Tonix Pharmaceuticals Reports Promising Preclinical Data for TNX-801 Mpox Vaccine at World Vaccine Congress
Key Insights
Tonix Pharmaceuticals (search) presented preclinical data for TNX-801, a live attenuated horsepox-based vaccine candidate designed to protect against mpox (search) and smallpox (search) with single-dose administration.
The vaccine demonstrated strong neutralizing antibody responses and protected animals from clinical disease and mortality in non-human primate, rabbit, and murine models for at least 14 months.
TNX-801 showed favorable safety profiles across multiple administration routes and may offer advantages over existing vaccines through durable T-cell responses and potential for large-scale manufacturing.
Tonix Pharmaceuticals (search) Holding Corp. presented encouraging preclinical data for its investigational mpox (search) vaccine TNX-801 at the World Vaccine Congress-Europe 2025 in Amsterdam, demonstrating the potential for a next-generation orthopoxvirus vaccine with durable single-dose protection.
The live, attenuated, minimally replicative vaccine candidate is based on horsepox virus (search) and is being developed to protect against both mpox (search) (monkeypox (search)) and smallpox (search). Preclinical studies showed that TNX-801 produced durable immune protection following a single dose and was well tolerated across multiple routes of administration, including percutaneous, subcutaneous, and intramuscular delivery.
Strong Preclinical Efficacy Across Multiple Models
TNX-801 elicited strong neutralizing antibody responses and protected animals from clinical disease and mortality following mpox (search) challenge in non-human primate, rabbit, and murine models. Immunogenicity and durability were observed for at least 14 months post-vaccination, suggesting the potential for long-lasting protection.
"We are encouraged by the consistency and durability of the TNX-801 data across multiple preclinical models," said Dr. Sina Bavari, Executive Vice President of Infectious Disease Research at Tonix Pharmaceuticals (search), who presented the data. "We are also excited by the opportunity to evaluate microneedle patch technology as a novel delivery platform to simplify administration and expand vaccine accessibility in future development stages."
The vaccine demonstrated particularly promising results in non-human primates, where a single dose vaccination prevented clinical disease and lesions and decreased shedding in the mouth and lungs. These findings are consistent with mucosal immunity and suggest the ability to block forward transmission, similar to Dr. Edward Jenner's original smallpox (search) vaccine.
Potential Advantages Over Current Vaccines
TNX-801 is based on synthesized horsepox, which is believed to be more closely related to Dr. Jenner's vaccine than 20th century vaccinia viruses. The company believes TNX-801 has the potential to make a global impact on mpox (search) and smallpox (search) risk because of its durable T-cell immune response, the potential to manufacture at scale, and the use of a lower dose than non-replicating vaccines.
The current FDA-approved non-replicating mpox (search) vaccine Jynneos requires two doses and provides a relatively short duration of protection. The FDA also recently approved ACAM2000, a live, replicating vaccinia vaccine for prevention of mpox, which is a clone from DryVax, a 20th century vaccinia vaccine derived from the NYCBH strain.
Regulatory Progress and Clinical Development Plans
Tonix has received official written response from a Type B pre-Investigational New Drug Application (IND) meeting with the U.S. Food and Drug Administration to develop TNX-801 as a potential vaccine to protect against mpox (search) disease and smallpox (search). The company has also announced a collaboration with the Kenya Medical Research Institute (KEMRI) to design, plan and seek regulatory approval for a Phase I clinical study of TNX-801 in Kenya.
"Vaccines remain a cornerstone of pandemic preparedness and biodefense," said Seth Lederman, M.D., Chief Executive Officer of Tonix Pharmaceuticals (search). "The data presented in Amsterdam support the potential of TNX-801 as a next-generation orthopoxvirus vaccine candidate with the ability to confer durable protection. We believe TNX-801 has the potential to strengthen global readiness for emerging and re-emerging poxvirus threats."
Competitive Landscape
Recent preclinical results from an mRNA vaccine showed some protection from a Clade I monkeypox (search) challenge, but with multiple breakthrough lesions in vaccinated animals, highlighting the potential advantages of TNX-801's approach. The vaccine's ability to prevent lesions and reduce viral shedding could be particularly important for controlling transmission during outbreaks.
The data support advancement of TNX-801 toward clinical development as the company continues to build its infectious disease portfolio, which also includes treatments for Lyme disease prevention and broad-spectrum antiviral agents for military personnel in biological threat environments.