Sanofi’s, GSK’s COVID-19 Vaccine Sees Significant Delays in Move to Phase 2

Sanofi and GlaxoSmithKline (GSK) have decided to push back the phase 2b trial of their adjuvanted COVID-19 vaccine after finding it produced only a weak immune response in older patients, delaying the potential delivery of a vaccine that could contribute to the mass vaccination effort in the U.S.

The companies announced the delay Friday, disclosing that although interim results from its 441-participant phase 1/2 study showed the vaccine elicited an immune response comparable to recovered patients in participants aged 18 to 49, adults aged 50 and older displayed a low immune response — dashing hopes of moving on to a phase 2 study soon.

The weak reaction in the higher-risk population was “likely due to an insufficient concentration of the antigen,” the companies said, and they have now pushed back their phase 2b trial until February 2021. The study will use an improved formulation that hopefully produces better results in older participants.

The delayed phase 2b trial will receive support from HHS’ Biomedical Advanced Research and Development Authority under Operation Warp Speed (OWS), and the companies anticipate the vaccine becoming available in the fourth quarter of 2021 at the earliest.

The delay means that emergency clearance of AstraZeneca (AZ)’s and Johnson & Johnson’s COVID-19 vaccines, which are still in development but should have phase 3 trial results ready in late January or February, will be critical in ensuring there’s enough vaccine doses in the U.S. to vaccinate on demand.

OWS Chief Adviser Moncef Slaoui explained during a health summit last week that the two nonreplicating viral-vector vaccines are easier to scale up than Pfizer’s and Moderna’s mRNA-based vaccines and said there are plans to produce massive quantities of them on a monthly basis early next year.

“As of the month of February or March, we will be producing, between [AstraZeneca and Johnson & Johnson], between 150 [million] and 200 million doses per month,” he said, noting that J&J’s vaccine uses only a single shot.

Despite setbacks and questions that must be answered for AZ’s COVID-19 vaccine, Slaoui said that he believes there will be enough supplies of vaccines to vaccinate the entire country before the second half of 2021.

“If I look at this from a global basis … I think already with [our vaccine portfolio], I feel confident we can cover the U.S. population within the first half of 2021,” he said. — James Miessler