A Phase I clinical trial of a human monoclonal antibody discovered and developed at UMass Chan Medical School for the prevention of Lyme disease in the U.S. 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. TNX-4800 (formerly known as mAb 2217LS), a long-lasting borreliacidal (or bactericidal) was licensed to Tonix Pharmaceuticals Holding Corp., a commercial biotechnology company in Berkeley Heights, N.J. An adaptive Phase 2 field study is expected to begin in the first half of 2027, pending FDA clearance.
“Our study demonstrated potentially protective blood levels of TNX-4800 at two days, with protective blood levels sustained for at least four months due to its extended half-life design,” said Dr. Klempner, professor of medicine. “Additionally, with its differentiated mechanism of action, TNX-4800 has the potential to provide passive immunity by directly supplying neutralizing antibodies, bypassing the need for a vaccine to induce a patient’s immune system to generate its own antibodies, which can be associated with other issues. We look forward to further clinical investigation of TNX-4800 as we strive to overcome this major public health challenge.”
Lyme disease, the most common tick-born illness in the Northern hemisphere, is transmitted to humans through the bite of infected deer ticks ( Ixodes scapularis ). According to the Centers for Disease Control and Prevention estimates, there are more than 450,000 cases annually in the U.S. That number is expected to rise as global changes in climate are expanding habitat range for ticks and other disease vectors.
Typical symptoms of Lyme disease include fever, headache, fatigue and a characteristic skin rash called erythema migrans. If left untreated, infection can spread to the joints, heart and nervous system. While most cases of Lyme disease can be treated successfully with antibiotics, the only way to prevent infection is to avoid tick bites by using insect repellent and removing ticks promptly.
“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,” said Seth Lederman, MD, chief executive officer of Tonix Pharmaceuticals.
“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,” said Dr. Lederman.
Lyme is not caused by the tick directly. It is caused by the bacterium Borrelia burgdorferi present in the gut of infected ticks. When an infected tick bites someone and begins to feed on their blood, Lyme-causing bacteria can slowly travel from the tick’s gut to its salivary glands and then transfer to the site of the bite.
TNX-4800 blocks the maturation of Borrelia burgdorferi in the mid-gut of infected deer ticks. This inactivates the bacteria in the tick before it ever reaches the skin at the site of the tick bite.
Intended to be administered in the early spring before ticks are at their most active, TNX-4800 is expected to provide almost-immediate protection from Borrelia burgdorferi bacteria-caused Lyme disease. A single injection is designed to maintain protective antibody serum concentration, with expected duration of protection approximately four months, providing pre-exposure protection against Lyme without relying on the recipient’s immune system to generate antibodies.
The primary objective of the Phase 1 study was to evaluate the safety and tolerability of a subcutaneous injection of TNX-4800 when administered to healthy male and female subjects 19 to 65 years old. The secondary objective was to evaluate pharmacokinetics when administered to healthy subjects. A total of 44 subjects were enrolled in the study, with 41 completing it. Results showed no significant clinical or laboratory safety signals with most adverse events mild or moderate.
Pending FDA clearance, Tonix plans to initiate a randomized, double-blind, placebo-controlled, adaptive Phase 2 trial in the first half of 2027.