Sanofi Pasteur has initiated a Phase I clinical trial evaluating a messenger RNA (mRNA)-based investigational vaccine for seasonal influenza. The US-based trial will assess the safety and immunogenicity of several dose levels of a monovalent flu vaccine in up to 280 healthy adults.

The monovalent vaccine candidate encodes the hemagglutinin protein of the A/H3N2 strain of the influenza virus. Flu seasons that are dominated by A/H3N2 strain circulation tend to be more severe, especially among those considered at-risk such as older adults and younger children.

“The first clinical trial of a seasonal mRNA flu vaccine candidate is an exciting milestone in our quest for the next generation of influenza vaccines. We have all witnessed the promise of mRNA technology during this pandemic and are now looking to extend that promise to select annual vaccines,” commented Jean-Fran?ois Toussaint, Global Head of Research and Development, Sanofi Pasteur. “We look forward to sharing initial results by year-end.”

“We are pleased to have this second mRNA vaccine program underway with our partner Sanofi Pasteur,” said Ronald Renaud, chief executive officer of Translate Bio. “We believe that mRNA technology could have several advantages for a seasonal flu application including the potential ability to demonstrate robust immune responses based on pre-clinical data to date, enable antigen specificity within a short timeframe from seasonal virus strain selection, and deploy agile manufacturing capacity. We look forward to evaluating the potential of these mRNA influenza vaccine candidates in this Phase I clinical trial.”

Sanofi and Translate Bio have developed and will evaluate two formulations of the vaccine (MRT5400 and MRT5401) in the clinical trial. The two formulations differ in the lipid nanoparticle (LNP) that contains the mRNA.

The trial follows successful preclinical research which demonstrated promising safety and immunogenicity, the results were presented at the 8th annual mRNA Healthcare Conference in November 2020.

About the Sanofi Pasteur and Translate Bio collaboration

In June 2018, Translate Bio entered into a collaboration and exclusive license agreement with Sanofi Pasteur, the vaccines 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 agreement to pursue novel mRNA vaccines to broadly address current and future infectious diseases. There are two ongoing mRNA vaccine clinical trials under the collaboration, one for COVID-19 and one for influenza.