Tonix Plans Adaptive Phase 2 Trial for Seasonal Lyme Disease Prevention Therapy, Advances Program Following FDA Type C Meeting

Tonix Pharmaceuticals has received the official meeting minutes from a Type C meeting with the U.S. Food and Drug Administration (FDA) regarding its planned adaptive Phase 2 field study of TNX-4800, an investigational monoclonal antibody designed to help prevent Lyme disease in adults. The therapy targets outer-surface protein A (OspA) on Borrelia bacteria carried by infected deer ticks, a well-established target for preventing Lyme disease.

Unlike traditional vaccines, TNX-4800 is being developed as a seasonal immunopreventive therapy, offering temporary protection during periods of high tick exposure. The monoclonal antibody has been Fc-modified to extend its half-life and provide longer-lasting protection, making it a potential alternative for individuals who may benefit from seasonal prevention rather than vaccination.

“Our focus in 2026 has been on manufacturing investigational product for TNX-4800, which is on track for delivery to study sites in the first quarter of 2027,” said Zeil Rosenberg, M.D., Executive Vice President, Medical at Tonix. “The official FDA minutes indicate alignment on a randomized, placebo-controlled adaptive field study design enrolling approximately 3,300 adult participants over two seasons with a primary efficacy endpoint of Lyme disease prevention through six months after the first dose, and a key secondary efficacy endpoint of prevention through three months. The primary safety objective will be to evaluate the safety and tolerability of TNX-4800 over a 52-week period after dosing. We expect the majority of participants will be enrolled in the 2028 season. If the attack rate is lower than expected, enrollment could potentially extend into 2029.”

The planned Phase 2 adaptive field study will randomly assign participants in a 1:1 ratio to receive either TNX-4800 (450 mg administered subcutaneously) or a placebo. Approximately three months later, participants will receive a second dose of either the investigational therapy or placebo to evaluate its protective effect over the Lyme disease season.

“We appreciate the constructive feedback from the FDA on the design of the planned adaptive Phase 2 field study of TNX-4800, Tonix’s long-acting mAb to prevent Lyme disease in the U.S.,” said Seth Lederman, M.D., Chief Executive Officer of Tonix Pharmaceuticals. “TNX-4800 has the potential to fill a major unmet need given there are no FDA approved Lyme disease vaccines or prophylactics and the passive immunity from this long-acting mAb is a novel approach with potential advantages in efficacy and tolerability over vaccines in development that require onerous immunization schedules.4 Lyme disease is the most common vector borne illness in the U.S. and presents a significant and growing public health threat for millions of Americans, particularly since 10-20% of individuals develop long-term consequences from Lyme disease.”

Dr. Lederman continued, “The annual two dose regimen of TNX-4800, with a first dose in the early Spring and a second dose three months later, is expected to provide protection for at least six months, to cover the entire U.S. Lyme disease season. The protection is expected to begin within two days of the first dose. Pending FDA review and approval of the final protocol, we plan to test TNX-4800 as two subcutaneous (SC) injections three months apart. While this will be a Phase 2 study, it has the potential to demonstrate efficacy.”

Tonix intends to enroll adults aged 18 years and older who live in Lyme-endemic regions of the United States and regularly participate in outdoor activities that increase their risk of deer tick bites. The study is designed to evaluate the potential of TNX-4800 as a new preventive option for individuals at elevated risk of Lyme disease.