Sanofi’s first mRNA vaccine shows neutralising antibody seroconversion

Sanofi have announced positive Phase I/II study interim results for its first messenger RNA (mRNA)-based COVID-19 vaccine candidate. The development of the vaccine involved the use of the recently-acquired Translate Bio’s mRNA and lipid nanoparticle (LNP) platform and is part of Sanofi’s mRNA strategy.

The initial data from Phase I/II showed neutralising antibody seroconversion (defined as four-fold increase versus baseline) in 91 to 100 percent of study participants, two weeks after a second injection, across all three dosages tested. According to Sanofi, no safety concern has been observed and the tolerability profile is comparable to that of other unmodified mRNA COVID-19 vaccines. Further data from this first study of Sanofi’s mRNA platform will be presented at a later date.

Targeting 2022 initiation of its clinical studies for an influenza vaccine with modified mRNA, Sanofi launched a Phase I clinical trial in June 2021 evaluating an mRNA-based investigational vaccine against seasonal influenza. The trial will evaluate the safety and immunogenicity of a monovalent flu vaccine candidate encoding the hemagglutinin protein of the A/H3N2 strain of the influenza virus across two formulations (MRT5400 and MRT5401) with different LNPs.

At the same time, Sanofi is also continuing to develop its adjuvanted recombinant protein candidate vaccine in partnership with GlaxoSmithKline (GSK). In parallel to its ongoing Phase III efficacy and safety study, Sanofi’s development programme now includes a study of the vaccine as a potentially broadly protective booster to address evolving public health needs.

Recently published pre-clinical data indicated the candidate has the potential to strongly boost immune responses following primary vaccination across multiple vaccine technology platforms and against a broad spectrum of variants of concern. The booster studies began this summer in the US, Australia, France and the UK.

“We are happy to see those positive initial results,” stated Jean-Francois Toussaint, Global Head of Research and Development at Sanofi Pasteur. “These results will clearly help inform the path forward for our mRNA development programs. Today, we have a promising mRNA platform, which we are taking to the next level in development, including moving to modified mRNA, and against other diseases, including flu.”