GSK, Sanofi COVID vaccine Phase 2 trial shows strong immune responses across all adult age groups

The Phase 2 interim results showed 95% to 100% seroconversion following a second injection in all age groups (18 to 95 years old) and across all doses, with acceptable tolerability and with no safety concerns. Overall, the vaccine candidate elicited strong neutralizing antibody levels that were comparable to those generated by natural infection, with higher levels observed in younger adults (18 to 59 years old). After a single injection, high neutralizing antibody levels were generated in participants with evidence of prior SARS-CoV-2 infection, suggesting strong potential for development as a booster vaccine.

"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", said Thomas Triomphe, Executive Vice President and Global Head of Sanofi Pasteur. "With these favorable results, we are set to progress to a global Phase 3 efficacy study. We look forward to generating additional data and working with our partners around the world to make our vaccine available as quickly as possible."

Roger Connor, President of GSK Vaccines added: "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. 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."

Based on these positive Phase 2 interim results, the companies plan to initiate a global Phase 3, randomized, double-blind study with the 10µg dose, in combination with GSK's pandemic adjuvant, in the coming weeks. This Phase 3 trial is expected to enroll more than 35,000 adult participants from a broad range of countries and will assess the efficacy of two vaccine formulations including the D614 (Wuhan) and B.1.351 (South African) variants.

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

Pending positive Phase 3 outcomes and regulatory reviews, the vaccine is expected to be approved in the fourth quarter of 2021.

The Phase 2 study interim results show that the adjuvanted recombinant vaccine candidate triggered strong immune response amongst adults of all age groups with 95% to 100% seroconversion rates and neutralizing antibodies that were comparable to those generated by natural infection. The high titers observed in the non-naïve population after one dose of the vaccine candidate also suggest it may have strong potential for use as a booster vaccine.

The randomized, double-blind, multi-center-dose-ranging study was conducted in healthy adults aged 18 years of age and older, including those with high risk medical conditions, to evaluate the safety, reactogenicity, and immunogenicity of two injections given 21 days apart, with 3 antigen dose levels of 5, 10 and 15 µg. Beginning in February 2021, the study enrolled 722 volunteers in the U.S. and Honduras. It included equivalent numbers of adults 18 to 59 years and those 60 years and above.

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