SK bioscience and GlaxoSmithKline (GSK) have launched a Phase III clinical trial to assess the safety and immunogenicity of the former’s Covid-19 vaccine candidate, GBP510.

A self-assembled nanoparticle vaccine, GBP510 is adjuvanted with GSK’s pandemic adjuvant. The vaccine candidate targets the SARS-CoV-2 Spike protein’s receptor-binding domain.

SK bioscience is developing the antigen in partnership with the Institute for Protein Design (IPD) at the University of Washington.

The randomised, active-controlled global Phase III trial will compare the vaccine candidate to AstraZeneca-Oxford University Covid-19 vaccine. This marks the trial as one of the first international Phase III studies comparing two different Covid-19 vaccines.

It will enrol approximately 4,000 subjects in multiple countries.

According to interim results from the ongoing Phase I/II trial, GBP510 led to a 100% seroconversion rate, with all subjects who received the adjuvanted vaccine developing robust neutralising antibody responses.

When compared with sera from patients who recovered from Covid-19, GBP510-generated neutralising antibody titres were greater by five to eight times.

The Phase I/II trial did not reveal any safety issues with the vaccine candidate.

Data from the Phase III trial are anticipated in the first half of next year. If positive results and regulatory approval are obtained, the companies intend to supply the vaccine at scale globally through the COVAX facility.

GSK chief global health officer Thomas Breuer said: “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.

“We are pleased to contribute with GSK’s pandemic adjuvant and to be working with SK to deliver the vaccine at scale via COVAX if it is approved.”

In May 2021, SK bioscience announced funding of up to $173.4m (KRW200bn) from the Coalition for Epidemic Preparedness Innovations (CEPI) to support the Phase III trial of GBP510.

Earlier this month, the company secured approval from South Korea’s Ministry of Food and Drug Safety to study the vaccine in a Phase III trial.