Sanofi and GlaxoSmithKline (GSK) have commenced a new Phase 2 trial of its adjuvanted mRNA-based Covid-19 vaccine candidate in 720 volunteers, aged 18 and older.

The new Phase 2 trial is designed to determine the appropriate antigen dosage for Phase 3 evaluation of their adjuvanted Covid-19 vaccine candidate.

Sanofi and GSK initially entered into a collaboration in April 2020, to develop an adjuvanted Covid-19 vaccine using technology from both companies.

Under the partnership, Sanofi contributes its recombinant antigen and GSK its pandemic adjuvant, both established vaccine platforms that showed effectiveness against influenza.

Sanofi Pasteur executive vice president Thomas Triomphe said: “Over the past few weeks, our teams have worked to refine the antigen formulation of our recombinant-protein vaccine, based on learnings from our initial Phase 1/2 study.

“We are confident that our vaccine candidate has strong potential and we are very encouraged by the latest preclinical data. This new Phase 2 study will enable us to identify the final vaccine formulation for adults of all ages.

“We have demonstrated our commitment to focusing efforts and capabilities towards the global fight against the pandemic, and this new study takes us a step closer to achieving our primary goal of developing a Covid-19 vaccine with a good efficacy and safety profile.”

The new Phase 2 trial is a randomised, double-blind, multi-centre dose-finding study, designed to evaluate the safety, reactogenicity, and immunogenicity of the two-dose vaccine.

The study will test three different antigen doses with a fixed dose of adjuvant, in a total of 720 study volunteers, across the US, Honduras and Panama. The results from the Phase 2 study will be used to frame the Phase 3 protocol.

Along with the new Phase 2 study, the partnership will recognise the global emergence of new SARS-CoV-2 variants and their potential impact on vaccine efficacy.

The Phase 1/2 study results, announced in December 2020 showed an immune response similar to patients recovered from Covid-19 in adults aged 18 to 49 years.

The clinical trial programme is supported by the US Biomedical Advanced Research and Development Authority (BARDA).

GSK Vaccines president Roger Connor said: “We are pleased to be starting this new Phase 2 study. The world needs multiple vaccines and we are confident that combining our proven pandemic adjuvant system with this improved antigen formulation will have significant potential as the pandemic evolves.

“We look forward to further progressing this vaccine candidate to Phase 3 in Q2 2021, if this Phase 2 study is successful.”