The Sanofi and GSK adjuvanted recombinant COVID-19 vaccine candidate achieved strong rates of neutralizing antibody responses, in line with those measured in people who have recovered from COVID-19, in all adult age groups in a Phase 2 study with 722 volunteers, the companies announced in a news release.
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, the companies added.
A global pivotal Phase 3 study is expected to start in the coming weeks.
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).
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 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 the companies expect the vaccine to be approved in the fourth quarter of 2021.
Full results of the Phase 2 study will be published in a peer reviewed journal, the companies said.
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.
