Seth Lederman, MD, cofounder, CEO, and chairman at TONIX Pharmaceuticals

Seth Lederman, MD 

As attention returns to the ongoing challenges surrounding Lyme disease prevention, a new approach may offer a faster, more flexible alternative to traditional vaccines. 

At the World Vaccine Congress Washington 2026, Tonix Pharmaceuticals

 presented phase 1 data on TNX-4800, a long-acting monoclonal antibody designed to provide rapid, single-dose protection against Lyme disease.

Unlike vaccines currently in development, which can take months and require multiple doses to achieve immunity, TNX-4800 is engineered to deliver passive immunity within days—potentially reaching protective levels in as little as 48 hours and lasting through peak tick season. With approximately 87 million Americans living in Lyme-endemic areas and no approved prophylactic currently available, this innovation could represent a meaningful shift in prevention strategies, particularly for high-risk populations such as outdoor workers and travelers.

) asked Seth Lederman, MD, cofounder, CEO, and chairman at TONIX Pharmaceuticals, about TNX-4800 and monoclonal antibodies.

: From an infection prevention perspective, how significant is the potential for a single-dose monoclonal antibody to provide rapid protection against Lyme disease compared with traditional vaccine approaches?

 TNX-4800 has the potential to make a meaningful difference for the prevention of Lyme disease and offers significant advantages over vaccines in development. TNX-4800 is a human monoclonal antibody against OspA that targets 

, the serotype that causes 99.9% of Lyme disease in the US. This is the OspA that matters most for the US, which is why Tonix is targeting it. TNX-4800 is expected to be delivered in one subcutaneous dose.

A phase 1 study of TNX-4800 demonstrated potentially protective blood levels at 2 days, with these levels sustained for at least 4 months due to its extended half-life design. The results support our adaptive phase 2 field study plans for the first half of 2027, pending US Food and Drug Administration (FDA) clearance. The primary end point will be the prevention of Lyme disease at 4 months, and a key secondary end point will be the prevention of Lyme disease at 6 months

However, Lyme disease vaccines that elicit antibodies to OspA currently in development take more than 6 months to offer protection and require complex immunization schedules, which can be a major burden for people. Another difference is that while TNX-4800 offers passive immunity, meaning protection is not dependent on the patient’s immune system mounting a response, vaccines rely on active immunization, meaning you’re asking the body to generate its own immune response over time, often requiring multiple doses spread over months. That inherently introduces delays, complexity, and adherence challenges.

: How could a 2-day onset of protection change real-world prevention strategies, particularly for high-risk populations such as outdoor workers or travelers entering endemic areas?

 Lyme disease is a daunting issue for the approximately 87 million Americans who live, work, or travel in endemic areas.

With TNX-4800, we are providing a potential solution in which one subcutaneous shot could confer immunity within 2 days and provide protection for at least 4 months. However, vaccines take more than 6 months to provide protection and require complex immunization schedules, often leading to adherence issues.

Therefore, if approved, TNX-4800 could offer a noticeable shift in how people can prevent infection with Lyme disease-causing bacteria. TNX-4800 has the potential to be a more practical, convenient, and adaptable prevention measure because people can plan less far in advance and have coverage with fewer steps. They could also plan to receive it with greater flexibility, such as in advance of short-term trips to endemic areas.

: What are the advantages and potential limitations of passive immunity using monoclonal antibodies vs active immunization for seasonal infectious diseases?

 Monoclonal antibodies, such as TNX-4800, may be delivered subcutaneously, including in patients with partially functional immune systems. TNX-4800 provides passive immunity by directly supplying neutralizing antibodies, bypassing the need for a patient’s immune system to generate its own antibodies. This is important, as it potentially expands the population of people who can receive the drug, such as the elderly and immunocompromised people. We are pleased to see growing clinical and market acceptance of monoclonal antibody preventive treatments, including for respiratory syncytial virus (RSV) and COVID-19.

However, for Lyme disease vaccines under development, people must generate antibodies with their own immune systems. These vaccines typically take more than 6 months to be protective, depend on high-titer antibodies, require annual boosters, and have complex immunization schedules that could lead to poor uptake.

: Given the estimated 87 million Americans at risk, how might TNX-4800 fit into broader public health and IPC strategies for vector-borne disease prevention?

 Lyme disease is a serious public health issue in the US that Tonix is committed to addressing. TNX-4800 could be an important preventative option for the approximately 87 million people who live, work, or travel in endemic areas as other systemic mitigation efforts continue. Given that TNX-4800 is expected to be protective within 2 days and provide coverage for at least 4 months, it could be a practical tool as part of a broader effort to prevent Lyme disease that includes education and practical techniques to limit risk.

: What key factors should infection prevention professionals watch for as TNX-4800 moves into phase 2, particularly regarding durability, uptake, and real-world effectiveness?

 We are focused on preparations for initiating an adaptive field study in the first half of 2027, pending FDA clearance. This year, in 2026, we are making the GMP investigational product for clinical testing in early 2027.

In the adaptive phase 2 field study, participants will include adolescents and adults aged 16 to 65 years in Lyme-endemic areas of the US. The primary end point will be the prevention of Lyme disease at 4 months (comparison between the TNX-4800 and placebo groups). A key secondary end point will be the prevention of Lyme disease at 6 months (TNX-4800 vs placebo). If necessary and pending FDA clearance, we plan to initiate a controlled human infection model (CHIM) study in 2028.

We look forward to making progress and keeping the field posted about our developments.

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A potential shift in Lyme disease prevention: TNX-4800, a single-dose monoclonal antibody, demonstrated rapid protection within 2 days and up to 4 months of coverage in phase 1 data. Could this redefine prevention strategies for millions in Lyme-endemic regions? 

Seth Lederman, MD

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Lyme Disease Prevention Breakthrough? TNX-4800 Monoclonal Antibody Shows Rapid Protection in Phase 1 Data at World Vaccine Congress 2026