A Phase I clinical trial of a human monoclonal antibody developed at UMass Chan Medical School for the prevention of Lyme disease was well tolerated and showed lasting serum concentrations in participants, according to data presented by Mark Klempner, MD, at the World Vaccine Congress 2026 in Washington D.C. The antibody, known as TNX-4800 (formerly mAb 2217LS), was licensed to Tonix Pharmaceuticals Holding Corp., which is planning an adaptive Phase 2 field study pending clearance from the Food and Drug Administration.
Lyme disease is the most common tick-borne illness in the Northern hemisphere. It is transmitted through bites from infected deer ticks. The Centers for Disease Control and Prevention estimates there are more than 450,000 cases each year in the United States. Experts expect this number to rise as climate change expands tick habitats.
Seth Lederman, MD, chief executive officer of Tonix Pharmaceuticals said, "TNX-4800 is expected to provide a preventative option to the 87 million people in the United States who are at high risk of contracting the disease because they live, work or vacation in a tick-endemic area." Lederman also said, "As a monoclonal antibody, we believe TNX-4800 offers significant advantages over vaccines in development. Lyme disease vaccines that elicit antibodies to OspA [a protein found on the outer membrane of the bacterium that causes Lyme disease] currently in development take more than six months to offer protection and require complex immunization schedules. A previously approved anti-OspA vaccine was withdrawn due to poor uptake, potentially relating to its complex immunization schedule."
The bacterium Borrelia burgdorferi causes Lyme disease when transferred from an infected tick's gut during feeding. TNX-4800 works by blocking maturation of Borrelia burgdorferi within ticks before it can reach humans through a bite.
The treatment is intended for administration early each spring before peak tick activity and aims to provide immediate protection lasting about four months after just one injection. This approach does not rely on recipients' immune systems generating their own antibodies.
The primary goal of this first-phase study was evaluating safety and tolerability among healthy adults aged 19–65 years old; out of 44 enrolled subjects, 41 completed participation with no significant safety concerns observed—most adverse events were mild or moderate. If approved by regulators, Tonix plans a randomized Phase II trial starting next year.
