Vaxart (United States)

Abstract Background Norovirus (NV) is a leading cause of acute gastroenteritis worldwide. Currently no specific therapy exists for norovirus gastroenteritis (NVG). VXA-G1.1-NN is a nonreplicating adenovirus-vectored thermostable oral NV vaccine shown in clinical trials to be safe, well-tolerated and generates robust serum and mucosal immune responses. This study investigated safety, immunogenicity, and protective efficacy of VXA-G1.1-NN following NV GI.1 challenge.Figure 1.Clinical outcomes (norovirus infection and norovirus gastroenteritis) after norovirus challenge 28 days post vaccination with VXA-G1.1-NN or placebo Methods 165 healthy adults ages 18-49 were randomized 1:1 to a single oral vaccination of VXA-GI.1-NN or placebo. At 28 days post-vaccination, 141 eligible subjects were challenged with 1x106 genomic copies NV GI.1 inoculum. Solicited symptoms of reactogenicity were recorded for 1 week after vaccination and unsolicited adverse events (AEs) through 28 days post challenge. NVG was assessed by incidence of acute gastroenteritis (AGE) with evidence of NV+ infection. NV shedding was evaluated by qPCR in stool and emesis. VP1-specific GI.1 IgA antibody secreting cells (ASC), serum IgA and IgG, and Norovirus Blocking Antibody Assay (NBAA) were assessed. Totality of evidence analysis was used to assess overall vaccine protective effect.Figure 2.Viral shedding in stool by qPCR through 7 days post challenge with GI.1 NN virus inoculum following vaccination with VXA-G1.1-NN or placebo Results VXA-G1.1-NN was safe and well tolerated.VXA-G1.1-NN induced strong serum and cellular immunogenicity with substantial increases in VP1 GI.1- specific ASC and serum antibodies. Serum functional antibody responses, determined by NBAA, were significantly higher in subjects in the vaccine group compared to placebo. VP1 specific IgA was significantly increased in nasal secretions and saliva in the vaccine group. Protective efficacy for prevention of NVG was 21% (p= 0.149) and for NV infection was 29% (p= 0.003). An 85% decrease in geometric mean viral shedding in stool in the VXA-G1.1-NN group was also observed. Totality of evidence analysis for all 6 outcomes simultaneously provided a z-score of 5.56 (p< 0.001), indicating protective benefit of VXA-G1.1-NN.Figure 3.Cellular and serum immune responses following vaccination with VXA-G1.1-NN or placebo Conclusion VXA-G1.1-NN was safe, immunogenic, and reduced both viral shedding and NV infection following NV challenge. VXA-G1.1-NN tableted vaccine may help limit outbreaks by reducing viral shedding. Totality of evidence analysis for treatment effect provided a strong statistical signal supporting a protective effect of VXA-G1.1-NN. Disclosures Susan Greco, MD, MPH, Vaxart, Inc: Stocks/Bonds (Public Company) Becca A. Flitter, PhD, MPH, Vaxart Inc: Stocks/Bonds (Public Company) Lam Nguyen, MD, CVS Health: Stocks/Bonds (Public Company)|Vaxart: Author is either employed and/or has received stock options from Vaxart as part of this work.|Vaxart: Stocks/Bonds (Public Company) Darreann Carmela Hailey, MS, Bionano Genomics: Stocks/Bonds (Public Company)|Vaxart, Inc.: Stocks/Bonds (Public Company) Sean N. Tucker, PhD, Vaxart, Inc.: Grant/Research Support|Vaxart, Inc.: patent|Vaxart, Inc.: Ownership Interest|Vaxart, Inc.: Stocks/Bonds (Public Company) James F. Cummings, MD, VAXART: Stocks/Bonds (Public Company)

SARS-CoV-2 variant clades continue to circumvent antibody responses elicited by vaccination or infection. Current parenteral vaccination strategies reduce illness and hospitalization, yet do not significantly protect against infection by the more recent variants. It is thought that mucosal vaccination strategies may better protect against infection by inducing immunity at the sites of infection, blocking viral transmission more effectively, and significantly inhibiting the evolution of new variants of concern (VOCs). In this study, we evaluated the immunogenicity and efficacy of a mucosally-delivered, non-replicating, adenovirus type 5-vectored vaccine that expresses the spike (S) gene of Wuhan (rAd5-S-Wuhan), delta (rAd5-S-delta), or omicron (rAd5-S-omicron) SARS-CoV-2 VOCs. Hamsters were immunized with these vaccines intranasally prior to challenge with omicron or delta variants. Additionally, one group was vaccinated by oral gavage with rAd5-S-Wuhan prior to challenge with the delta variant. Both intranasal and oral administration of rAd5-S-Wuhan generated cross-reactive serum IgG and mucosal IgA to all variant spike and RBD proteins tested. rAd5-S-omicron and rAd5-S-delta additionally elicited cross-reactive antibodies, though rAd5-S-omicron had significantly lower binding antibody levels except against its matched antigens. Two weeks after the final vaccination, hamsters were challenged with a SARS-CoV-2 variant; omicron or delta. Whether matched to the challenge or with rAd5-S-Wuhan, all vaccines protected hamsters from weight loss and lung pathology caused by challenge and significantly reduced viral shedding compared to placebo. Vaccination with rAd5-S-Wuhan provided significant protection, although there was an improved reduction in shedding and disease pathology in groups protected by the matched VOC vaccines. Nevertheless, Wuhan-based vaccination elicited the most cross-reactive antibody responses generally. Overall, heterologous vaccination via mucosal routes may be advantageous for second-generation vaccines.

BackgroundMucosal vaccination may offer increased protection against SARS-CoV-2 compared to parental immunization. Here, we describe immunogenicity and efficacy following viral challenge in non-human primates after intranasal delivery of three unique non-replicating adenoviral vector vaccine (rAd5) candidates.MethodsAfrican green monkeys (AMG) were prime boost immunized 29 days apart with vaccine candidates either expressing the parental spike protein alone (Wuhan-S), spike plus nucleocapsid (Wuhan-S-N), or the spike protein from the beta variant (beta-S). Serum and nasal swabs were collected every 14 days and humoral responses to full length spike (S) and receptor binding domain (RBD) were assessed. All AMGs were challenged with SARS-CoV-2 B.1.351 (beta variant) on day 56. Viral loads measured every two days by TCID50 in nasal washes and bronchial lavage fluid post challenge.ResultsMucosal immunization with Wuhan-S induced significant increases in serum IgG and IgA responses against the homologous parental lineage, as well as beta, delta, and omicron variants. In nasal samples, Wuhan-S immunization elicited over 500-fold increases in in cross-reactive IgA against multiple variants of concern including delta and omicron. While the beta-S rAd5 vaccine candidate induced enhanced serum IgG responses to homologous S and RBD proteins, this approach resulted in less cross-reactive antibodies to other variants compared to Wuhan-S rAd5 vaccine. Despite the differences in the ability to elicit cross-reactive antibody responses, all vaccinated AMGs challenged with SARS-CoV-2 B.1.351 (beta variant), had a significant reduction in viral titers by TCID50 in the nasal passages and reduced viral load in bronchial lavage fluid compared to unvaccinated controls.ConclusionThese results demonstrate mucosal administration of rAd5 clinical candidate vaccine, Wuhan-S, is immunogenic and offers cross-protective humoral responses in both serum and nasal compartments against a mismatched SARS-CoV-2 challenge virus.DisclosuresBecca A. Flitter, PhD, MPH, Vaxart Inc: Stocks/Bonds Sarah N. Tedjakusuma, n/a, Vaxart Inc: Stocks/Bonds Colin A. Lester, n/a, Vaxart Inc: Stocks/Bonds Elena D. Neuhaus, n/a, Vaxart Inc: Stocks/Bonds Susan Johnson, PhD, Vaxart Inc: Stocks/Bonds Emery G. Dora, n/a, Vaxart Inc: Stocks/Bonds Nadine Peinovich, MPH, Vaxart Inc: Stocks/Bonds Clara B. Jegede, n/a, Vaxart Inc: Stocks/Bonds Sean N. Tucker, PhD, Vaxart Inc: Stocks/Bonds.

Abstract SARS-CoV-2 is a highly transmissible respiratory pathogen whose main transmission route is airborne. Development of an animal model and exposure system that recapitulates airborne transmission of SARS-CoV-2 is integral for understanding the dynamics of SARS-CoV-2 spread in individuals and populations. Here we designed, built, and characterized a hamster transmission caging and exposure system that allows for efficient SARS-CoV-2 airborne transmission from an infected index animal to naïve recipients under unidirectional airflow, without contribution from fomite or direct contact transmission. To validate our system, we assessed a 1:1 or 1:4 ratio of infected index to naive recipient hamsters and compared their virological and clinical measurements after eight hours of airborne exposure. Airborne exposure concentrations and pulmonary deposited dose of SARS-CoV-2 in index and naïve hamsters, respectively, were similar in both groups. Daily nasal viral RNA levels, and terminal (day 5) lung viral RNA and infectious virus, and fecal viral RNA levels were statistically similar among 1:1 and 1:4 naive animals. However, virological measurements in the 1:4 naïve animals were more variable than the 1:1 naïve animals, likely due to hamster piling behavior creating uneven SARS-CoV-2 exposure during the grouped 1:4 airborne exposure. This resulted in slight, but not statistically significant, changes in daily body weights between the 1:1 and 1:4 naive groups. Our report describes a multi-chamber caging and exposure system that allowed for efficient SARS-CoV-2 airborne transmission in single and grouped hamsters. This system can be used to better define airborne transmission dynamics and test transmission-blocking therapeutic strategies against SARS-CoV-2.ImportanceThe main route of SARS-CoV-2 transmission is airborne. However, there are few experimental systems that can assess airborne transmission dynamics of SARS-CoV-2 in vivo. Here, we designed, built, and characterized a hamster transmission caging and exposure system that allows for efficient SARS-CoV-2 airborne transmission in Syrian hamsters, without contributions from fomite or direct contact transmission. We successfully measured SARS-CoV-2 viral RNA in aerosols and demonstrated that SARS-CoV-2 is transmitted efficiently at either a 1:1 or 1:4 infected index to naïve recipient hamster ratio. This is meaningful as a 1:4 infected index to naïve hamster ratio would allow for simultaneous comparisons of various interventions in naïve animals to determine their susceptibility of infection by aerosol transmission of SARS-CoV-2. Our SARS-CoV-2 exposure system allows for testing viral airborne transmission dynamics and transmission-blocking therapeutic strategies against SARS-CoV-2 in Syrian hamsters.

BackgroundOral vaccines delivered as tablets offer several advantages over traditional injection-based vaccines including ease of distribution and administration as well as temperature-stable formulation options. Oral vaccination is also advantageous because it directly induces a strong mucosal response, which is thought to be critical for preventing future infections. Here we present results from a phase II clinical challenge study comparing efficacy of an oral recombinant adenovirus-based vaccine expressing hemagluttinin (HA) from A/California 04/09 to that of a commercial injectable quadrivalent (QIV) influenza vaccine.MethodsIn this 2016–2017 clinical trial (NCT02918006), subjects were immunized with either oral vaccine, QIV, or placebo and then challenged 90 days post-immunization with wildtype influenza A H1 virus to measure vaccine efficacy and durability. Protection was assessed by measuring changes in HAI titres, microneutralization, and IgA/IgG ASC assays. Additionally, exploratory flow cytometry evaluated quantitative and qualitative aspects of immunogenicity including markers of activation and mucosal homing on B cells. Analysis was performed on days 0 and 7 post-immunization and 0 and 6 days post-viral challenge. Plasmablasts sorted from PBMCs were then isolated for genomic DNA and sequenced for heavy chain receptor sequencing using NGS analysis.ResultsOf the subjects immunized with Vaxart’s oral tablet vaccine, 48% were protected. QIV, by comparison, protected 38% of immunized individuals. Only 37% of Vaxart subjects developed influenza infection compared with 44% of QIV subjects and 71% of placebo subjects. While both vaccines induced a humoral immune response, FACS analysis and NGS revealed that Vaxart subjects had more activated plasmablasts expressing surface mucosal homing markers and a more diverse B cell population than QIV subjects.ConclusionVaxart’s oral influenza tablet vaccine protected against influenza infection as well or better than injectable QIV. However, the mechanism of protection appears to be unique to the route of immunization; oral immunization allows for specific homing of influenza specific B cells to sites of infection and produces a more diverse antibody repertoire.Disclosures N. Kolhatkar, Vaxart, Inc.: Employee, Salary. K. Gottlieb, Vaxart, Inc.: Employee, Salary. K. Kasparek, Vaxart, Inc.: Employee, Salary. K. Hodgson, Vaxart, Inc.: Employee, Salary. S. Tucker, Vaxart, Inc: Employee, Salary. D. Liebowitz, Vaxart, Inc.: Employee and Investigator, Salary.

An oral gene-based avian influenza vaccine would allow rapid development and simplified distribution, but efficacy has previously been difficult to achieve by the oral route. This study assessed protection against avian influenza virus challenge using a chimeric adenovirus vector expressing hemagglutinin and a double-stranded RNA adjuvant. Immunized ferrets and mice were protected upon lethal challenge. Further, ferrets immunized by the peroral route induced cross-clade neutralizing antibodies, and the antibodies were selective against hemagglutinin, not the vector. Similarly, experiments in mice demonstrated selective immune responses against HA with peroral delivery and the ability to circumvent preexisting vector immunity.