Randomized, Double-Blind, Reference-Controlled, Phase 2a Study Evaluating the Immunogenicity and Safety of OVX836, A Nucleoprotein-Based Influenza Vaccine

Abstract

OVX836 is a recombinant protein-based vaccine targeting the highly conserved influenza nucleoprotein (NP), which aims to confer a broad-spectrum protection against influenza. In a Phase 1 study, OVX836, administered intramuscularly, has been found safe and immunogenic. The 90µg and 180µg dose levels were selected to be further evaluated in this randomized, monocenter, reference-controlled (Influvac Tetra™: quadrivalent seasonal influenza subunit vaccine), parallel group, double-blind, Phase 2a study in 300 healthy volunteers, aged 18-65 years, during the 2019/2020 flu season. Safety, influenza-like illness episodes (ILI; based on the Flu-PRO^® questionnaire) and immunogenicity were assessed up to 180 days post-vaccination. OVX836 was safe and presented a reactogenicity profile similar to Influvac Tetra. It induced a significant increase in terms of NP-specific interferon-gamma (IFNγ) spot forming cells (SFCs), NP-specific CD4+ T-cells (essentially polyfunctional cells) and anti-NP IgG responses. OVX836 was superior to Influvac Tetra for all immunological parameters related to NP, and the 180µg dose was significantly superior to the 90µg dose for SFCs and CD4+ T-cells expressing IFNγ. Both the CD4+ T-cell and the anti-NP IgG responses persisted up to Day 180. An efficacy signal was observed with OVX836 at 180µg through reduction of ILI episodes occurring during the flu season as of 14 days post-vaccination. In conclusion, these results encourage further clinical evaluation of OVX836 in order to confirm the signal of efficacy on ILIs and/or laboratory-confirmed influenza cases. NCT04192500 (https://clinicaltrials.gov/ct2/show/study/NCT04192500).

Keywords: Influvac Tetra; OVX836; immunogenicity; influenza; nucleoprotein; safety; subunit; universal vaccine.

Figure 1

Evolution over time of the number of nucleoprotein (NP)-specific interferon-gamma (IFNγ) spot forming cells (SFCs) per million of peripheral blood mononuclear cells (PBMC) between baseline (Day 1 – pre-vaccination) and Day 180 (post-vaccination) in the three treatment groups (Influvac Tetra™, OVX836 90µg and OVX836 180µg; per protocol cohort). Results are shown as mean ± standard error; paired comparisons between each timepoint post-vaccination and baseline (Day 1): *p<0.05; ****p<0.0001. Panel (A) corresponds to all subjects, Panel (B) to subjects aged 18-49 years and Panel (C) to subjects aged 50-65 years.

Figure 2

Frequencies of nucleoprotein (NP)-specific CD4+ T-cells identified in vitro as expressing the combinations of cytokines: IFNγ, IL-2 and TNFα at pre-vaccination, Day 1 (D1), Day 8 (D8), Day 29 (D29) and Day 180 (D180) in the three treatment groups (Influvac Tetra™, OVX836 90µg and OVX836 180µg; modified intention-to-treat cohort). Results are shown as box plot with the horizontal central bar corresponding to the median, limits of the box corresponding to percentiles 25 and 75, and vertical bars corresponding to percentiles 10 and 90. Intragroup differences: *p<0.05, **p<0.01 and ***p<0.0001; paired t tests versus baseline. Main intergroup differences (global ANOVA with p value <0.05 at each timepoint and post-hoc t tests between OVX836 90 µg and OVX836 180 µg with p values <0.05) were as follows: - IL2+/TNFα+/IFNγ+: Day 8 global p=0.012, Day 29 global p<0.0001, Day 180 global p<0.0001. - IL2+/TNFα-/IFNγ+: Day 8 global p<0.0001, Day 29 global p<0.0001 (OVX836 180 µg versus OVX836 90 µg p=0.008), Day 180 global p<0.0001 (OVX836 180 µg versus OVX836 90 µg p=0.026). - IL2+/TNFα+/IFNγ-: Day 8 global p=0.036, Day 29 global p<0.0001, Day 180 global p<0.0001. - IL2-/TNFα+/IFNγ+: Day 8 global p<0.0001, Day 29 global p=0.001. - IL2-/TNFα-/IFNγ+: Day 8 global p<0.0001 (OVX836 90 µg versus OVX836 180 µg p=0.002), Day 29 global p<0.0001 (OVX836 90 µg versus OVX836 180 µg p<0.0001). - IL2+/TNFα-/IFNγ-: Day 8 global p<0.0001 (OVX836 90 µg versus OVX836 180 µg p=0.026), Day 29 global p<0.0001, Day 180 global p=0.003. - IL2-/TNFα+/IFNγ-: No statistically significant differences (global p values>0.05).

Figure 3

Panel (A) Number of nucleoprotein (NP)-specific interferon-gamma (IFNγ) spot forming cells (SFCs) per million peripheral blood mononuclear cells (PBMC) at baseline (Day 1 – pre-vaccination) and Day 8 (post-vaccination) in the three treatment groups (Influvac Tetra™, OVX836 90µg and OVX836 180µg; modified intention-to-treat cohort after elimination of two outlier subjects with very high values at baseline). Results are shown as mean ± standard error; intergroup comparisons: *p<0.05; **p<0.01; ****p<0.0001. Panel (B) Percentage of NP-specific CD4+ T-cells positive for at least IFNγ at baseline (Day 1 – pre-vaccination) and Day 8 (post-vaccination) in the three treatment groups (modified intention-to-treat cohort). Results are shown as mean ± standard error; intergroup comparisons: **p<0.01; ****p<0.0001. Panel (C) Anti-NP immunoglobulin G (IgG) titers at baseline (Day 1 – pre-vaccination) and Day 8 (post-vaccination) in the three treatment groups (modified intention-to-treat cohort). Results are shown as geometric mean titers ± 95% confidence interval; intergroup comparisons: ****p<0.0001.

Figure 4

Panel (A) Percentage of subjects reporting mild (light color) or moderate (dark color) solicited local signs during the 7-day post-vaccination period in the three treatment groups (Influvac Tetra™, OVX836 90µg and OVX836 180µg; modified intention-to-treat cohort corresponding to the safety cohort). Panel (B) Percentage of subjects reporting mild (light color), moderate (intermediate color) or severe (dark color) solicited systemic symptoms during the 7-day post-vaccination period in the three treatment groups and safety cohort. Panel (C) Percentage of subjects reporting unsolicited adverse events (AEs) (light color) and severe AEs (grade 3; dark color), overall and considered related to the vaccine by the investigator, during the 28-day post-vaccination period, in the three treatment groups and safety cohort.

Figure 5

Kaplan-Meier survival analysis of the cumulative risk of influenza-like illness (ILI) as a function of time between vaccination and first ILI episode (day) during the influenza season (defined as the period between 02 December 2019 and 09 March 2020), from 14 days post-vaccination onward, in the three treatment groups (Influvac Tetra™, OVX836 90µg and OVX836 180µg; modified intention-to-treat cohort corresponding to the safety cohort). Log-rank test showed a p=0.054 for the comparison between Influvac Tetra and OVX836 90µg.