Vaxart, Inc., a clinical-stage biotechnology company developing oral recombinant vaccines that are administered by tablet rather than by injection, today announced positive topline results from the randomized, double-blind, placebo-controlled Phase 1b safety, immunogenicity and interference study with its oral tableted bivalent norovirus vaccine in healthy adults. The study met all primary endpoints for safety and demonstrated robust immunogenicity, with 78% – 93% of subjects responding by eliciting IgA antibody secreting cells (ASC), a key marker for mucosal immunity and a potential correlate of protection for norovirus disease.


“Norovirus is a very contagious disease which can be especially harmful to children under age 5 as well as to older adults,” said William Schaffner, MD, medical director of the National Foundation for Infectious Diseases (NFID) and Professor of preventive medicine and infectious diseases at Vanderbilt University School of Medicine. “An effective and safe vaccine would be critical to protecting high-risk populations against serious illness caused by norovirus, especially if it could be administered orally.”

Oral Norovirus Vaccine: Vaxart announces positive pre-clinical data

“These results are in line with the robust immune response profile seen in previous studies with our noro-GI.1 tablet vaccine, while the immunogenicity of our new noro-GII.4 tablet vaccine trended even higher with an IgA ASC response rate of 90% or greater,” said Wouter Latour, M.D., chief executive officer of Vaxart. “Norovirus infection causes $60 billion in global healthcare-related costs annually, and there is no licensed vaccine available. We believe these favorable results put us on track to develop a vaccine with the potential to become the product of choice for policy makers and health care professionals in a $3+ billion market. We are now forging ahead with the Phase 2 dose confirmation study planned for 2020.”

Both the oral norovirus GI.1 and GII.4 vaccines were well tolerated, with no treatment-related serious adverse events reported. Most solicited and unsolicited adverse events were mild in severity and there were no significant differences observed between the vaccine and placebo treatment groups.

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Vaxart’s bivalent vaccine demonstrated robust immunogenicity, with an IgA ASC response rate of 78% for the GI.1 strain and 93% for the GII.4 strain for the bivalent cohort of the study, and 86% and 90%, respectively, for the two monovalent cohorts of the study. There was no interference observed in the bivalent arm of the study.

Oral norovirus vaccine to enter Phase 1b trial

The Phase 1b norovirus bivalent vaccine trial enrolled a total of 80 subjects. After enrollment of an open-label sentinel GII.4 group of 5 subjects, the remaining 75 subjects were randomized in a blinded manner to one of 4 treatment groups: 15 subjects in each monovalent group received an oral 5×1010 I.U. dose of either the norovirus GII.4 or GI.1 vaccine, 30 subjects in the bivalent group received a 5×1010 I.U. dose of both the norovirus GII.4 and GI.1 vaccine administered concurrently, and 15 subjects received placebo tablets. The trial was designed to evaluate safety, immunogenicity and interference of Vaxart’s oral bivalent norovirus vaccine by comparing the bivalent vaccine group to the two monovalent vaccine groups, as well as the placebo group.