Osivax has been forced to alter the strategy for its influenza vaccine after the shot failed a phase 2b study.
France’s Osivax evaluated the influenza A vaccine, dubbed OVX836, in the mid-phase trial of 2,850 healthy adults in Europe. OVX836 is designed to target a highly conserved internal antigen called the nucleoprotein.
But the shot was only able to demonstrate vaccine efficacy (VE) of 24%, far below the 50% required to hit the study’s primary endpoint, according to the company’s Oct. 15 release.
When it came to secondary endpoints, Osivax argued the vaccine had shown an “emerging pattern for a preliminary VE signal.” Specifically, the company pointed to an estimated CDC-defined influenza-like illness and the strain-specific VE of 28%, as well as VEs of 27% and 25%, respectively, when focusing on the specific influenza strains of A/H3 and A/H1N1pdm09.
OVX836 also demonstrated a favorable safety profile consistent with previous clinical trials and induced robust NP-specific antibody and T-cell responses, the biotech said.
“To Osivax’s knowledge, these findings represent the first consistent efficacy signal for a monovalent nucleoprotein-based influenza vaccine across both major influenza A subtypes in a field efficacy trial,” the company said in the release.
“Large efficacy studies are designed not only to evaluate clinical benefit, but also to deepen our understanding of novel immune mechanisms under real-world conditions," Osivax’s chief medical officer, Nicola Groth, M.D., said in a statement
“While the study did not meet its primary endpoint, the consistency of the efficacy signal across influenza A subtypes, together with the observed immunogenicity and favourable safety profile, reinforces our confidence that nucleoprotein-targeted immunity can provide a complementary mechanism of protection alongside conventional seasonal influenza vaccines,” Groth added.
In response to the monotherapy results, Osivax will be focusing its ambitions for the vaccine on an existing program assessing OVX836 in combination with other vaccines. To this end, Osivax secured a non-exclusive license in August to GC Biopharma’s inactivated seasonal influenza vaccine.
The GC FLU vaccine, which is approved in GC's home territory of South Korea, is designed to trigger antibody responses against hemagglutinin surface antigens from A and B forms of the flu virus. Osivax’s idea is to combine GC FLU and OVX836 into one vaccine.
The combo vaccine approach reflects evidence that adding OVX836 to a traditional flu vaccine could broaden protection against influenza A. Vaccines such as GC FLU induce antibody responses against proteins on the surface of flu viruses. Because the prevalent surface proteins change over time, manufacturers need to update vaccines for each season and even then only partly hit the moving target, diminishing efficacy.
Osivax generated early evidence to support that idea in a phase 2a study that tested OVX836 with GSK’s Fluarix Tetra. The biotech came away from the trial, which enrolled 60 healthy volunteers, believing that synergistic immune responses and broader cross-protection could make the combination more effective than current monotherapy vaccines. Osivax also tested the combination in a larger phase 2 study.
Another option involves combining OVX836 with a vaccine from a “second, undisclosed global pharmaceutical partner,” according to today's release.
Osivax CEO Alexandre Le Vert said this morning’s phase 2 results “provide a clear direction for the future development of OVX836.”
“Rather than replacing existing seasonal influenza vaccines, we believe the greatest opportunity lies in complementing them,” Le Vert added. “By combining strain-specific antibody protection with the broad cellular immunity induced by OVX836, we aim to develop next-generation influenza vaccines capable of delivering broader and more durable protection against seasonal influenza.”
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