On May 18, 2021, GlaxoSmithKline and Medicago reported positive interim Phase 2 clinical trial safety and immunogenicity data for Medicago’s plant-derived COVID-19 vaccine candidate, which has been tested in combination with GSK’s pandemic adjuvant.

These results are part of the ongoing Phase 2/3 study and reiterate the promising profile observed during Phase 1 testing. Immunogenicity, as measured by the neutralising antibody titer, was high: about 10 times higher than those in a panel of sera from patients recovering from COVID-19. No related severe adverse events were reported and reactogenicity was generally mild to moderate and short in duration.

The Phase 3 trial of the vaccine candidate launched on 16 March 2021. Trial sites are currently enrolling subjects in Canada, the United States, the United Kingdom and Brazil, with additional sites expected to be added in the coming weeks. The vaccine candidate has received Fast Track designation by the FDA in the United States, and Health Canada has initiated a review of Medicago’s COVID-19 rolling submission under the Interim Order.

The Phase 2/3 study is a multi-portion design to confirm that the chosen formulation and dosing regimen of CoVLP (two doses of 3.75 µg CoVLP combined with GSK’s pandemic adjuvant given 21 days apart) has an acceptable immunogenicity and safety profile in healthy adults 18-64 years of age, elderly subjects aged 65 and over and adults with comorbidities.

The Phase 2 portion of the trial was a randomized, observer-blind, placebo-controlled study to evaluate the safety and immunogenicity of the adjuvanted recombinant COVID-19 plant-derived vaccine candidate in subjects aged 18 and above. It was conducted in multiples sites in Canada and the United States in a population composed of healthy adults (18-64y), elderly adults (over 65y) and adults with comorbidities. Each age group enrolled up to 306 subjects randomized 5:1 to receive the adjuvanted CoVLP vaccine candidate: placebo and with 2:1 stratification in older adults (65-74 and ≥75). All subjects will be followed for a period of 12 months after the last vaccination for the assessment of safety and durability of the immune responses to the vaccine candidate which will be the final analysis.

The Phase 3 portion is an event-driven, randomized, observer-blinded, crossover placebo-controlled design that will evaluate the efficacy and safety of the CoVLP formulation, compared to placebo, in up to 30,000 subjects in North America, Latin America and Europe and within the same population.

GSK is collaborating with several organisations on COVID-19 vaccines by providing access to our adjuvant technology. In addition to our work with Medicago, we recently announced positive Phase 2 data from our collaboration with Sanofi to develop an adjuvanted, protein-based vaccine candidate and expect to begin a Phase 3 trial in Q2. An earlier stage collaboration with SK Bioscience is also ongoing. SK Bioscience receives funding from CEPI and the Bill and Melinda Gates Foundation to develop differentiated, affordable COVID-19 vaccines for supply globally through the COVAX facility. The use of an adjuvant can be of particular importance in a pandemic since it may reduce the amount of vaccine protein required per dose, allowing more vaccine doses to be produced and contributing to protecting more people. Based on experience with other adjuvanted vaccines, there is potential for increased cross protection against COVID-19 variants which will be further studied.