TNX-4800 targets OspA to block Borrelia transmission; positive phase 1 data reported and an adaptive phase 2/3 study is planned.
Tonix In-Licenses TNX-4800, Long-Acting Monoclonal Antibody for Seasonal Lyme Disease Prevention
Image credits: Tonix
Tonix Pharmaceuticals said it has in-licensed worldwide rights to TNX-4800 (formerly 2217LS), a long-acting human monoclonal antibody targeting outer surface protein A (OspA) of Borrelia burgdorferi for once-seasonal, pre-exposure prophylaxis against Lyme disease. The company reports positive phase 1 data showing safety, tolerability, and a linear pharmacokinetic:pharmacodynamic:efficacy relationship and plans an adaptive phase 2/3 study. Tonix notes there are currently no FDA-approved human vaccines or prophylactic antibodies for Lyme disease and estimates roughly 70 million U.S. residents live in endemic areas who could be candidates if efficacy is demonstrated.
TNX-4800 is intended as a single subcutaneous dose in the spring to maintain protective antibody titers through the fall tick season. By binding OspA in the tick midgut, the antibody is designed to block maturation of B. burgdorferi and prevent transmission to humans. The program originated at UMass Chan Medical School, which licensed the technology to Tonix. Company statements highlight rapid onset of protection within two days in the proposed seasonal model.
The antibody incorporates LS Fc substitutions to extend half-life, aiming for season-long coverage after one dose without relying on host seroconversion. Preclinical work with 2217/2217LS has shown prevention of transmission from infected ticks to animals. Tonix positions TNX-4800 as an alternative to multidose OspA vaccine schedules under development and says it intends to advance the program through additional clinical trials with the goal of submitting a biologics license application.
TNX-4800 is designed as a single spring dose to maintain protective antibody levels through the fall tick season by binding OspA in the tick midgut.
Tonix reports favorable phase 1 safety and tolerability with a linear PK/PD/efficacy relationship and plans an adaptive phase 2/3 trial.
With no FDA-approved human Lyme vaccines or prophylactic antibodies, TNX-4800 could address roughly 70 million U.S. residents in endemic areas if efficacy is proven.
For clinicians, the claims regarding immediate protection and single-dose seasonal coverage remain company assertions pending prospective human efficacy data. Until clinical benefit is established and authorized, standard tick-avoidance measures and timely evaluation of suspected Lyme disease remain the cornerstone of prevention and care.
Drawing on an article by Paul O Gubbins, PharmD, and Richard Charles, BPharm, from July 10, 2025, their piece underscored why Lyme prevention tools are gaining urgency. They describe how overlapping forces—warmer, longer seasons and shifting microclimates, land-use changes that favor deer and small-mammal hosts, and expanded surveillance—are driving Ixodes tick range into new latitudes and elevations across North America and Europe. With an estimated 476,000 U.S. cases treated annually and Canadian reports rising sharply, tick exposure is starting earlier in spring, lasting later into fall, and appearing in places that historically saw little risk. Because nymphs account for most human transmission, interventions timed before peak nymph activity make conceptual sense.
That context dovetails with a seasonal, single-dose prophylaxis approach like TNX-4800. A spring administration designed to maintain protective antibody levels through the tick season maps onto the extended risk window described by Gubbins and Charles, and could be relevant not only for residents of endemic regions but also for travelers and seasonal workers entering newly endemic areas. Even if an antibody strategy proves effective in trials, it would complement, not replace, standard prevention measures (tick avoidance, prompt removal) and clinical vigilance, which remain essential as Lyme’s geography and season continue to expand.
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