Vaxart’s 2nd generation vaccine technology shows greater antibody response

Overview

• Vaxart, Inc, a clinical-stage biotechnology company developing a range of oral recombinant pill vaccines based on its proprietary delivery platform, reported positive topline results from the phase 1 clinical trial evaluating its second-generation oral pill norovirus vaccine constructs head-to-head against its first-generation constructs.
• Second-generation norovirus constructs produce statistically significant increases in GI.1 and GII.4 norovirus blocking antibodies (141% and 94%, respectively) compared with first-generation constructs, supporting potential for improved protection against infection.  
• Vaccine candidates were safe and well-tolerated across all dose groups with no vaccine-related serious adverse events reported. 

All the process in Phase 1 trial

• The open-label, phase 1 trial was conducted in 60 healthy volunteers who were randomized to receive the first-generation constructs, an equivalent dose of the second-generation GI.1 and GII.4 constructs, or a lower dose of the second-generation constructs (n=20 for each group). 
• The primary immunological endpoint was norovirus blocking antibody assay (NBAA) titer at day 0 and day 28. 
• In a phase 2 challenge trial of the first-generation vaccine constructs, these functional NBAA titers correlated with protection against norovirus infection. 
• Although the study was not powered to determine superiority by statistical methods, the increase in NBAA titers with the second-generation constructs was sufficiently large (141% for the GI.1 construct and 94% for the GII.4 construct) to demonstrate statistical significance at the higher dose.

Words from the CSO, Sean Tucker:  Vaxart

• Consistent with what we previously demonstrated in animal models, these clinical data prove that our second-generation constructs increased antibody titers in humans, providing additional compelling evidence of the potential of our oral pill vaccine candidates,” said Sean Tucker, Vaxart’s founder and chief scientific officer. 
• We previously demonstrated that our first-generation construct for the norovirus GI.1 genotype protected against infection and that protection correlated with increased antibody levels detected by our proprietary NBAA assay. The significant increases in NBAA titers reported today give us high confidence that our second-generation constructs will provide even greater protection against infection.”

Key findings of the study

• Significantly increased GI.1 NBAA titers in the cohort receiving the high dose of the second-generation constructs compared with an equivalent dose of the first-generation constructs. 
• A 141% increase in GI.1 NBAA titers was observed, which corresponds to a 3.2 increase in Geometric Fold Response from 2.2 to 5.4.

CEO’s statement on this achievement

• We are very pleased with these results, which exceeded our expectations. With no currently approved vaccine, norovirus causes millions of infections globally resulting in billions of dollars of economic burden,” said Steven Lo, CEO of Vaxart. 
• We believe that our second-generation norovirus oral pill vaccine candidate has the potential to provide first-in-class or best-in-class protection against this highly contagious virus where there is significant unmet need. We intend to incorporate these compelling new data into our ongoing discussions with potential partners.”

Preparations for phase 2 studies

• Assuming a partnership or other funding, Vaxart expects to conduct a phase 2b safety and immunogenicity study that could potentially begin as early as the second half of 2025 followed by an end of phase 2 meeting with the US Food and Drug Administration. 
• A phase 3 clinical trial could then begin as early as 2026.

The oral pill technology by Vaxart

• Vaxart’s oral pill technology works by inducing expression of antigen proteins in the cells of humans’ intestines. 
• Vaxart’s second-generation technology was developed in 2023 and 2024 to achieve two purposes: first, to increase expression levels of the antigen proteins, and thus to greatly increase antibody titers; and second, to improve manufacturability. 
• In pre-clinical experiments, the second-generation constructs substantially improved antibody responses in animal models. 
• The trial reported today, for the updated norovirus vaccine candidate, is the first test in humans of the new technology. 
• Vaxart has also adopted the new technology in its latest Covid-19 vaccine candidate and implemented these improvements throughout its portfolio.

The norovirus

• There is no approved vaccine against norovirus, a leading cause of acute gastroenteritis (AGE) worldwide that is responsible for outbreaks of infection and illness globally. 
• Each year there are approximately 685 million norovirus infections globally, with 20 million infections occurring annually in the United States. 
• Due to these high rates of infection, norovirus is believed to cause nearly 20% of diarrheal disease globally.

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