iBio (NYSE American:IBIO) announced that preclinical studies of IBIO-202, its subunit vaccine candidate that targets the nucleocapsid (N) protein of SARS-CoV-2, demonstrated a robust, antigen-specific, memory T-cell response.
Data on commercially available COVID-19 vaccines, all of which target the spike (S) protein, suggests that neutralizing titers are effective, but likely to wane over time. In addition, the robustness of T-cell priming and cellular immunity achieved by S-protein-directed vaccines may not be sufficient to create a durable immune response, especially in the context of emerging variant strains of the virus.
In contrast, the N-protein gene is more conserved and stable than the spike, with 90% amino acid homology and fewer mutations over time. The SARS-CoV-2 N- protein also shares substantial sequence conservation with the nucleocapsid of other coronaviruses.
In addition, the N-protein can induce SARS-specific T-cell proliferation. The IBIO-202 immunization data are consistent with that, as a strong, cytotoxic, memory T-cell response was seen, rather than an inflammatory response.
In the iBio studies, T-cell priming was achieved in both intramuscular and intranasal administration, allowing for the further exploration of multiple routes of administration and their respective benefits.
“Studies of convalescent sera from patients that have recovered from SARS-CoV-2 infection have shown that the combination of N-directed and S-directed immunity is important,” Martin Brenner, Ph.D., iBio’s CSO, said in a statement.
“Accordingly, we believe the N-protein strategy of IBIO-202 may be complementary with existing S-directed vaccines, conferring additional protective effects that more closely mimic the natural immune responses of patients that have cleared the virus,” he added. Additional characterization studies of IBIO-202 are ongoing.
In a new research report, Cantor Fitzgerald analyst Kristen Kluska said T-cell immunity is important for lasting protection from COVID-19 vaccines since antibody titers have been shown to fade after the initial vaccination.
“Thus, we believe that these results suggest that IBIO-202 could potentially lead to a lasting immune response,” she added.
Based on her research into COVID-19 vaccines, “we believe that a multi-antigen approach is best for avoiding potential immunological escape in the case of viral variants,” Ms. Kluska said. “Thus, we believe that the company’s approach is sound and could potentially support the ongoing global vaccination effort.”
