These results demonstrate that INO-4800 reduced viral load in both the lower lungs and nasal passages in macaques that received two doses of INO-4800 (1 mg) four weeks apart and then were challenged with live virus 13 weeks after the second dose (study week 17). The reduced viral loads following exposure to SARS-CoV-2 infection at this timeframe demonstrate an important durable impact mediated by INO-4800. This is the first time a vaccine protection in non-human primates was reported from memory immune responses as previously reported monkey vaccine challenge studies were conducted at the time near their peak immune responses (1-4 weeks from their last vaccination).
INO-4800-treated animals demonstrated seroconversion after a single vaccination, with protective neutralizing antibodies and T cells lasting in their blood more than four months after the initial dose. The antibody levels were similar to or greater than those seen in patients who have recovered from COVID-19, and the T cell responses were significantly higher than those from convalescent patients.
The data support that immunization with INO-4800 limits active viral replication and has the potential to reduce severity of disease, as well as reduced viral shedding in the nasal cavity. In the study, researchers assessed the ability of INO-4800 to induce acute and memory T cell and B cell immune responses, including neutralizing antibody responses against both early virus as well as now-dominant G614 mutant variants.
Phase II/III efficacy trials are expected to begin this summer.