Tonix Pharmaceuticals (Nasdaq: TNXP) presented Phase I data for TNX-4800, a long-acting anti-OspA human monoclonal antibody being developed for Lyme disease prevention, at the World Vaccine Congress Washington 2026 on March 30, the company said. The data, described as supportive of approximately four months of protection, were drawn from a completed dose-escalation study in healthy adults, according to the company.
The Phase I study enrolled 44 healthy subjects aged 19–65, of whom 41 completed the trial. Participants received a single subcutaneous injection of placebo or TNX-4800 at doses of 0.5, 1.5, 5, or 10 mg/kg. Peak serum concentration increased approximately 25-fold across a 20-fold dose range, and serum levels were detectable at the earliest sampling timepoint of two days post-dose. At the lowest dose, TNX-4800 remained quantifiable for more than 200 days in 80% of subjects; at doses of 1.5 mg/kg and above, levels persisted for up to 350 days in the majority of participants. Mean half-life ranged from 62 to 69 days across active dose cohorts, and serum concentrations remained quantifiable for up to 12 months in most subjects. Mean exposure in the 10 mg/kg cohort was less than 17% of the highest exposures observed in a rat toxicology study. Anti-drug antibodies were detected in fewer than 10% of treated subjects with no apparent impact on pharmacokinetics. Most adverse events were mild or moderate, and the company said no significant clinical or laboratory safety signals were observed.
The study, registered as NCT04863287, had safety and tolerability as its primary endpoint, with pharmacokinetics as the secondary objective. The data remain based on a completed but single-center first-in-human cohort. Tonix said it plans to initiate a randomized, double-blind, placebo-controlled, adaptive Phase II field study in H1 2027, pending FDA clearance, with the aim to evaluate a single 350mg SC dose and four-month protection as the primary endpoint and six-month protection as a key secondary endpoint.
TNX-4800, formerly known as mAb 2217LS, is a borreliacidal human monoclonal antibody with an engineered Fc domain designed to extend serum half-life, targeting OspA on Borrelia burgdorferi – the bacterium (spirochete) that causes Lyme disease, transmitted to humans primarily through the bite of infected ticks. No FDA-approved vaccine or prophylactic for Lyme disease is currently marketed in the United States. VLA15 (Pfizer/Valneva), an OspA-based multivalent vaccine candidate, is in Phase III development and requires a multi-dose immunization schedule, with Pfizer recently indicating an approval filing is under planning.