On Jul. 30, 2020, INOVIO announced that its COVID-19 DNA vaccine INO-4800 targeting SARS-CoV-2 was effective in protecting non-human primates (NHPs; specifically rhesus macaques) from live virus challenge 13 weeks after the last vaccination. These protective results were mediated by memory T and B cell immune responses from INO-4800 vaccination.

These results, submitted to a peer-reviewed journal and also published today on the non-peer reviewed online preprint site bioRxiv, 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, the infection caused by SARS-CoV-2, and the T cell responses were significantly higher than those from convalescent patients.

B cells are responsible for producing the antibodies that recognize SARS-CoV-2, while T cells play a role in killing the virally infected cells as well as supporting the B cell response. The published 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. To INOVIO’s knowledge, this is the first report of vaccine-induced responses driving immunity against G614 variants. A strong anamnestic or memory T and B cell responses were demonstrated following challenge with the live virus.

A separate NHP study evaluating the durability of INO-4800 at 12 months after vaccination is currently under way. INO-4800 also has been selected by U.S. Operation Warp Speed for its COVID-19 non-human primate challenge study.