Sanofi And GSK’s Much-Delayed COVID-19 Vaccine Ready To File, But Role Looks Limited

Tipped as one of the most likely to succeed back in early 2020, the delayed development of the adjuvanted protein-based COVID-19 vaccine been humbling for both companies.

Source: Alamy

Sanofi began developing its vaccine in February 2020 and joined forces with GSK two months later

After a long and difficult development journey that started earlier but finished far behind other candidates, Sanofi and GlaxoSmithKline have announced their COVID-19 vaccine is ready for filing with regulators.

As the two biggest vaccines companies in the world when SARS-CoV-2 emerged, the partners had once been seen as a dream team. However, the combination of Sanofi’s recombinant protein-based candidate and GSK’s adjuvant stumbled at an early stage of development in late 2020, and never made up the lost ground.  (Also see "Coronavirus Update: Sanofi And GSK’s Vaccine Suffers Setback" - Scrip, 11 Dec, 2020.)

The companies have now unveiled a final analysis from global trials of the vaccine which show encouraging early results when used as a booster and 75% efficacy against moderate or severe disease when used as a primary vaccination. 

The two-dose regimen from its Phase III VAT08 study also showed 100% efficacy against severe COVID-19 disease and hospitalizations, and 57.9% efficacy against any symptomatic COVID-19 disease.

Final analysis of the global VAT02 booster trial confirmed the vaccine boosted neutralizing antibodies 18- to 30-fold across vaccine platforms (mRNA, adenovirus)

The VAT08 Phase III primary series trial recruited >10,000 participants. Two doses of the Sanofi-GSK vaccine in seronegative populations demonstrated:

• 100% efficacy against severe COVID-19 disease and hospitalizations

• 75% efficacy against moderate or severe COVID-19 disease

• 57.9% efficacy against any symptomatic COVID-19 disease, which Sanofi/GSK claim is “in line with expected vaccine effectiveness in today’s environment dominated by variants of concern”

While the results are solid and look to be more than sufficient to gain emergency use authorizations in the US and Europe, how and when the vaccine will be used remains uncertain.

Pfizer/BioNTech's and Moderna’s mRNA-based vaccines have established themselves as the most valuable tools against the pandemic (especially in western nations) having confirmed their safety and efficacy as primary shots and as boosters, even though protection was diminished against the Delta variant and even more so against Omicron.

Their dominance leaves little demand for new COVID-19 vaccines, as even when new variants emerge in future, the speed and flexibility of the mRNA platforms make them best placed to respond rapidly.

Nevertheless, Sanofi and GSK have a commitment to file the vaccine with regulators, as they received $2.1bn in upfront funding from the US government for 100 million doses, while the EU signed a purchase agreement for up to 300 million doses.

Thomas Triomphe

Thomas Triomphe executive vice president, Sanofi Vaccines, said: “The Sanofi-GSK vaccine demonstrates a universal ability to boost all platforms and across all ages. We also observed robust efficacy of the vaccine as a primary series in today’s challenging epidemiological environment.”

Triomphe added that no other global Phase III efficacy study had been undertaken during this period with so many variants of concern, including Omicron, and claimed the efficacy data were “similar” to the recent clinical data from authorized vaccines.

That claim is difficult to verify given the lack of clearly comparable studies conducted by Pfizer/BioNTech and Moderna.

Recent real-world data from South Africa found that two doses of Pfizer’s vaccine provided 70% protection against hospitalization and 33% protection against Omicron infection – a large drop from the 93% and 80% shown against Delta, but one that global booster programs have helped restore.

Sanofi had originally hoped to conduct a head-to-head pivotal study of its candidate against one of the mRNA vaccines, but the US Food and Drug Administration demanded a placebo-controlled study. In the absence of any robust head-to-head studies, public health officials look unlikely to be won over by Sanofi and GSK’s latecomer.

There could remain some opportunity for the vaccine, once approved, as a potential booster. These could be required in a post-pandemic environment if COVID-19 joins influenza in being a seasonal virus. The vaccine's non mRNA profile could also persuade some who are still COVID-19 vaccine hesitant, a hope also put forward for Novavax’s similar recombinant protein Nuvaxovid, recently approved in the EU.

For Sanofi, which announced its work on its COVID-19 vaccine in February 2020, weeks ahead of Pfizer/BioNTech and Moderna, the failure of its vaccine has been humbling. Both GSK and Sanofi are now both investing heavily in mRNA vaccine platforms to catch up with the pioneers, and both have influenza candidates based on the technology in early development.  (Also see "Sanofi Goes All The Way In mRNA With Translate Bio Buy" - Scrip, 3 Aug, 2021.)

The original version of this article was published on 24 February 2022 in Pink Sheet sister publication Scrip.