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TORONTO – The Canadian company behind a new plant-based COVID-19 vaccine candidate released the results of their Phase 1 clinical trials, stating that two doses of their adjuvanted vaccine stimulated a significant antibody response in 100% of the study subjects .
“They are even better than we had hoped for,” said Nathalie Landry, Medicago’s executive vice president of scientific and medical affairs.
“When we talk about neutralizing antibody responses, we say it is quite remarkable, especially when we compare it with a subject who has recovered from the disease.”
Those who received the Medicago adjuvanted vaccine in the phase 1 study actually had higher antibody levels than the levels found in those who had COVID-19, Landry told CTVNews.ca in a telephone interview.
Medicago, a Quebec-based company, launched the first human trials in July.
In phase 1, they looked at around 180 healthy subjects between the ages of 18 and 55. Participants were given the vaccine alone or the vaccine with one of two mixed adjuvants: GlaxoSmithKline pandemic adjuvant (GSK) or Dynavax CpG 1018 adjuvant.
An adjuvant is a substance that is added to vaccines to enhance their effects and allow for a higher immune response. They can be made from a variety of materials, including plants, aluminum and squalene oil, which are largely derived from sharks. The researchers wanted to measure what difference adding each adjuvant would make for the immune response.
They found that the vaccine candidate alone produced antibodies in the subjects, but required a much higher dosage level to get adequate results.
It was the adjuvanted vaccines that really had an effect.
After two doses of adjuvanted vaccine, regardless of the adjuvant used, the antibody response increased significantly. However, subjects developed anti-spike IgG antibodies after a single dose of the vaccine when mixed with the GSK adjuvant, according to the news release.
“[GSK’s was] the adjuvant that gave us the best immune response a [a] very low dose, “Landry said.
He explained that although they tested three doses at 3.75, 7.5 and 15 micrograms, the antibody response did not increase with increasing dosage.
“We only need 3.75 micrograms to achieve a very significant level of cellular and antibody immune responses,” he said.
Being able to stimulate an immune response at a lower dose means they would be able to produce more vaccine if it clears the rest of the steps.
In October, the company announced that it reached an agreement with the federal government to provide Canada with up to 76 million doses of their vaccine, subject to approval by Health Canada.
The success of the GSK adjuvant means that, going forward, Medicago will only use their vaccine candidate mixed with GSK’s pandemic adjuvant in further studies.
This phase also demonstrated the safety of the vaccine candidate for further studies, as no subjects experienced any serious adverse side effects, only mild and short-lived side effects, according to the release.
HOW PLANTS PARTICIPATE IN THE DEVELOPMENT OF VACCINES
Medicago’s vaccine candidate differs from many others currently in human trials in that it uses “coronavirus virus-like particles” (CoVLP), which mimic the virus to stimulate an immune response without introducing any form of the actual virus into the body. human.
“Generally, when developing a vaccine for COVID, you’re looking for two things,” Landry said. “You’re looking for neutralizing antibody responses and cellular immune responses.”
Their adjuvanted vaccine can trigger both of these, he said.
To make the vaccine, Medicago uses plants as, essentially, living factories to produce the antigen in the vaccine that stimulates an immune response. This is achieved through recombinant technology: the genetic code is transferred to a plant, at which point “the plant will start expressing that antigen as its own,” according to Landry.
The plant they use is called nicotiana benthamiana, a relative of the tobacco plants, which grows quickly and can “produce a huge amount of protein,” he said, making it a favored host for biopharmaceuticals.
“This is 20 years of development, which is the basis for this innovative manufacturing technology,” Landry said. “And that’s something that was developed in Canada.”
NEXT STEPS
In Phase 2 they will study more subjects, in addition to those of other age groups not included in the first trial. It will involve about 600 subjects, aged between 18 and 64 years.
“We also evaluate older people, make sure we’ve actually taken the right dose, and have a group safety and immunogenicity profile,” Landry said.
In the final phase of clinical trials, Medicago hopes to enroll approximately 30,000 subjects in different regions of the world.
“The reason we need to go global is that to prove the vaccine’s effectiveness, you have to go to the regions where the virus is circulating,” he explained.
He said they are on track with their evidence so far in terms of the timeline. Medicago aims to launch Phase 2 soon, pending approval. According to Landry, we got to hear the first results of that clinical trial in early 2021, around the same time they aim to launch Phase 3 of the trials.
Phase 3 is when the vaccine’s effectiveness is really tested, he said, so while the Phase 1 results are promising and support further evidence, they still don’t know if the vaccine will actively prevent transmission of the virus.
“But that’s the idea,” he said. “You have a high level of antibodies that can neutralize the virus, so you will prevent infection and hopefully also transmission of the virus.”
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