Feb. 22 (UPI) -- Pharma companies GlaxoSmithKline and Sanofi announced Monday that they have begun a second-stage clinical trial for their protein-based COVID-19 vaccine, after testing was delayed in December.
The drugmakers said more than 700 volunteers are involved in the Stage 2 testing for its protein-based adjuvanted coronavirus vaccine.
GSK and Sanofi delayed trials in December after finding that the vaccine wasn't promoting enough of an immune response in older people. Monday's announcement said developers improved the vaccine formulation and the new testing phase includes older adults.
The companies said the new phase will assess the potential for three antigen doses in volunteers in the United States, Panama and Honduras.
If results are positive, the companies expect to begin the Phase 3 study between April and July. If that final stage is successful, they expect to make the vaccine available sometime between October and January.
"We are confident our vaccine candidate has strong potential and we are very encouraged by the latest preclinical data," Sanofi Executive Vice President Thomas Triomphe said in a statement.
"This new Phase 2 study will enable us to identify the final vaccine formulation for adults of all ages."
The vaccine in development at GSK and Sanofi is different than those produced by Pfizer and Moderna (mRNA) and Johnson & Johnson (adenovirus), in that it's considered more experimental and uses a protein adjuvant intended to promote a stronger immune response against the coronavirus.
"The world needs multiple vaccines and we are confident that combining our proven pandemic adjuvant system with this improved antigen formulation will have significant potential as the pandemic evolves," GSK Vaccines President Roger Connor noted.
Sanofi also said Monday that it will aid Johnson & Johnson in formulating and filling 12 million doses of its one-shot vaccine per month when it's approved.
Sanofi is also developing an mRNA vaccine with Translate Bio and says it has seen "encouraging preclinical data." An early-phase study is planned for this spring.