Phase 1 randomized, observer-blinded, placebo-controlled study of a SARS-CoV-2 mRNA vaccine PTX-COVID19-B

Pillar 4
Functional Genomics & Structure-Function of VOCs

This article describes the results of the first human clinical trial for a COVID19 mRNA-based vaccine, called PTX-COVID19-B, conducted in Canada in 2021. This vaccine was made in Canada by Providence Therapeutics Holding, Inc, a private company that received some support from the Canadian Government for development of the vaccine. The trial evaluated safety, tolerability and immune responses in healthy seronegative adults aged 18 to 64. Three dose-groups, 16 ug, 40 ug, 100 ug, and placebo controls were evaluated after administration of the vaccine on day 1 and day 28. All participants were randomly placed in the different dose groups and were monitored by a blinded observer. Local and systemic reactions were monitored during and after vaccination for up to day 42 (two weeks post second vaccination). Antibody titers, both biding and neutralizing, and T cell reactivity against spike, were evaluated to determine vaccine capacity to induce a strong immune response against SARS-CoV-2.

After the first and second dose of vaccine, systemic and local reactions were absent or mild in most subjects. The most common local and systemic adverse events found in all subjects were pain at the injection site and headache, respectively.

After the first immunization, all subjects seroconverted, producing high titers of anti-receptor-binding-domain, anti-spike, and neutralizing antibodies, including neutralizing antibodies against the ancestral viral strain and the Alpha, Beta, and Delta variants of concern. The immune response was dose-dependent and increased over 10- 20 times after the second dose. All tested doses of PTX-COVID19-B were safe, well-tolerated, and provided a strong immunogenicity response. The 40-mg dose showed fewer adverse reactions than the 100-mg dose, supporting further investigation of the 40-mg dose. Currently PTX-COVID19-B has been evaluated in a Phase 2 trial and is being considered for a Phase 3 booster trial.

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