Plant-based COVID-19 vaccine candidate reports positive Phase 3 results

By Rachel Arthur

- Last updated on GMT

Plant-based COVID-19 vaccine reports positive Phase 3 results

Related tags plant-based vaccine efficacy Vaccines COVID-19 vaccine COVID-19 variants

Medicago and GSK’s plant-based COVID-19 vaccine candidate has reported an overall efficacy rate of 71% in Phase 3 trials: with the final regulatory submission for the vaccine to be filed with Health Canada shortly.

Headquartered in Quebec city, Medicago has developed the plant-based vaccine in combination with GSK’s pandemic adjuvant. Its technology has been in development for 20 years: primarily targeting an influenza vaccine but pivoting to COVID-19 in February 2020. The company’s tech uses plants to produce the Virus-Like Particles (VLPs) used in the protein vaccine.

Today Medicago released the results of its Phase 3 trial conducted in 24,000 subjects across six countries: reporting that the trial met primary and secondary endpoints for which data are available.

The overall vaccine efficacy rate against all variants of SARS-COV-2 was 71%; while the candidate demonstrated efficacy of 75.3% against COVID-19 of any severity for the globally-dominant Delta variant. The Omicron variant was not circulating during the study.

Medicago notes the efficacy rates are not comparable to figures for authorized vaccines as those were based on the ancestral virus strain rather than variants. 

The vaccine has been tested with adults aged 18+, elderly subjects aged 65+, and adults with comorbidities. Full results of the Phase 3 study are to be published in a peer-reviewed publication as soon as possible.

“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,”​ said Takashi Nagao, CEO and President at Medicago. “I want to thank everyone who participated in our clinical trials, our collaborators at clinical trial sites, our partners at GSK, the Government of Canada and Government of Quebec, Mitsubishi Tanabe Pharma Corporation, and all of our employees and our shareholders, for their commitment to advancing vaccine science when the world needs it.”

The vaccination regimen calls for two doses (3.75 microgram of antigen in combination with GSK’s pandemic adjuvant) given intramuscularly 21 days apart. The vaccine is stored at 2 °C to 8 °C, enabling the use of traditional vaccine supply and cold chain channels.

Regulatory process under way with Health Canada, FDA and MHRA

Medicago started a rolling review for the candidate in April with Health Canada and will now seek regulatory approval ‘imminently’.

It has also initiated the regulatory filing process for the vaccine with the US FDA and UK MHRA; while preliminary discussions are underway with the WHO in preparation of a submission to the organization.

Medicago has also initiated Phase 1/2 trial in Japan where it plans to submit for regulatory approval in combination with the Phase 2/3 global study results next spring.

Plants as 'mini protein factories'

Founded in 1999, Quebec City’s Medicago is a pioneer of plant-derived therapeutics.

Its tech takes the idea of traditional vaccine manufacturing – based on using eggs to produce viruses – and instead uses living plants as the bioreactor that produces a protein particle that mimics the target virus.

The first step is to create the required protein particle and introduce it into a plant-specific bacterial vector. This is then taken up by plants which multiplies the vector. It takes just four to six days for the ‘mini-factories’ to produce the Virus-Like-Particles (VLPs) – compared to around six months for egg-based production (The company highlights that plants are not genetically modified; rather, the plants’ natural cellular processes are used).

While initial experiments had used alfalfa (Medicago is the Latin word for alfalfa), today the company uses N. benthamiana​​ plants: a relative of tobacco which has a weakened immune system meaning genetic material can be hosted rather than rejected by the plant.

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