GlaxoSmithKline (GSK) and SK bioscience have launched a Phase III trial of their adjuvanted COVID-19 vaccine candidate, which is set to compare the jab to AstraZeneca’s (AZ) vaccine.

The trial, which will enrol around 4,000 participants from various countries, will aim to evaluate SK’s COVID-19 vaccine candidate GBP510 in combination with GSK’s pandemic adjuvant.

The study will investigate GBP510’s safety and immunogenicity compared to AZ’s Oxford University-partnered COVID-19 vaccine, which will act as an active comparator in the trial.

According to GSK/SK, the study is one of the first global Phase III trials to compare two different COVID-19 vaccine candidates.

The launch of the Phase III trial comes following positive interim Phase I/II trial data, which showed that all participants who received the jab developed strong neutralising antibody response, with a 100% seroconversion rate.

On top of that, neutralising antibody titres were found to be between five and a maximum of eight times higher in individuals who had received GSK/SK’s vaccine compared to the sera from people who had recovered from COVID-19.

“While many countries have made good progress with vaccination, there remains a need for accessible and affordable COVID-19 vaccines to ensure equitable access and to protect people across the world,” said Thomas Breuer, chief global health officer, GSK.

"We are grateful that we were able to advance to the Phase III study with the unprecedented support of global initiatives, including GSK, Coalition for Epidemic Preparedness Initiative (CEPI), and the Bill & Melinda Gates Foundation (BMGF). Taking this important step towards overcoming the global pandemic situation, SK and GSK will bring our technical expertise together for the development of an adjuvanted protein-based vaccine candidate, GBP510,” added Jaeyong Ahn, chief executive officer of SK bioscience.

GSK and SK are expecting results from the late-stage study in the first half of 2022 – if the trial yields positive results and wins regulatory approval, the companies are hoping the jab can be supplied ‘at scale’ through the COVAX vaccines sharing facility.