Sanofi and GlaxoSmithKline (GSK) have delayed their COVID-19 vaccine programme after their jointly developed candidate induced a low immune response in older adults.
An interim analysis of results from a phase 1/2 study of Sanofi/GSK’s adjuvanted recombinant protein-based COVID-19 vaccine showed an immune response in vaccinated participants aged 18-49 years that was similar to recovered COVID-19 patients.
In elderly participants, however, the immune response observed was low, likely caused by an ‘insufficient concentration’ of the antigen component of the vaccine, the companies said in a statement.
Sanofi/GSK have now rescheduled their previous timeline for the vaccine, with a new plan to launch a phase 2b study in February 2021.
The phase 2b study will now test an improved antigen formulation, after a recent challenge study in non-human primates showed that this new formulation could protect against lung pathology.
The improved antigen also lead to rapid viral clearance from the nasal passages and lungs within two to four days in the animal challenge study.
“We care greatly about public health, which is why we are disappointed by the delay, but all our decisions are and will always be driven by science and data. We have identified the path forward and remain confident and committed to bringing a safe and efficacious COVID-19 vaccine,” said Thomas Triomphe, Executive Vice President and Head of Sanofi Pasteur.
“Following these results and the latest encouraging new preclinical data, we will work to further optimise our candidate to achieve this goal. No single pharma company can make it alone; the world needs more than one vaccine to fight the pandemic,” he added.
The delay will be a blow to the COVAX facility, a global mechanism designed to ensure joint procurement and a pooling of the risk across multiple vaccine candidates.
In October Sanofi/GSK signed an agreement with Gavi, the legal administrator of COVAX, to make 200 million doses of their vaccine available to the facility.
“The delay is a bitter blow for poorer nations, given that Sanofi-GSK was set to provide nearly one third of COVAX doses – the global vaccine purchasing facility upon which many of the poorest countries depend,” said Julia Heres Garcia, global health and gender equality officer, Oxfam.
Following the delay, Sanofi/GSK now plan to include a proposed comparison with an authorised COVID-19 vaccine in their phase 2b study.
Depending on whether the data from this mid-stage study is positive, Sanofi/GSK could be ready to begin a global phase 3 study in mid-2021.
If the vaccine scores positive results in the late-stages of testing, the companies intend to submit it to global regulators in the second half of 2021, meaning the vaccine will not be available until at least the second half of 2021.