Clinical-stage biotech company Vaxart announced Thursday that a second dose of its oral norovirus vaccine boosted immunity in clinical trial participants who had previously received the vaccine more than a year prior.
Rafael Henrique/SOPA Images/LightRocket via Getty Images
Clinical-stage biotech company Vaxart announced Thursday that a second dose of its oral norovirus vaccine boosted immunity in clinical trial participants who had previously received the vaccine more than a year prior. The company hopes these findings will have positive implications for its COVID-19 oral vaccine program, which is also currently under development.
The announcement was based on data from the company’s Phase Ib study, which assessed the ability of its oral norovirus vaccine to boost immunogenicity in 12 participants. Some of these participants had initially received the oral vaccine in late 2019 and subsequently received the vaccine again in early 2021.
A total of seven study participants who were previously immunized with Vaxart’s oral vaccine demonstrated similar immune responses to norovirus as the five participants who had not been previously immunized with the oral vaccine in 2019. In both previously vaccinated and unvaccinated individuals, the researchers observed similar increases in antibody blocking titer 50, a surrogate neutralizing antibody measurement in serum.
Additionally, the investigators found no difference between participants who had previously received versus those who had not previously received the oral vaccine in terms of antibody-secreting B cell (ASC) responses to norovirus VP1, as measured seven days after the boost.
Also, there was a significant increase in serum immunoglobulin (Ig) G and IgA antibody responses at 29 days following boost immunization. No differences in titer were observed in participants who had received a prior oral norovirus vaccine versus participants who hadn’t received the vaccine.
“These results are very important because they support our belief that our oral tablet vaccines have the potential to be used repeatedly for indications that may require an annual boost, such as flu, COVID-19, or norovirus,” according to a statement made by Andrei Floroiu, chief executive officer of Vaxart. “We are excited by these findings and by the implications for all of our vaccines.”
Vaxart’s founder and chief scientific officer, Dr. Sean Tucker, added the results could hold implications for the company’s other vaccines in development, including its oral COVID-19 vaccine table, given all vaccine candidates are based on the same platform and rely on the same vector.
“Moreover, this clinical evidence has the potential to differentiate our vaccines from injectable vector-based vaccines,” said Dr. Tucker. “Typically, when you inject viral vector-based vaccines, they generate immune responses against the viral vector as well as the intended antigens.”
Dr. Tucker noted that “anti-vector antibodies from the injected vaccine immune response may prevent the viral vector from serving as a boosting agent,” but the company’s “norovirus trial results suggest that Vaxart’s vaccines may not be hampered by certain antibody response challenges that can occur with injectable viral vector-based vaccines.”
In May, Vaxart showed in a Phase I study that its oral COVID-19 vaccine candidate VXA-CoV2-1 triggered mucosal immunity, indicating it had broad cross-reactivity against other coronaviruses. “Our vaccine’s immune response appears very different than that seen from the leading injectables: mucosal antibodies rather than serum antibodies, and more potent T-cell responses,” said Floroiu, in a statement on the findings. “For our first oral COVID-19 vaccine candidate, we believe that these differences in immunogenicity profile may have a benefit in cross-reactive protection.”
Several other companies are currently on the hunt for an effective oral COVID-19 vaccine, including Israel-based startup company MigVax. In June, the company announced its subunit oral vaccine MigVax-101 demonstrated efficacy as a booster for previously vaccinated individuals.
In addition, Oravax Medical, formed in a joint venture by Premas Biotech and Oramed, is also racing to develop an oral COVID-19 vaccine. A pilot animal study showed its current vaccine candidate induced systemic immunity through IgG and IgA. Oravax plans to initiate a clinical trial during the second quarter of this year.
