CHATHAM, N.J. — December 29, 2025 — Leads & Copy — Tonix Pharmaceuticals Holding Corp. (Nasdaq: TNXP) announced updates to its TNX-4800 program, a long-acting human monoclonal antibody (mAb) targeting the outer surface protein A (OspA) of Borrelia burgdorferi, the cause of Lyme disease in humans.
TNX-4800 (formerly known as mAb 2217LS) is being developed for annual seasonal use, administered once subcutaneously in the spring to protect against Lyme disease through the fall, covering the entire tick season in the U.S.
Tonix plans to meet with the FDA in 2026 to explore Phase 2/3 development options, including a controlled human infection model (CHIM) study using Borrelia-infected ticks to mimic natural infection.
The company expects to have investigational product manufactured under Good Manufacturing Practices (GMP) available for testing in early 2027.
According to Tonix, approximately 70 million people in the U.S. who live, work, or vacation in Lyme disease-endemic areas could benefit from pre-exposure prophylaxis.
CEO Seth Lederman, M.D., believes TNX-4800’s long-acting mAb prophylaxis could play a vital role in preventing Lyme disease for millions, offering near-immediate immunity after a single administration, distinguishing it from current Lyme disease vaccine programs.
TNX-4800 delivers a well-characterized antibody directly, blocking the transmission of major Borrelia genospecies from ticks to animals and sidestepping the multidose schedules required for OspA vaccines.
A randomized, double-blind, sequential dose-escalation study (NCT04863287) evaluated the safety, tolerability, pharmacokinetics (PK), and immunogenicity of TNX-4800 in healthy adults.
The study found that drug exposure increased approximately 25-fold for a 20-fold increase in dose. Serum TNX-4800 was measurable at 24 hours, indicating rapid systemic absorption. TNX-4800 concentrations remained quantifiable for over 200 days in 80% of volunteers at the lowest dose and up to 350 days in the majority of volunteers at higher doses. Mean half-life ranged from 62–69 days across groups, and serum concentrations remained quantifiable for up to 12 months in most subjects.
Anti-drug antibodies (ADA) were detected in less than 10% of treated subjects, with no impact on PK. Most adverse events were mild or moderate, and TNX-4800 was generally safe and well-tolerated.
In the United States, Lyme disease is caused by the bacterium Borrelia burgdorferi, with the highest incidence in the Northeast, mid-Atlantic, and upper-Midwest regions.
Tonix intends to advance TNX-4800 through additional clinical trials to submit a Biologics Licensing Application (BLA) to the FDA.
Two long-acting monoclonal antibody products have received FDA approval for prophylaxis against respiratory syncytial virus (RSV): AstraZeneca’s Beyfortus™ (nirsevimab) and Merck’s Enflonsia™ (clesrovimab).
Tonix Pharmaceuticals is a fully-integrated biotechnology company with marketed products and a pipeline of development candidates. Tonix markets FDA-approved TONMYA™, a non-opioid analgesic for fibromyalgia, as well as Zembrace® SymTouch® (sumatriptan injection) and Tosymra® (sumatriptan nasal spray) for acute migraine in adults.
Tonix’s development portfolio is focused on central nervous system (CNS) disorders, immunology, immuno-oncology, rare disease and infectious disease. TNX-102 SL is being developed to treat acute stress reaction and acute stress disorder, as well as major depressive disorder. Tonix’s immunology development portfolio consists of biologics to address organ transplant rejection, autoimmunity and cancer, including TNX-1500. Tonix’s rare disease portfolio includes TNX-2900, in development for Prader-Willi syndrome and expected to start a potential pivotal Phase 2 study in 2026. Tonix’s infectious disease portfolio includes TNX-801, a vaccine in development for mpox and smallpox, as well as TNX-4800. Finally, TNX-4200 for which Tonix has a contract with the U.S. DoD’s Defense Threat Reduction Agency (DTRA) for up to $34 million over five years, is a small molecule broad-spectrum antiviral agent targeting CD45 for the prevention or treatment of high lethality infections.
Investor Contacts:
Jessica Morris
Tonix Pharmaceuticals
investor.relations@tonixpharma.com
(862) 799-8599
Brian Korb
astr partners
(917) 653-5122
brian.korb@astrpartners.com
Media Contacts:
Mary Ann Ondish
Tonix Pharmaceuticals
maryann.ondish@tonixpharma.com
Ray Jordan
Putnam Insights
ray@putnaminsights.com
Source: Tonix Pharmaceuticals
