On Jun. 18, 2020, Tonix Pharmaceuticals announced an expansion of its strategic collaboration with Southern Research to include a study of T cell immune responses to SARS-CoV-2 in volunteers who have recovered or remain asymptomatic after exposure to COVID-19. The research is part of an ongoing and broader collaboration between Tonix and Southern Research to develop and conduct animal testing of Tonix’s TNX-1800, which is a live replicating virus vaccine designed to protect against COVID-19. The data will support the interpretation of animal trial results with TNX-1800, which are expected in the fourth quarter of 2020 and subsequent human trials.

TNX-1800 is a live modified horsepox virus vaccine for percutaneous administration that is designed to express the Spike protein of the SARS-CoV-2 virus that causes COVID-19 and to elicit a predominant T cell response.  TNX-1810, TNX-1820 and TNX-1830 are modified horsepox viruses that are designed to express different SARS-CoV-2 proteins than Spike and to elicit almost pure T cell responses.  TNX-801 is a live horsepox virus vaccine. 

Horsepox and vaccinia are closely related orthopoxviruses that are believed to share a common ancestor.  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. Relative to vaccinia, horsepox has substantially decreased virulence in mice.  TNX-801 vaccinated macaques showed no overt clinical signs after monkeypox challenge.  Horsepox-based vaccines are designed to be single dose, vial-sparing vaccines, which can be manufactured on conventional cell culturing systems, with the potential for mass scale production.