- Sanofi and GlaxoSmithKline on Monday announced the start of a Phase 2 study testing a new version of the experimental coronavirus vaccine the two partners have been developing.
- The 720-volunteer mid-stage study begins roughly two months after the partners disclosed weaker than expected results for their first vaccine candidate. Sanofi and GSK are evaluating a "refined antigen formulation" in the new trial, and could start Phase 3 testing in the second quarter if results are positive, they said in a statement.
- If all goes well, Sanofi and GSK hope to bring a vaccine to market by the fourth quarter of 2021. But that outcome would still represent a six-to-nine month delay from previous estimates, a significant setback for a program that was promised up to $2.1 billion in funding from the U.S. government. Multiple coronavirus vaccines are already available, and others could arrive later this year.
It's a different world today than 10 months ago, when Sanofi and GSK formed their alliance to co-develop a coronavirus vaccine.
Then, experimental vaccines from Moderna and partners Pfizer and BioNTech were just beginning human testing. The messenger RNA technology they relied on was unproven, making the more traditional, protein-based approach championed by Sanofi and GSK seem like a safer bet. And hopes for a safe and effective vaccine in less than a year still seemed optimistic.
Events since then defied many of those expectations. Moderna, as well as Pfizer and BioNTech, proved their vaccines more than 90% effective at preventing symptomatic COVID-19 in clinical testing. Shots from Johnson & Johnson, Novavax and AstraZeneca — as well as from developers in China and Russia — have been found to prevent disease and are either soon to be authorized or already are.
Sanofi and GSK, meanwhile, scrapped their first vaccine in December after observing weak immune responses and "higher than expected levels" of adverse events in elderly trial volunteers. The companies blamed a likely "insufficient concentration of the antigen" in the vaccine, and said an improved formulation had shown better prospects in animal tests.
The update has relegated Sanofi and GSK, two of the world's largest vaccine makers, to a largely supporting role in the pandemic. While resetting its program, Sanofi has agreed to help Pfizer and J&J make more doses of their vaccines, offering to lend its pharmaceutical peers spare production capacity at manufacturing plants in Europe. GSK has expanded partnerships with CureVac and Vir Biotechnology on different coronavirus vaccines and drugs.
Sanofi and GSK's program could still play a role in curbing COVID-19 across the globe. Even with multiple shots available, vaccine supply remains scarce and is likely to remain so for much of the year for many countries outside of the U.S. and Europe. Sanofi and GSK's shot is more easily shipped and stored than Moderna's and Pfizer's. The U.S. has secured 100 million doses, and the international vaccine alliance COVAX — which is distributing vaccines to low- and middle-income countries — has pre-ordered 200 million, one of its largest deals.
Those deals will only matter, however, if Sanofi and GSK's new shot can succeed where the previous version failed and produce meaningful results in both young and elderly participants.
The upgraded shot will be tested in a more challenging environment, though. Virus variants with the potential to diminish a vaccine's potency are now circulating in several countries — among them the U.S., which is one of the sites for Sanofi and GSK's Phase 2 study. The trial will include just as many volunteers over 60 years of age as under, and will test three different antigen doses with a fixed dose of an immune-boosting adjuvant.
"We are confident that our vaccine candidate has strong potential and we are very encouraged by the latest preclinical data," said Thomas Triomphe, the executive vice president and head of Sanofi Pasteur, in a statement.
Sanofi and GSK will move quickly if the vaccine appears safe and generates meaningful immune responses. A Phase 3 trial would start between April and June, and if successful, could lead to availability in the fourth quarter.
The two companies have also begun work studying coronavirus variants. That research will help inform the next stages of their development program, they said.