A COVID-19 DNA vaccine targeting SARS-CoV-2 has proved effective in protecting non-human primates (NHPs; specifically rhesus macaques) from live virus challenge 13 weeks after the last vaccination, with the protective results mediated by memory T and B cell immune responses from the vaccination.

The COVID-19 DNA vaccine, INO-4800, developed by INOVIO Pharmaceuticals, Inc. (Plymouth Meeting, PA, USA) reduced viral load in both the lower lungs and nasal passages in macaques that received two doses of the vaccine (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 NHPs 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.

“All other previously reported NHP vaccine protection studies actually challenged the animals at the peak of their immune response,” said Dr. J. Joseph Kim, President and Chief Executive Officer of INOVIO. “Our study demonstrates that INO-4800 could provide protection in a more real-world setting, where vaccine-generated memory immune responses protected NHPs for more than three months (13 weeks) from the last vaccination. Given the importance of protective antibody and T cell responses, this study gives us more confidence as we continue to advance INO-4800 in the clinic. We believe INO-4800 holds significant potential to help address this global public health crisis.”

"As we eagerly anticipate initiating a Phase 2/3 efficacy trials this summer, an animal challenge is currently the closest thing we have to testing a vaccine's efficacy when confronting a live virus. We are very encouraged with the duration of protection that INO-4800 demonstrated in this NHP study and look forward to reassessing its impact on durability of response at 12 months out from our other ongoing non-human primate and animal challenge studies," said Dr. Kate Broderick, Ph.D., INOVIO's Senior Vice President, Research & Development. "In addition to safety and efficacy, it is essential that any vaccine targeting SARS-CoV-2 generates a relevant durability of response. A vaccine that only provides protection for a very short period of time is not going to realistically solve the problem of this pandemic."

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