The study will evaluate two vaccine formulations: one against the original D.614 (Wuhan) virus and one against the B.1.351 (South Africa) variant.
The global, randomized, double-blind placebo-controlled Phase 3 study will include more than 35,000 volunteers aged 18 and older from several countries, including sites in the US, Asia, Africa, and Latin America.
A booster study will also complement the Phase 3 trial.
The primary endpoint of the study is the prevention of symptomatic COVID-19 in SARS-CoV-2 naïve adults, with secondary endpoints being the prevention of severe COVID-19 disease and prevention of asymptomatic infection.
The study will initially investigate the efficacy of a vaccine formulation targeting the original D.614 virus (Wuhan), while a second stage will evaluate a second formulation targeting the B.1.351 (South African) variant.
“Recent scientific evidence shows that antibodies created against the B.1.351 variant may provide broad cross-protection against other more transmissible variants,” note the companies, referencing a pre-print study published in March. “The design of the Phase 3, conducted across a broad diversity of geographies, also allows evaluation of the efficacy of the candidate against a variety of circulating variants."
In the coming weeks, the companies will also begin clinical studies to assess the ability of the adjuvanted recombinant-protein COVID-19 vaccine candidate to generate a strong booster response regardless of initial vaccine platform received.
Sanofi and GSK partnered up early in the pandemic to develop a adjuvanted recombinant protein-based vaccine, using Sanofi’s recombinant antigen and GSK’s pandemic adjuvant – both established platforms successful against influenza.
The project, however, suffered a setback in December when the companies announced the vaccine had shown an insufficient immune response in older people.
A refined antigen formulation entered Phase 2 trials in February. Interim results showed the high rates of neutralizing antibody responses in all adult age groups, with 95 to 100% seroconversion rates.
“After a single injection, high neutralizing antibody levels were also generated in participants with evidence of prior SARS-CoV-2 infection, suggesting strong potential for development as a booster vaccine.”
The companies continue to plan for authorization in Q4, 2021: and manufacturing will begin in the coming weeks to enable rapid rollout should it be approved.