Immunogenicity, safety, and tolerability of a β-glucan-CpG-adjuvanted respiratory syncytial virus vaccine in Japanese healthy participants aged 60 to 80 years: A phase 2, randomized, double-blind, dose-finding study

VN-0200 is an investigational β-glucan-CpG-adjuvanted respiratory syncytial virus (RSV) vaccine (antigen: VAGA-9001a [RSV F glycoprotein], adjuvant: MABH-9002b). This multicenter, randomized, double-blind, dose-finding phase 2 study explored the optimal VN-0200 dose and confirmed its humoral and cellular immunity and safety. In total, 342 healthy Japanese participants aged 60 to 80 years were randomized to one of 10 vaccination groups, each receiving a different combination of VAGA-9001a and MABH-9002a. VN-0200 was administered intramuscularly on Day 1 and Day 29. Geometric mean titer (GMT) and geometric mean fold rise (GMFR) of neutralization activity for anti-RSV subgroups A (RSV/A) and B (RSV/B), anti-VAGA-9001a antibody titer, and VAGA-9001a-specific interferon (IFN)-γ response were evaluated. Safety was monitored throughout the study. GMTs of serum anti-RSV/A neutralization activity increased from baseline to Day 57 and lower limits of the 95% confidence intervals of the corresponding GMFRs were >1.0 relative to baseline in all treatment groups (primary endpoint). Findings were similar for anti-RSV/A (Day 29) and anti-RSV/B (Day 29 and Day 57) neutralization activity, anti-VAGA-9001a antibody titer (Day 29 and Day 57), and VAGA-9001a-specific IFN-γ response (Day 29 and Day 57) (secondary endpoints). There was no clear influence of adjuvant or dose - response relationship of the antigen or adjuvant for any of the study endpoints. There were no serious vaccine-related treatment-emergent adverse events (TEAEs) or vaccine-related TEAEs leading to death. All antigen/adjuvant dose combinations of VN-0200 were well tolerated and elicited an increase in anti-RSV/A and anti-RSV/B neutralization activity from baseline to Day 29 and Day 57.