OVX836, a nucleoprotein-based universal influenza A vaccine candidate being developed by Osivax, demonstrated positive safety and immunogenicity data across three dose levels in a phase 2a study, according to new research published in The Lancet Infectious Diseases.

OVX836 is designed to target the nucleoprotein, a highly conserved internal antigen. Unlike surface antigens, the nucleoprotein is much less likely to mutate, alleviating the need for annual vaccination updates, according to a release from Osivax. 

In the OVX836-003 study, 137 healthy subjects aged 18 to 55 years received one intramuscular injection of the study vaccine or placebo as follows: 33 received OVX836 180 μg, 35 received OVX836 300 μg, 36 received OVX836 480 μg, and 33 received a placebo. The OVX836 vaccine was safe and immunogenic at all dose levels. OVX836 elicited significant humoral and cellular nucleoprotein-specific immune responses, including CD4+ and CD8+ T-cells. 

Most of the immunological markers showed a dose-dependent response from 180 µg to 480 µg. Induction of a measurable CD8+ response against a non-adjuvanted recombinant protein vaccine is challenging in humans and rarely reported, thus warranting the further evaluation of OVX836 in larger phase 2b/3 clinical trials. Importantly, OVX836 provided an 84% level of protection against PCR-confirmed symptomatic influenza compared to placebo.

A separate cohort of 100 older adults (65 years old and older) was vaccinated (same doses and randomization ratio as younger subjects) and will be reported separately, with full results expected by the fourth quarter.

“The favorable safety profile and strong dose-dependent immune responses observed in this study underscore the potential of OVX836 as a promising influenza vaccine,” says Isabel Leroux-Roels, PhD, principal investigator at the Center for Vaccinology, in a release. “Notably, the observed signal of protection appears to be in line with the universal influenza vaccine target product profile set by the US National Institutes of Health, which is highly encouraging and certainly warrants closer evaluation in additional clinical trials.”

“The publication of our phase 2a data…is a significant appreciation and recognition of the robust nature of our study results,” adds Alexandre Le Vert, CEO and cofounder of Osivax, in a release. “We are strongly encouraged by these findings, particularly given that very few vaccine candidates pursuing a T-cell mechanism of action targeting the [nucleoprotein] have elicited vaccine efficacy at this point in time. As such, we look forward to advancing OVX836 toward the next stages of clinical development as a truly universal influenza vaccine.”