Vaxart, Inc. announced positive Topline data from the dose-ranging Phase 2 clinical trial of its oral pill bivalent norovirus vaccine candidate. Preliminary results of the trial (NCT05626803) showed robust serum immune responses across all doses at Day 29 relative to Day 1. Both doses showed a similar increase in serum antibody responses with no statistical difference between the medium and high dose arms. At Day 29, increases in serum IgA, IgG, and BT50, for both the GII.4 and GI.1 strains in the vaccine arms, were similar to those seen in previous norovirus studies conducted by Vaxart. Mucosal and cell-based assay data will be available at a later date.

Results from this Phase 2 dose-ranging study also demonstrated that the bivalent norovirus vaccine candidate was well tolerated, with a favorable safety profile that included no vaccine-related serious adverse events (SAEs) and no dose limiting toxicity. Adverse event rates for both doses were similar to placebo. The study enrolled 135 healthy adults at three sites in the United States.

The first 10 subjects received open label high-dose vaccine and the remaining subjects were randomized to high- or medium-dose vaccine (N=50 for each arm) or placebo (N=25). This is the seventh clinical trial completed in Vaxart’s norovirus program, and it supports previous findings of robust immunogenicity and benign tolerability. Collectively, the data from these completed trials have shown immune responses from Vaxart’s oral norovirus vaccine constructs to be strong, long-lasting, and comparable to natural infection.

Final results could vary slightly from these preliminary data, and additional timepoint measures and mucosal data from this study are expected in the second half of 2023. Vaxart’s Norovirus Program Next Steps: The data reported support the continued development of Vaxart’s oral norovirus vaccine candidate in adult populations and add to the growing body of evidence supporting its clinical utility. These data, along with upcoming topline data from the ongoing Phase 2 G1.1 challenge study, will inform dosage amounts for a bivalent norovirus Phase 2b study, the next step in progressing the vaccine candidate.

The Phase 2b study is expected to add safety data that, if successful, will then enable Vaxart to schedule an End-of-Phase 2 meeting with the U.S. Food and Drug Administration (the “FDA”), potentially in 2024. Data from the Phase 2 study announced on July 6, 2023, along with a future Phase 3 study, are required for a Biologics License Applications submission to the FDA as the Company pursues a commercial pathway for its bivalent norovirus candidate.