PHASE 3 STUDY OF SAFETY AND IMMUNOGENICITY OF GBP510 VACCINE ADJUVANTED WITH AS03 IN ADULTS

INTRO: GBP510 contains the self-assembling recombinant nanoparticle displaying SARS‐CoV-2 Spike protein receptor binding domain and is adjuvanted with AS03. We report interim Phase 3 study (NCT05007951) results up to 4 weeks post-dose 2 (Data-cut: March-18-2022), where immunogenicity to the D614G ancestral strain and safety of 25μg GBP510/AS03 candidate was compared to ChAdOx1-S (Vaxzevria). METHODS: This Phase 3 randomized, active-controlled, observer-blind, parallel- group study in adults was conducted in 6 countries. Cohort1: 1,895 subjects (naïve to COVID-19 vaccination and infection) randomized at 2:1 ratio (GBP510/AS03:ChAdOx1-S) to assess immunogenicity and safety; Cohort 2: 2,141 subjects at 5:1 ratio, regardless of their serostatus at screening for safety assessment. Subjects were vaccinated twice at a 4-week interval with 0.5 mL of the test vaccine (GBP510/AS03) or active control (ChAdOx1-S) in deltoid muscle. The primary objective was to demonstrate the superiority of geometric mean titer (GMT) and non-inferiority in seroconversion rate (SCR: ≥4-fold rise from baseline) of neutralizing antibodies over ChAdOx1-S by live-virus neutralization assay (FRNT). FINDINGS: At 2 weeks post-dose 2, GMT ratio of the two groups (Test vaccine/Active control) was 2.93 [95% CI: 2.63, 3.27], satisfying the hypothesis of superiority (95% CI lower limit> 1). The SCR difference (Test vaccine – Active control) was 10.76% [95% CI: 7.68, 14.32], satisfying the hypothesis of non- inferiority (95% CI lower limit> -5%). Good cell-mediated immune responses for Th1 cytokines were also observed with the test vaccine (FluoroSpot). The AE incidence rate for the test vaccine was higher than the active control for solicited local AEs (56.69% vs 49.20%), and comparable for solicited systemic AEs (51.21% vs 53.51%) and unsolicited AEs (13.34% vs 14.66%) after any vaccination. CONCLUSION: Higher immune responses were observed with GBP510/AS03 compared to ChAdOx1-S against D614G strain after 2 weeks post-dose 2. GBP510/AS03 showed a clinically acceptable safety profile; no safety concerns were identified during the study period.