies and neutralizing antibodies specific to the SARS-CoV-2 spike protein. 100% seroconversion was observed at all dose levels after one administration, and a further increase in titers was observed following a second administration. Neutralizing antibody titers were observed across all dose levels after receiving the two-dose-administration regimen. In the higher dose groups (5 ?g, 10 ?g), titers were detected after one administration of MRT5500 and were more pronounced after the second administration.

In non-human primates (NHPs), three dose levels were assessed at 15, 45 and 135 ?g per dose using a two-administration vaccination schedule, three weeks apart. The potency of MRT5500 was assessed by two types of neutralization assays: pseudovirus neutralization and micro-neutralization. After the first administration, the majority of NHPs developed neutralizing antibodies reactive to the SARS-CoV-2 spike protein and those antibody titers were further enhanced after a second administration with 100% of NHPs reaching levels significantly higher than those from human convalescent sera by day 35.

It was also demonstrated that MRT5500-immunized mice and non-human primates exhibited a Th1-biased T cell response against SARS-CoV-2.

The preprint publication ?Immunogenicity of novel mRNA COVID-19 vaccine MRT5500 in mice and non-human primates,? is available?here.

Shots on goal in the fight against COVID-19 In addition to the mRNA vaccine candidate in collaboration with Translate Bio, Sanofi is collaborating with GSK on a COVID-19 vaccine candidate using the same recombinant protein-based manufacturing technology as one of Sanofi?s seasonal influenza vaccines, combined with GSK?s established pandemic adjuvant platform. The Companies announced the start of the Phase 1/2 clinical trial for their adjuvanted recombinant COVID-19 vaccine candidate in September and anticipate first results in early December 2020, to support the initiation of a pivotal Phase 3 study before the end of the year.

About mRNA vaccines? Vaccines work by mimicking disease agents to stimulate the immune system, building up a defense mechanism that remains active in the body to fight future infections. mRNA vaccines offer an innovative approach by delivering a nucleotide sequence encoding the antigen or antigens selected for their high potential to induce a protective immune response. mRNA vaccines also represent a potentially innovative alternative to conventional vaccine approaches for several reasons - their high potency, ability to initiate protein production without the need for nuclear entry, capacity for rapid development and potential for low-cost manufacture and safe administration using non-viral delivery. This approach potentially enables the development of vaccines for disease areas where vaccination is not a viable option today. Additionally, a desired antigen or multiple antigens can be expressed from mRNA without the need to adjust the production process, offering maximum flexibility and efficiency in development.

About the Sanofi Pasteur and Translate Bio collaboration In 2018, Translate Bio entered into a collaboration and exclusive license agreement with Sanofi Pasteur Inc., the vaccines global business unit of Sanofi, to develop mRNA vaccines for up to five infectious disease pathogens. The agreement was first expanded in March 2020 to include development of a novel mRNA vaccine for COVID-19. In June 2020, the two Companies built upon the existing collaboration to pursue novel mRNA vaccines to broadly address current and future infectious diseases.

This collaboration brings together Sanofi Pasteur?s leadership in vaccines and Translate Bio?s mRNA research and development expertise. Under the agreement, the Companies are jointly conducting research and development activities to advance mRNA vaccines and mRNA vaccine platform development during a research term of at least four years after the original signing in 2018.

About Translate Bio Translate Bio is a clinical-stage mRNA therapeutics company developing a new class of potentially transformative medicines to treat diseases caused by protein or gene dysfunction, or to prevent infectious diseases by generating protective immunity. Translate Bio is primarily focused on applying its technology to treat pulmonary diseases caused by insufficient protein production or where the reduction of proteins can modify disease. Translate Bio?s lead pulmonary candidate is being evaluated as an inhaled treatment for cystic fibrosis (CF) in a Phase 1/2 clinical trial. Additional pulmonary diseases are being evaluated in discovery-stage research programs that utilize a proprietary lung delivery platform. Translate Bio believes that mRNA can be delivered to target tissues via multiple routes of administration and, consequently, its technology may apply broadly to a wide range of diseases, including diseases that affect the liver. Translate Bio is also pursuing the development of mRNA vaccines for infectious diseases under a collaboration with Sanofi Pasteur.