GlaxoSmithKline (GSK) and Medicago announced that Medicago’s plant-based Covid-19 vaccine, together with GSK’s pandemic adjuvant, has shown positive efficacy and safety results in a Phase 3 study.

The late-stage clinical trial was conducted in more than 24,000 participants, aged 18 years and above, across six countries, said the two companies.

In the Phase 3 study, the vaccine demonstrated an overall efficacy of 71% against all variants of SARS-COV-2, and 75.6% in people who were not exposed to Covid-19.

The vaccine candidate showed 75.3% efficacy against the Delta variant, which was dominant worldwide, and was 88.6% effective against the Gamma variant.

Omicron variant was not included in the study, as it was not circulating during the study period, said both companies.

Canada-based Medicago intends to use the positive study results to seek Health Canada approval for the vaccine candidate, as part of its rolling submission.

Medicago CEO and president Takashi Nagao said: “This is an incredible moment for Medicago and for novel vaccine platforms. The results of our clinical trials show the power of plant-based vaccine manufacturing technology.

“If approved, we will be contributing to the world’s fight against the Covid-19 pandemic with the world’s first plant-based vaccine for use in humans.

Medicago chief scientific officer Yosuke Kimura said: “I am pleased to see our vaccine candidate moving forward and bringing to the world the first plant-based vaccine against Covid-19, diversifying the pool of vaccines available to help improve public health and protect more people.”

Medicago is a biopharmaceutical company focused on discovering, developing, and marketing plant-based virus-like particles (VLP) for protein vaccines and medications.

VLPs work by imitating the native structure of viruses, to make them easily recognised by the immune system. They are non-infectious, as they lack the genetic material to replicate.

Medicago has initiated regulatory filing for its vaccine candidate with the US FDA and the UK’s MHRA, and started a Phase 1/2 trial in Japan, to seek regulatory approval.

GSK global Covid-19 adjuvanted vaccines lead and chief global health officer Thomas Breuer said: “These are encouraging results given data were obtained in an environment with no ancestral virus circulating.

The global Covid-19 pandemic is continuing to show new facets with the current dominance of the Delta variant, upcoming Omicron, and other variants likely to follow.

“The combination of GSK’s established pandemic adjuvant with Medicago’s plant-based vaccine technology has significant potential to be an effective, refrigerator-stable option to help protect people against SARS-CoV-2.”

In a separate development, GSK-Vir’s investigational Covid-19 therapy sotrovimab has shown activity against the new Omicron variant, according to preclinical data on bioRxiv.

The preclinical data was collected from pseudo-virus testing of the combination of all known mutations of the Omicron variant spike protein, said the company.