GlaxoSmithKline (GSK) and Medicago have started phase 3 clinical testing of their plant-based adjuvanted COVID-19 vaccine.
The phase 3 study will evaluate two 3.75 micrograms doses of the vaccine candidate, administered 21 days apart.
Initially, it will enrol up to 30,000 participants including healthy adults aged 18 to 65 years old, after which older adults aged 65 years and up and adults with comorbidities will also be included.
In a statement, Medicago said it had received approval from Canadian and US regulatory authorities to proceed with enrolment in the late-stage study based on positive interim phase 2 results.
The phase 2 portion of the clinical development programme is almost completed, with results expected to be made public next month, according to GSK and Medicago.
The vaccine candidate combines Medicago’s recombinant coronavirus virus-like particles (CoVLP) with GSK’s pandemic adjuvant system.
Medicago’s CoVLPs mimic the structure of the SARS-CoV-2 virus that causes COVID-19, which allows them to be recognised and targeted by the immune system.
In addition, adjuvants can be of particular use in a pandemic situation, as the boosted immune response can reduce the amount of antigen required per dose, allowing for more vaccine doses to be manufactured and distributed.
“This advance to late stage clinical testing further reinforces our confidence in the adjuvanted vaccine candidate’s potential to make a difference in the continued fight against COVID-19. We look forward to sharing results later this year,” said Thomas Breuer, chief medical officer, GSK Vaccines.
GSK and Medicago signed a deal in July 2020 to develop and evaluate a COVID-19 vaccine candidate combining Medicago’s CoVLPs and GSK’s adjuvant.
In an early study of the vaccine, Medicago said that all subjects who had been given the experimental vaccine developed “a promising antibody response after two doses”.
The US Food and Drug Administration (FDA) granted GSK and Medicago’s adjuvanted vaccine candidate a fast track designation last month.
“The FDA’s decision to grant fast track designation for Medicago’s vaccine candidate will help us expedite our efforts to bring the first plant-derived COVID-19 vaccine to market, subject to regulatory approval,” said Carolyn Finkle, chief operating officer of Medicago.
“We are grateful to the FDA and look forward to continuing to work with them as we move forward in our clinical trials, planned application for emergency use authorisation and eventual vaccine licensure application process,” she added.