GSK, Sanofi COVID-19 Vaccine Elicits Strong Antibody Response

May 21, 2021 - GSK and Sanofi’s COVID-19 vaccine candidate achieved strong rates of neutralizing antibody responses in a Phase 2 clinical trial, according to a recent press release.

The Phase 2 trial enrolled 722 volunteers 18 to 95 years of age. Interim results from the trial showed 95 to 100 percent seroconversion following a second injection in all age groups and across all doses.

The vaccine candidate elicited strong neutralizing antibody levels that were comparable to those generated by natural infection. Higher levels were seen in younger adults.

Additionally, higher neutralizing antibody levels were observed in participants with evidence of prior COVID-19 infection, which suggests strong potential for development as a booster vaccine, a GSK spokesperson explained.

Notably, there were no safety concerns.

“These positive data show 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,” Roger Connor, president of GSK, said in the announcement.

“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,” Connor continued.

Based on the positive results, GSK and Sanofi will initiate a global Phase 3 randomized, double-blind trial in the coming weeks. Nearly 35,000 adult participants from various countries will receive 10 micrograms in combination with GSK’s pandemic adjuvant.

In the trial, researchers will assess the efficacy of two vaccine formulations, including the Wuhan strain, D614, and the South African strain, B.1.351.

The COVID-19 vaccine is expected to be FDA approved in the fourth quarter of 2021, based on positive Phase 3 outcomes and regulatory reviews.

"Our Phase 2 data confirm the potential of this vaccine to play a role in addressing this ongoing global public health crisis, as we know multiple vaccines will be needed, especially as variants continue to emerge and the need for effective and booster vaccines, which can be stored at normal temperatures, increases,” Thomas Triomphe, executive vice president and head of Sanofi, said in the announcement.

“With these favourable results, we look forward to generating additional data and working with our partners around the world to make our vaccine available as quickly as possible,” Triomphe continued.

GSK and Sanofi developed their COVID-19 vaccine in June 2020 using protein-based technology from Sanofi, which was key to producing an influenza vaccine in the past. The vaccine also leveraged GSK’s pandemic adjuvant technology.

So far, the UK has secured 60 million doses of the vaccine and Europe has secured 300 million doses.

The companies intend to conduct booster studies with various variant formulations to assess the ability of a lower dose of the vaccine to generate a strong booster response, regardless of the initial vaccine platform received.

B.1.351 was first reported in South Africa in December 2020 and has been detected in at least nine states in the US since the end of January 2021.

Currently, NIH is conducting a Phase 1 clinical trial evaluating Moderna’s variant-specific COVID-19 vaccine candidate, mRNA-1273.351, against B.1.351.

mRNA-1273.351 delivers instructions for making the SARS-CoV-2 spike that incorporates key mutations in the B.1.351 virus variant. Volunteers in the trial will provide blood samples at specified times, which will be used to measure the immune response against B.1.351.

The trial will enroll 210 healthy adult volunteers at four clinical research sites in the US, as well 150 volunteers aged 18 to 55 years who have not received any COVID-19 vaccine, have no known history of SARS-CoV-2 infection, and do not have health conditions that are associated with an increased risk of severe illness.