Tonix says FDA aligns on Phase 2 design for Lyme antibody TNX-4800

Tonix Pharmaceuticals Holding Corp. announced on August 3, 2026 that it had received official minutes from a Type C meeting with the FDA covering the planned adaptive Phase 2 field study of TNX-4800, a human anti-OspA monoclonal antibody intended to prevent Lyme disease in adults in the U.S. The company said alignment with the FDA on key elements of the study design supports a planned Phase 2 start in the first quarter of 2027.¹

According to Zeil Rosenberg, Executive Vice President of Medical at Tonix, the FDA minutes point to agreement on a randomized, placebo-controlled adaptive design that would enroll about 3,300 adult participants across two seasons, with the main efficacy measure being prevention of Lyme disease through six months after the first dose and a secondary measure of prevention through three months.¹ The study's primary safety goal is to assess TNX-4800's safety and tolerability over 52 weeks following dosing.¹ Tonix expects most participants to enroll during the 2028 season, though enrollment could stretch into 2029 if fewer ticks than anticipated carry the disease.¹

Participants would be randomized 1:1 to get either a 450 mg subcutaneous dose of TNX-4800 or placebo, followed by a second dose about three months later.¹ Eligible adults would be 18 or older, living in Lyme-endemic U.S. regions, and at elevated risk of tick exposure through their activities.¹

Rosenberg noted that the company's 2026 efforts have centered on producing investigational supply of TNX-4800, which remains on schedule to reach trial sites by early 2027.¹ Tonix licensed TNX-4800 from UMass Chan Medical School in 2025.¹