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US-based Vaxart has announced positive topline data in a Phase II trial of its norovirus vaccine candidate.

Preliminary results of the Phase II trial (NCT05626803) of the oral pill bivalent showed robust immune responses across all doses at day 29. Both doses showed a similar increase in antibody responses with no statistical difference between the arms.

Increased serum IgA, IgG, and BT50 levels for both the GII.4 and GI.1 strains in the vaccine arms were comparable to those observed in previous norovirus studies conducted by Vaxart.

Results also showed that the oral bivalent vaccine candidate was well tolerated, with a favourable safety profile and no vaccine-related adverse events. 

GlobalData predicts a global sales forecast for Vaxart’s bivalent of $271m in 2029. GlobalData is the parent company of the Clinical Trial Arena.

How the trial was conducted

The study enrolled 135 healthy adults at three sites in the US. It was a multicentre, randomised, double-blind, placebo-controlled, single-dose, dose-ranging study to determine the safety and immunogenicity of the oral pill bivalent.

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By GlobalData

Vaxart’s chief medical officer Dr James Cummings said: “Topline data reported further validate the potential of our norovirus vaccine candidate and, more broadly, our oral vaccine platform. These data, additional forthcoming data from this study, and the data we expect from our norovirus challenge study will help inform our selection of dosage levels in a larger Phase IIb study and support an end-of-Phase II meeting with the US Food and Drug Administration.”

The vaccine candidate elicits therapeutic activity by stimulating the immune system against disease antigens. The adenovirus delivers the genes for the specific viral antigens. These antigens, once expressed, induce T-cell immune responses.

Next steps

These data and upcoming topline data from an ongoing Phase II challenge study will inform dosage amounts for a bivalent norovirus Phase IIb study. The Phase IIb study is expected to add safety data to enable Vaxart to schedule an end-of-Phase II meeting with the US Food and Drug Administration (FDA), potentially in 2024.

Norovirus is a contagious virus with symptoms of vomiting and diarrhoea. It is sometimes called “stomach flu”, however, norovirus illness is not related to the flu. It is the leading cause of acute viral gastroenteritis in all age groups in the US.

Vaxart vaccines are designed for administration as pills for storage and shipping without refrigeration and eliminate the risk of needle-stick injury. There are currently no approved vaccines for noroviruses.