Sanofi and GSK Begin Phase 1/2 Trial of COVID-19 Vaccine Candidate with Aim to Move into Phase 3 by 2020 End

GlaxoSmithKline plc (London, UK) and Sanofi S.A. (Paris, France) have initiate Phase 1/2 clinical trial of their COVID-19 adjuvanted recombinant protein-based vaccine candidate which has shown promising safety and immunogenicity in pre-clinical studies.

The vaccine candidate, developed in partnership by Sanofi and GSK, uses the same recombinant protein-based technology as one of Sanofi’s seasonal influenza vaccines with GSK’s established pandemic adjuvant technology. Sanofi is leading the clinical development and registration of the COVID-19 vaccine. Preclinical data showed an acceptable reactogenicity profile and data based on two injections of the adjuvanted recombinant vaccine showed high levels of neutralizing antibodies that are comparable to levels in humans who recovered from the COVID-19 infection.


The Phase 1/2 clinical trial is a randomized, double blind and placebo-controlled trial designed to evaluate the safety, reactogenicity (tolerability) and immunogenicity (immune response) of the COVID-19 vaccine candidate. A total of 440 healthy adults are being enrolled in the trial across 11 investigational sites in the US. The companies anticipate first results early December 2020 which will support the initiation of a Phase 3 trial in December 2020. If data are sufficient for licensure application, the plan is to request regulatory approval in the first half of 2021.

Sanofi and GSK have entered into a collaboration with the US government to supply up to 100 million doses of their COVID-19 recombinant protein-based vaccine. The US government has a further option to discuss the purchase of up to 500 million doses longer term. Both companies have also agreed (subject to final contract) with the UK government to supply up to 60 million doses of recombinant protein-based COVID-19 vaccine. Sanofi and GSK are scaling up manufacturing of the antigen and adjuvant with the target of producing up to one billion doses in 2021.

“Sanofi and GSK bring proven science and technology to the fight against the global COVID-19 pandemic, with the shared objective of delivering a safe and effective vaccine,” said Thomas Triomphe, Executive Vice President and Global Head of Sanofi Pasteur. “The initiation of our clinical study is an important step and brings us closer to a potential vaccine which could help defeat COVID-19. Our dedicated teams and partner continue to work around the clock as we aim to deliver the first results in early December. Positive data will enable a prompt start of the pivotal Phase 3 trial by the end of this year.”

“Moving this vaccine candidate into clinical development is an important moment in the progress towards addressing the global pandemic we are all facing,” said Roger Connor, President of GSK Vaccines. “This builds on the confidence shown by governments already in the potential of this protein-based adjuvanted vaccine candidate, which utilizes established technology from both companies, and can be produced at scale by two of the leading vaccine manufacturers globally. We now look forward to the data from the study, and if positive, beginning Phase 3 by the end of the year.”

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