GlaxoSmithKline (GSK) and Medicago have reported that interim data from the Phase II part of Phase II/III clinical trial of the latter’s plant-derived Covid-19 vaccine candidate showed significant neutralising antibody responses.

The vaccine candidate was evaluated in combination with GSK’s pandemic adjuvant. It led to tenfold neutralising antibody levels compared to those in people recovering from the disease.

The Phase II/III trial is being conducted to validate the selected formulation and dosing schedule of CoVLP.

It is analysing whether two doses of 3.75µg CoVLP plus GSK’s pandemic adjuvant administered 21 days apart demonstrate favourable immunogenicity and safety profile in healthy adults aged 18 to 64 and elderly subjects aged 65 and above with comorbidities.

The randomised, observer-blind, placebo-controlled Phase II segment of the trial assessed the safety and immunogenicity of the adjuvanted vaccine candidate, with 306 participants in each age group at various sites in Canada and the US.

Trial results showed a tolerable safety profile with only mild or moderate adverse events observed.

Furthermore, two doses of the vaccine candidate stimulated a substantial humoral immune response in the two participating age groups.

Medicago Scientific and Medical Affairs executive vice-president Nathalie Landry said: “After two doses, the adjuvanted vaccine candidate induced robust neutralising antibody and cellular immune responses in all subjects, irrespectively of age.

“These results give us confidence as we continue to move forward with our Phase III clinical trial. We hope to add another tool in the global fight against Covid-19, particularly as cross-protection emerges as an important consideration in vaccination efforts worldwide.”

The Phase III part of the trial, which commenced in March this year, is enrolling subjects at sites in the US, the UK, Canada and Brazil, with more sites to be launched soon.

The event-driven, randomised, observer-blinded, crossover placebo-controlled Phase III segment will analyse the efficacy and safety of the CoVLP formulation versus placebo in up to 30,000 participants.

These results come a day after Sanofi and GSK reported strong immune responses with their adjuvanted recombinant Covid-19 vaccine candidate in Phase II clinical trial.