Sanofi and GlaxoSmithKline (GSK) have announced that their delayed COVID-19 vaccine generated strong rates of neutralising antibody responses in a mid-stage trial.
The phase 2 trial enrolled 722 participants in the US and Honduras and included equivalent numbers of adults aged 18 to 59 and those aged 60 and above.
In this trial, the immune responses generated by Sanofi/GSK’s adjuvanted recombinant protein-based vaccine were in line with those measured in people who have recovered from COVID-19, the companies said in a statement.
In addition, the interim results showed 95-100% seroconversion following a second injection across all adult age groups in the trial and across all doses.
High neutralising antibody titres were also observed in participants with evidence of prior COVID-19 infection, suggesting the vaccine candidate may have the potential to be deployed as a booster vaccine.
“[This] positive data shows the potential of this protein-based adjuvanted vaccine candidate in the broader context of the pandemic, including the need to address variants and to provide for booster doses,” said Roger Connor, president of GSK Vaccines.
“We believe that this vaccine candidate can make a significant contribution to the ongoing fight against COVID-19 and will move to phase 3 as soon as possible to meet our goal of making it available before the end of the year,” he added.
Last December, Sanofi and GSK delayed their COVID-19 vaccine programme after their jointly developed candidate induced low immune responses in older adults in a phase 1/2 study.
Although the vaccine was able to generate a similar immune response to recovered COVID-19 vaccine patients in participants aged 18-49, in elderly participants the immune response observed was low.
At the time, the companies said these results was likely caused by an ‘insufficient concentration’ of the antigen component of the vaccine.
Following these positive results, Sanofi and GSK are planning to begin a global phase 3 trial in the coming weeks.
The study will enrol more than 35,000 participants from a number of countries and will assess the efficacy of two vaccine formulations, including the D614 (Wuhan) and B.1.351 (South African) variants.
The companies will also conduct booster studies in parallel to the phase 3 trial, testing various variant formulation to assess if a lower dose of Sanofi/GSK vaccine can generate a strong booster response, regardless of the initial vaccine platform received.