Positive Phase II Results for Sanofi/GSK Covid-19 Vaccine

Sanofi and GSK reported positive data on their COVID-19 vaccine candidate in all adult age groups in its Phase II trial of 722 volunteers. They expect to launch a global pivotal Phase III trial in the coming week.

The two companies were leveraging a traditional vaccine approach, much like their annual flu vaccine. Still, their early start ran into delays when it failed to demonstrate effectiveness in older individuals. 

On December 11, 2020, they reported the delay after patients 50 and older demonstrated an “insufficient immune response.” They announced plans to refine the concentration of the antigen in the vaccine. Then in February, they launched the Phase II trial of an updated version of their adjuvanted recombinant protein-based vaccine.

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The Phase II interim data demonstrated 95% to 100% seroconversion after the second injection in all age groups, ranging from 18 to 95. There were no safety concerns, and tolerability was acceptable. They found it provided strong neutralizing antibody levels similar to that seen in people who recovered from COVID-19, with higher levels in younger adults ages 18 to 59. And after one injection, high neutralizing antibody levels were seen in patients with evidence of previous SARS-CoV-2 infection, which the companies say suggests “strong potential for development as a booster vaccine.”

“Our Phase II 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 III 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.”

The two companies have probably missed out on the market for affluent countries, where Pfizer–BioNTech, Moderna, AstraZeneca-Oxford, and Johnson & Johnson have been broadly distributed for months in Western countries. Still, there’s a need for vaccines in many other parts of the world, particularly in less-affluent countries. 

The attention Triomphe brings to the possibility of the vaccine being used as a versatile “universal booster” suggests a potential strategy. In a media call, he said, “We know the world today needs more than one platform, it needs the flexibility of different platforms, different manufacturing and distribution to address the global need all around us.”

Of course, both AstraZeneca-Oxford and Johnson & Johnson have had difficulties with safety issues, primary rare blood clotting events, even though public health officials and biostatisticians indicate the safety issues are significantly less than compared to the risks of COVID-19.

The companies hope to have resulted from the Phase III trial, which expects to enroll 35,000 volunteers by the fourth quarter. 

Sanofi is providing manufacturing support to Moderna, Pfizer-BioNTech, and Johnson & Johnson on their COVID-19 vaccines. It is also developing an mRNA vaccine in partnership with Translate Bio, which is expected human data in the third quarter this year.

Triomphe pointed out that Sanofi’s vaccines will be manufactured and distributed on a separate supply chain than those manufacturing efforts. Still, he also said it was too early to estimate manufacturing capacity. He did hint at the conference call that if their vaccine comes together, they may shift those partnerships when their various manufacturing contracts end.