BERKELEY HEIGHTS, N.J., July 15, 2026

Tonix Pharmaceuticals announced the publication of new preclinical research in the Journal of Virology demonstrating significant differences in the virulence of mpox virus strains while identifying three new animal models for studying disease pathogenesis. The findings support the continued development of TNX-801, the company’s investigational live attenuated horsepox virus vaccine candidate for the prevention of mpox and smallpox.

Study Reveals Marked Differences in Mpox Virulence

The study compared the 2022 mpox clade IIb outbreak strain with the 2003 clade IIa strain using multiple murine models. Researchers found that the clade IIb virus circulating during the global 2022 outbreak was 100 to 100,000 times less virulent than historical clade IIa isolates. The findings suggest that reduced virulence may have contributed to the widespread global transmission of clade IIb by increasing the likelihood of milder or subclinical infections while providing important insights into the biological differences among emerging mpox variants.

New Animal Models Expand Mpox Research Capabilities

Tonix researchers developed three novel C57BL/6 mouse models lacking interferon-α receptors, interferon-γ receptors, or both, alongside expanded use of the established CAST/EiJ mouse model. These models provide valuable tools for investigating mpox infection, disease progression, and the effectiveness of vaccines and therapeutics against emerging viral subclades. The ability of older CAST/EiJ mice to develop clade IIa infection also supports future studies evaluating long-term vaccine durability and protective efficacy.

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Findings Support Advancement of TNX-801 Vaccine Program

The research strengthens the scientific foundation for TNX-801, Tonix’s investigational live attenuated recombinant horsepox virus vaccine designed to protect against both mpox and smallpox. Currently in pre-IND development, TNX-801 is expected to enter Phase 1 clinical testing in 2027, pending FDA clearance. Conducted at Tonix’s Biosafety Level 3 research facility in Maryland, the study reinforces the company’s broader infectious disease strategy aimed at improving preparedness against emerging orthopoxvirus threats through innovative vaccine development.

Source: Tonix Pharmaceuticals press release