Osivax's nucleoprotein flu vaccine misses Phase 2b goal with 24% efficacy and pivots to combinations

French biotech Osivax said on 15 October that its nucleoprotein-targeted influenza A vaccine, OVX836, fell short of its primary goal in a Phase 2b field efficacy study of 2,850 healthy adults in Europe, and that it will now develop the shot mainly as a partner to conventional seasonal vaccines rather than on its own ¹.

What the trial found

The study needed to show vaccine efficacy of 50% to meet its primary endpoint. OVX836 managed 24% ¹.

Secondary measures came out in a similar range. Estimated efficacy against CDC-defined influenza-like illness was 28%, and strain-specific estimates were 27% against A/H3 and 25% against A/H1N1pdm09 ¹. Osivax described these numbers as an "emerging pattern for a preliminary VE signal" and said that, as far as it knows, they are the first consistent efficacy signal for a single-component nucleoprotein vaccine across both main influenza A subtypes in a field trial ¹.

The company reported a safety profile in line with earlier studies, and said the shot produced strong antibody and T-cell responses against the nucleoprotein ¹. Unlike the surface proteins targeted by standard flu shots, the nucleoprotein is an internal antigen that changes little between strains, which is the reason for the approach ¹.

What it means for the market

The result moves OVX836 out of the standalone race. Osivax will concentrate on an existing programme that pairs it with other vaccines ¹. In August it took a non-exclusive licence to GC Biopharma's inactivated seasonal flu vaccine, GC FLU, which is approved in South Korea, with a view to combining the two in one product ¹. It also named a "second, undisclosed global pharmaceutical partner" for another combination ¹.

The logic rests on a known weakness of current seasonal vaccines: they raise antibodies against surface proteins that drift over time, so manufacturers reformulate each season and still only partly match circulating strains ¹. Osivax's case is that adding broad cellular immunity on top of strain-specific antibodies could widen protection. Chief executive Alexandre Le Vert put it plainly: "Rather than replacing existing seasonal influenza vaccines, we believe the greatest opportunity lies in complementing them" ¹.

For established flu vaccine makers, that framing turns a would-be competitor into a possible add-on to their products. Earlier evidence for the combination comes from a Phase 2a study of OVX836 with GSK's Fluarix Tetra in 60 healthy volunteers, and from a larger Phase 2 combination study ¹. How the combination will be developed from here, and on what timetable, has not been disclosed.

Caveats

The secondary efficacy figures are point estimates from a study that missed its primary endpoint, and the company itself calls them preliminary ¹. The trial ran only in Europe and tested the vaccine alone, so it says little directly about how the combination will perform. The Phase 2a combination evidence comes from a study of 60 people ¹.

Osivax's next step is the combination route, with GC FLU and with its unnamed second partner ¹.