Investigational COVID-19 vaccine tablet safely induces immune response in Phase I

05 February 2021

Hannah Balfour / European Pharmaceutical Review

A preliminary analysis shows VXA-CoV2-1 was well-tolerated and induced T-cell and IgA responses against SARS-CoV-2 antigens in 35 patients.

Preliminary data shows VXA-CoV2-1, an oral COVID-19 tablet vaccine candidate, was generally well-tolerated and induced an immune response to SARS-CoV-2 antigens in a Phase I study.

“Our Phase I results highlight the importance of our differentiated vaccine design, as they suggest VXA-CoV2-1 could have broad activity against existing and future coronavirus strains. These results are timely, as we are seeing the emergence of new variants less responsive to first generation vaccines, thus making potential cross-reactivity another important advantage of next-generation vaccines,” said Andrei Floroiu, Chief Executive Officer of Vaxart Inc. – the company developing VXA-CoV2-1.

The VXA-CoV2-1 candidate contains two different SARS-CoV-2 proteins, Spike (S) and Nucleoprotein (N), a design which the company hopes will protect against both the prevalent and emerging strains. Virtually all other COVID-19 vaccines include just the S protein.

The Phase I study (NCT04563702) was designed to evaluate the safety and immunogenicity of VXA-CoV2-1 vaccine with multiple dosing schedules. Subjects were divided into three cohorts: the first cohort (5 subjects) received two low doses of vaccine 29 days apart, the other two (15 subjects each) received a single low or high dose of the vaccine. Safety and tolerability were monitored following vaccination as well as signs of immunogenicity, including general and SARs-CoV-2 specific immune responses.

The preliminary data shows that the vaccine tablet was well-tolerated, with no serious adverse events reported and the majority of other adverse events being mild.

In addition, the data suggests VXA-CoV2-1 triggered multiple immune responses against SARS-CoV-2 antigens, including:

  • CD8+ cytotoxic T-cell response to the S protein, necessary for long-lasting cross-reactive immunity
  • An increase in plasmablast cell number and an upregulation of the mucosal homing receptor, indicating activation of B cells that will home to the mucosa
  • An increase in proinflammatory Th1 cytokines, responsible for orchestrating the immune response to viral infection
  • IgA responses in serum and/or nasal swab samples in 100 percent of 2 dose subjects; neither neutralising antibodies nor IgG responses were detected in most subjects.

“We previously showed that our oral tablet vaccine technology worked to protect against flu – another airborne virus – as well as the leading injectable… With COVID-19, we have now seen that many vaccine approaches— mRNA, protein and viral vector, including three adenovirus vaccines – are protective, and that all available positive COVID-19 hamster challenge studies such as ours have translated into protection against COVID-19 in human trials,” Floroiu said.

The company said it expects to broaden its COVID-19 vaccine development plans, potentially with Phase II trials in COVID-19 naïve subjects to assess the efficacy of VXA-CoV2-1, or to evaluate the vaccine in previously vaccinated or exposed subjects, where a single dose boosting protocol could broaden and strengthen immune responses.

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