Tarsus Pharmaceuticals Initiates Phase 2 Trial for First Oral Lyme Disease Prevention Therapy
Key Insights
Tarsus Pharmaceuticals has dosed the first participant in the Phase 2 Calliope trial evaluating TP-05 (lotilaner), a novel oral tablet designed to prevent Lyme disease (search) by killing infected ticks before transmission.
The randomized, double-blind, placebo-controlled trial will enroll approximately 700 healthy adults at risk for Lyme disease (search) across endemic U.S. regions, with topline results expected in the first half of 2027.
Previous Phase 2a data showed TP-05 achieved over 90% tick kill rates within 24 hours compared to 5% for placebo, representing a potential paradigm shift from treatment to prevention for the most common vector-borne disease in the United States.
Tarsus Pharmaceuticals has initiated dosing in its Phase 2 Calliope trial, marking a significant milestone in the development of what could become the first FDA-approved oral prophylactic therapy for Lyme disease (search) prevention. The company announced that the first participant has been dosed with TP-05 (lotilaner), an investigational oral tablet designed to kill Lyme-infected ticks before disease transmission occurs.
Novel Prevention Approach Targets Disease Transmission
The Calliope trial represents a pioneering approach to Lyme disease (search) management, shifting focus from post-infection treatment to prevention. "For decades, Lyme disease management has focused on treating infection after it occurs," said Bobby Azamian, M.D., Ph.D., Chief Executive Officer and Chairman of Tarsus. "We believe there is an opportunity to fundamentally shift that paradigm toward prevention by targeting the ticks that transmit the disease."
TP-05 is believed to be the only non-vaccine, drug-based prophylactic in development designed to kill ticks to potentially prevent Lyme disease (search) transmission. The investigational therapy is an oral systemic formulation of lotilaner, the same active ingredient used in Tarsus's FDA-approved eye treatment XDEMVY.
Phase 2 Trial Design and Timeline
The Calliope trial is a randomized, double-blind, placebo-controlled Phase 2 study evaluating the safety, tolerability and pharmacokinetics of orally administered TP-05 in approximately 700 healthy adults at risk for Lyme disease (search) across endemic regions of the United States. Tarsus plans to complete enrollment during the 2026 tick season, with topline results expected in the first half of 2027.
The trial design was informed by promising results from the Phase 2a Carpo study, a randomized, double-blind, placebo-controlled, proof-of-concept "tick kill" study. In that earlier trial, a single dose of TP-05 demonstrated statistically significant tick mortality versus placebo at both Day 1 and Day 30. Tick kill rates exceeded 90% within 24 hours of attachment after the Day 1 tick challenge compared to only 5% for placebo (p<0.001), and TP-05 was generally well tolerated.
Addressing Growing Public Health Challenge
The development comes as Lyme disease (search) presents an increasingly urgent public health challenge. According to recent market research cited by Tarsus, more than 35 million Americans are considered to be at moderate to high risk of contracting Lyme disease, and an estimated 300,000 to 400,000 people are diagnosed annually.
"With climate change and the expanding geographic range of ticks infected with human pathogens contributing to a growing burden of tick-borne illnesses, Lyme disease (search) is becoming an increasingly urgent public health challenge," said Linden Hu, M.D., the Paul and Elaine Chervinsky Professor of Immunology at Tufts University School of Medicine. "Tick bites and early symptoms are often missed, leading to missed diagnoses or delayed treatment, increasing the risk of serious long-term complications."
Significant Unmet Medical Need
Currently, there are no FDA-approved pharmacological prophylactic options for Lyme disease (search), the most common vector-borne disease in the United States. The disease is caused by Borrelia burgdorferi (search) infection and transmitted through the bite of infected ticks. Early signs of Lyme disease are often overlooked or misdiagnosed, and left untreated, the condition can potentially cause severe, often debilitating symptoms with permanent and irreversible damage.
The disease can result in inflammation, nerve, joint and muscle pain and swelling, numbness, shortness of breath and, in severe cases, neurological complications such as facial palsy, vision issues and meningitis, including severe headaches and neck stiffness, as well as cardiac complications. Data from the Centers for Disease Control and Prevention show that the risk of Lyme disease (search) is spreading to new geographical areas, creating significant need for prophylactic solutions.
Preclinical Efficacy Data
Supporting the clinical development program, preclinical pilot studies in mice evaluating TP-05 for the prevention of Lyme disease (search) demonstrated 90% efficacy versus 0% in control mice, providing additional evidence for the therapy's potential effectiveness.
The Calliope trial represents an important step in developing what could potentially be the first FDA-approved on-demand oral prophylactic option designed to help prevent Lyme disease (search), addressing a critical gap in current prevention strategies for this growing public health threat.