Tonix Pharmaceuticals Presents Phase 1 Data of TNX-4800, Plans Phase 2 Study in 2027

Tonix Pharmaceuticals announced Phase 1 data of TNX-4800 was presented at the World Vaccine Congress Washington 2026. Tonix also announced its planned strategy for an adaptive Phase 2 field study expected to initiate in the first half of 2027, pending FDA clearance. TNX-4800 is a long-acting borreliacidal, human monoclonal antibody with an engineered crystallizable fragment domain for an extended half-life that targets the outer surface protein A of Borrelia burgdorferi, which causes 99.9% of Lyme disease cases in the U.S. Tonix is developing TNX-4800, which the company in-licensed from UMass Chan Medical School in 2025, as a prophylactic that is administered in a single subcutaneous dose expected to provide approximately four months protection to people in endemic areas during the U.S. tick season. There are currently no marketed FDA-approved vaccines or prophylactics to protect against Lyme disease. The primary objective was to evaluate the PK of a SC dose of TNX-4800 when administered to healthy subjects. A total of 44 subjects were enrolled, with 41 subjects completing the study. Subjects received a single SC administration of placebo or TNX-4800 at 0.5, 1.5, 5, or 10 mg/kg. Results showed no significant clinical or laboratory safety signals, with most adverse events mild or moderate. Peak serum concentration increased by 25-fold for a 20-times increase in dose. Serum TNX-4800 was measurable at earliest sampling time of two days, indicating rapid systemic absorption. TNX-4800 levels remained quantifiable for greater than200 days in 80% of subjects at the lowest dose, and for up to 350 days in the majority of subjects at higher doses. The mean half-life ranged from 62-69 days across TNX-4800 cohorts. Serum concentrations were quantifiable for up to 12 months in most subjects. Mean exposure for the 10 mg/kg cohort had less than 17% of the highest exposures in a nonclinical toxicology study. The maximum half-life ranged from 81-104 days, with the 10mg/kg cohort at 97 days and 5mg/kg cohort at 87 days. In the 5mg/kg dose cohort, mean serum TNX-4800 concentration was approximately 10 undefined/ml at four months, which was approximately twice the minimum effective concentration, or MEC, calculated from in vitro bactericidal activity, and approximately the MEC from in vitro tick-feeding experiments. These data support Tonix's planned evaluation of protection at four months as the proposed primary endpoint. Pending FDA clearance, the Company plans to initiate an adaptive field study in the first half of 2027. TNX-4800 will be studied in a randomized, double-blind, placebo-controlled, adaptive Phase 2 field study to evaluate the efficacy of a single SC dose of TNX-4800, 350 mg, in preventing the first occurrence of confirmed Lyme disease during the primary efficacy surveillance period. Based on the Phase 1 PK data, a fixed dose of 350 mg was selected for the Phase 2 field study, which is expected to provide exposures comparable to the 5 mg/kg dose evaluated in Phase 1. Participants will include adolescents and adults 16 to 65 years of age in Lyme-endemic areas in the U.S. The primary endpoint will be the prevention of Lyme disease at four months. A key secondary endpoint will be the prevention of Lyme disease at six months. The Company expects to have GMP investigational product available for clinical testing in early 2027. Additionally, if necessary and pending FDA clearance, the Company plans to initiate a controlled human infection model study in 2028.