GSK takes SK bio-partnered COVID jab into phase 3

As a top vaccine maker, GlaxoSmithKline has been a laggard in the COVID-19 vaccine race, but has put on a late burst of speed with a start of phase 3 trials of a second candidate that will be compared directly to the AstraZeneca shot.

The move follows phase 1/2 results with SK bio’s GBP510, which found that it stimulated neutralising antibodies against SARS-CoV-2 in all 80 recipients, with no safety issues recorded. Neutralising antibody titres in the blood were five to eight times higher than people who recovered from COVID-19.

The trial will enrol around 4,000 participants from a range of countries and will compare GBP510’s safety and immunogenicity to AZ/Oxford University’s Vaxzevria vaccine.

The vaccine – based on a self-assembling protein nanoparticle that displays 60 copies of the SARS-CoV-2 spike protein – is formulated with GlaxoSmithKline’s vaccine adjuvant, designed to boost the immune response.

In the phase 3 study around 3,000 subjects will get two doses of GB510, while the remainder will receive two doses of Vaxzevria, both given four weeks apart.

“The aim is for global supply through the COVAX facility in the first half of 2022, subject to data and regulatory review,” said GSK in a statement this morning.

COVAX is a World Health Organisation-backed vaccine-sharing project that aims to address the imbalance that has seen the world’s high income nations snap up the first approved vaccines, and has set a target of delivering about two billion vaccine doses globally by the end of the year.

“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 GSK’s chief global health officer Thomas Breuer.

“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,” he added

GBP510 is the second COVID-19 vaccine with which GSK is involved. It is also supplying its adjuvant for use with a Sanofi-partnered shot –  called Vidprevtyn and based on a recombinant protein antigen – which started a 35,000-patient phase 3 trial in May.

Vidprevtyn is already under rolling regulatory review by the EU regulator, and is unusual among COVID-19 vaccines because the first dose targets the original ‘wild-type’ SARS-CoV-2 virus while the second targets a variant of concern – namely the beta (B.1.351) strain first identified in South Africa.

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