Vaxart announces publication of norovirus vaccine candidate data

Vaxart (VXRT) announced the publication of complete data from a Phase 2b challenge study of its first-generation oral pill norovirus vaccine candidate in Science Translational Medicine. Consistent with preliminary data reported in September 2023, the complete results show that the trial met five of its six primary endpoints and demonstrate the safety, efficacy, and immunogenicity of the vaccine candidate. Additional data included in the current publication include results from machine learning analyses that identify functional blocking antibody and fecal IgA as robust correlates of protection. These additional results will help inform the development of the Company’s second-generation oral pill norovirus vaccine candidate. Vaxart initiated a Phase 1 trial comparing its first- and second-generation norovirus vaccine candidates in March 2025. The vaccine was immunogenic and protected against norovirus infection, with a 30% relative reduction for the vaccine group compared with placebo. The vaccine group had a lower incidence of norovirus gastroenteritis (21% relative reduction), but was not statistically different. The vaccine significantly increased serum IgA, IgG, norovirus-blocking antibodies, and antibody-secreting cells. The vaccine stimulated mucosal-homing B cells and significantly increased norovirus-specific antibodies in saliva, nasal lining fluid and intestine. Most common solicited symptoms reported in the week following vaccine administration; headache and malaise/fatigue were reported at similar rates in the placebo group. A totality of evidence approach of the primary endpoint data was used to consider the probability of multiple simultaneous positive outcomes, and the outcome indicated an overall beneficial effect of the vaccine candidate. Participants in the vaccine cohort had reduced frequency of emesis and reduced viral load in emesis and stool samples. The vaccine was safe and well-tolerated after norovirus challenge, with no vaccine-related serious events or dose-limiting toxicities reported. Most adverse events were mild, with few moderate and no severe AEs reported. Machine learning analyses identified norovirus VP1-specific fecal IgA and serum norovirus blocking antibodies as robust and statistically significant CoP against norovirus infection.