By Jenny Strasburg 

Sanofi SA and GlaxoSmithKline PLC said their Covid-19 vaccine candidate showed positive interim trial results and is expected to move into large-scale human trials soon, putting the long-delayed shot on track for potential regulatory approval later this year.

France's Sanofi and GSK, based in the U.K., said Monday the two-dose shot produced strong antibody responses in phase-two trials with 722 volunteers. A single dose generated high levels of antibodies in volunteers with evidence of prior Covid-19 infection, the companies said, suggesting the vaccine could be useful as a booster for people already vaccinated with other shots.

Now the companies plan to begin pivotal phase-three trials, which will involve more than 35,000 people, and use two formulations: one targeting the original Covid-19 strain that circulated last year, and the second aimed at the strain that was originally detected in South Africa.

Sanofi and GSK fell behind other vaccine makers last year when they abandoned previous human trials after a miscalculation in the manufacturing process resulted in erroneously lower doses.

Their partnership combines a Sanofi-owned antigen -- a protein from the coronavirus that triggers an immune response -- and a GSK-owned adjuvant, a molecule used in some vaccines to boost the level of protection. The mis-dosing required the vaccine to be reformulated for new clinical trials.

The vaccine's long development delay raised questions among investors and health officials about the shot's potential role in fighting the pandemic, given the availability of other vaccines already proven effective. U.S. and European officials previously expected the shot to play a core role in vaccination campaigns by early this year.

Sanofi and GSK said Monday they see a need for additional vaccines to fight new virus variants and provide boosters to renew protection from prior vaccinations.

One challenge for the companies might be recruiting tens of thousands of trial volunteers who haven't already been vaccinated, with an adequate mix of ages, geographic locations and other factors that regulators consider when evaluating large-scale trial results, analysts at UBS said in a research note Monday.

The drugmakers didn't provide detailed efficacy results from the smaller-scale trails, but said volunteers in all age groups, ranging from 18 to 95 years old, showed disease-fighting antibody levels comparable to those generated by natural Covid-19 infection. The companies said the full interim trial results will be reviewed by independent researchers and published.

The vaccine can be stored using normal refrigeration, an advantage compared with ultracold temperature requirements of some shots.

GSK is also working with German biotechnology company CureVac NV to help manufacture a vaccine that uses a different technology called messenger RNA.

GSK is also helping manufacture doses of a vaccine by U.S. company Novavax Inc. that is in the final stage of testing.

Additionally, GSK is collaborating with Canada's Medicago Inc., a biotech firm partly owned by Marlboro cigarette maker Philip Morris International Inc., on a plant-derived Covid-19 vaccine that is in late-stage trials.

Write to Jenny Strasburg at


(END) Dow Jones Newswires

May 17, 2021 08:16 ET (12:16 GMT)

Copyright (c) 2021 Dow Jones & Company, Inc.
Sanofi (EU:SAN)
Historical Stock Chart
From Jun 2021 to Jul 2021 Click Here for more Sanofi Charts.
Sanofi (EU:SAN)
Historical Stock Chart
From Jul 2020 to Jul 2021 Click Here for more Sanofi Charts.