- Sanofi and GlaxoSmithKline on Monday reported a coronavirus vaccine they developed together met the goal of a mid-stage clinical trial, boosting the companies' research efforts five months after an earlier version of the shot disappointed in a costly setback.
- Results from the trial, which enrolled 722 volunteers in the U.S. and Honduras, showed the revamped vaccine spurred immune responses that were comparable to what researchers have observed following naturally occurring cases of COVID-19. Importantly, the companies said responses were strong across age groups, including in older adults whose immune systems tend to be weaker.
- Sanofi and GSK now plan to launch a Phase 3 study of the vaccine in the "coming weeks" and expect to enroll some 35,000 adult volunteers from a "broad range of countries." Doing so will be harder than six months ago, however, after multiple other vaccines have been made available in many countries in North America, Europe and the Middle East.
Sanofi and GSK, two of the world's biggest vaccine makers, have watched as Pfizer, Moderna and other rival developers claimed victory with safe and effective coronavirus shots. Late to get started with testing of their own candidate, the companies' trial setback in December forced them to redesign their vaccine and cost them months of delay.
Monday's results are a promising sign their second effort could fare better. The Phase 2 study tested the shot's safety and measured participants' immune response to vaccination. Mid-stage trials of other vaccines were designed similarly.
According to the companies, between 95% and 100% of volunteers "seroconverted," or had a detectable immune response, following two injections spaced three weeks apart. That range applied across ages — participants were anywhere from 18 to 95 years old — and across each of the low, middle and high doses tested in the study.
Sanofi and GSK haven't yet disclosed detailed data such as the exact amount of neutralizing antibodies — the immune cell defenders against viral infection — observed in vaccinated volunteers. But the partners indicated levels of neutralizing antibodies were similar to those following natural infection and higher in younger participants.
There were no safety concerns, the companies said, and reaction rates to vaccination were "acceptable." Vaccines developed by Pfizer and Moderna, for comparison, often cause mild-to-moderate injection site pain, headache, fever or tiredness.
The shot's performance on both measures — safety and immune response — is reassuring as Sanofi and GSK's first formulation appeared less potent in older adults and was associated with higher-than-expected levels of side effects.
"Our Phase 2 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, head of Sanofi's vaccine division.
The companies will test the middle dose from Phase 2 in a large, Phase 3 trial. That study will assess a formulation aimed at the original coronavirus strain as well as a variant first identified in South Africa associated with weaker vaccine potency. Results, and subsequent authorizations, could come as soon as the fourth quarter, Sanofi and GSK said, setting an ambitious timeline.
Sanofi and GSK's partnership, an unusual tie-up of rivals, drew substantial attention last year as vaccine development efforts around the world got underway. The companies, both experienced, global vaccine manufacturers, aimed to design a protein-based shot using well-established technologies. The U.S. government pledged $2.1 billion to testing and manufacturing of the vaccine, and contracted to buy 100 million doses.
Now, however, the U.S. may not need Sanofi and GSK's vaccine, or at least large quantities of it, after widespread roll-out of Pfizer's and Moderna's shots, the availability of a third from Johnson & Johnson and others potentially on the way. Nearly 60% of adults over 18 have received at least one vaccine dose, according to data from the Centers for Disease Control and Prevention.
Sanofi and GSK's vaccine, though, could still play a role in less developed countries that don't have access to the existing shots. The drugmakers signed one of the larger supply deals with the international vaccine alliance COVAX, and their vaccine can be shipped and stored at room temperature, unlike the freezer requirements for Pfizer's and Moderna's.
The partners may aim to position their vaccine as a booster, helping maintain coronavirus immunity already established by previous infection or vaccination. The companies said results following a single injection in previously infected trial volunteers showed high antibody levels, potentially suggesting the utility of a booster shot.
The two drugmakers also plan to conduct further studies to better assess whether a low dose of their vaccine could boost immune responses regardless of which shot people initially received.
Widespread availability of vaccines could complicate Sanofi and GSK's plans for their Phase 3 trial, though, as people may be reluctant to volunteer for a clinical trial when they can choose an already proven shot. That's already the case in the U.S., U.K., large swaths of Europe and several other nations like Israel. In many other countries, which do not yet have sufficient vaccines supplies, a trial may be more logistically feasible.
Moreover, randomizing trial participants to receive a placebo in a vaccine trial may not be ethical if authorized vaccines are available.
A spokesperson for Sanofi confirmed the trial would be placebo-controlled and said the companies would target countries in Latin America and in Asia for enrollment.
"Some countries are definitely much further ahead than others in terms of vaccines' distribution, but there are still many parts of the world where there is insufficient vaccine, where there is a strong desire to also participate in this placebo-controlled Phase 3 trial," he said.
Sanofi and GSK plan to publish results from their Phase 2 study in a peer-reviewed medical journal.
Note: This story has been updated with comment from Sanofi.