GlaxoSmithKline and Sanofi announced Thursday the start of enrollment in a phase 3 study investigating their adjuvanted recombinant-protein COVID-19 vaccine candidate, according to a FirstWord report. The trial will include more than 35,000 volunteers aged 18 and older from several countries, including sites in the US, Asia, Africa and Latin America.
The start of the study comes shortly after the companies announced results from a mid-stage trial of adults showing that the vaccine triggered neutralizing antibody levels that were comparable to those generated by natural infection. In addition, the vaccine induced a “strong” immune response following a second injection, with 95% to 100% seroconversion rates.
GlaxoSmithKline and Sanofi noted that the placebo-controlled phase 3 study will initially investigate the efficacy of a vaccine formulation targeting the original D.614 virus that was first identified in Wuhan, China, while a second stage will evaluate another formulation targeting the B.1.351 variant, which was first detected in South Africa. The trial’s primary endpoint is the prevention of symptomatic COVID-19 in SARS-CoV-2 naïve adults, with secondary goals being the prevention of severe COVID-19 disease and prevention of asymptomatic infection.
The drugmakers noted that if the study is positive, the vaccine could be authorized in the fourth quarter, while manufacturing will soon commence in preparation for a potential launch. They added that studies will also begin in the coming weeks 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.
The companies began working together on a COVID-19 vaccine in April last year, combining Sanofi’s recombinant antigen and GlaxoSmithKline’s pandemic adjuvant. However, the drugmakers faced a delay after reporting that a low immune response was seen in older adults in a phase 1/2 study “due to an insufficient concentration of the antigen,” prompting them to start investigating an improved antigen formulation.