TNX-1800 is a live attenuated modified horsepox virus vaccine that is designed to express the Spike protein of the SARS-CoV-2 virus and to elicit a predominant T cell response. Horsepox and vaccinia are closely related orthopoxviruses that are believed to share a common ancestor. Tonix’s TNX-1800 vaccine candidate is administered percutaneously using a two-pronged, or “bifurcated” needle. The major cutaneous reaction or “take” to vaccinia vaccine was described by Dr. Edward Jenner in 1796 and has been used since then as a biomarker for protective immunity to smallpox, including in the World Health Organization’s accelerated smallpox eradication program that successfully eradicated smallpox in the 1960’s. The “take” is a measure of functional T cell immunity validated by the eradication of smallpox, a respiratory-transmitted disease caused by variola.
Live replicating orthopoxviruses, like vaccinia or horsepox, can be engineered to express foreign genes and have been explored as platforms for vaccine development because they possess; (1) large packaging capacity for exogenous DNA inserts, (2) precise virus-specific control of exogenous gene insert expression, (3) lack of persistence or genomic integration in the host, (4) strong immunogenicity as a vaccine, (5) ability to rapidly generate vector/insert constructs, (6) readily manufacturable at scale, and (7) ability to provide direct antigen presentation. Horsepox-based vaccines are designed to be single dose, vial-sparing vaccines that can be manufactured using conventional cell culture systems, with the potential for mass scale production and packaging in multi-dose vials.
TNX-1800 was selected by Project NextGen of the National Institutes of Health (NIH) / National Institute of Allergy and Infectious Diseases (NIAID) for Phase 1 development.