Sanofi Pasteur and Translate Bio have commenced a Phase I clinical trial in the US to assess an investigational messenger ribonucleic acid (mRNA)-based vaccine candidate against seasonal influenza.

The monovalent flu vaccine candidate codes for the hemagglutinin protein of the influenza virus’s A/H3N2 strain.

Sanofi noted that flu seasons with the A/H3N2 strain in circulation are likely to be severe, particularly in older adults and younger children, who are at an increased risk.

The Phase I trial will analyse the safety and immunogenicity of the influenza vaccine in up to 280 subjects, with preliminary results expected by year-end.

Various dose levels of two formulations of the vaccine, MRT5400 and MRT5401, will be evaluated in healthy adults aged 18 and 49.

The formulations, which were developed by the companies, vary in the lipid nanoparticle (LNP) that comprises the mRNA.

Translate Bio CEO Ronald Renaud said: “We are pleased to have this second mRNA vaccine programme underway with our partner Sanofi Pasteur.

“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 preclinical data to date, enable antigen specificity within a short timeframe from seasonal virus strain selection, and deploy agile manufacturing capacity.”

The Phase I trial comes after favourable safety and immunogenicity data were observed in preclinical studies reported in November last year.

Translate Bio signed a collaboration and exclusive licence agreement with Sanofi Pasteur in June 2018 to develop mRNA vaccines for up to five pathogens causing infectious diseases.

The companies expanded the deal in March last year, to develop a new mRNA Covid-19 vaccine.

In June last year, Translate Bio and Sanofi Pasteur agreed to create mRNA vaccines that could be used against existing and emergent infectious diseases.

At present, the companies are conducting two clinical trials of two mRNA vaccines for Covid-19 and influenza, respectively.