Tarsus Initiates Phase 2 Calliope Trial Advances Oral Tick-Killing Therapy TP-05 In Lyme Disease Prevention

Tarsus Pharmaceuticals, Inc. announced that the first participant has been dosed in its Phase 2 Calliope trial evaluating TP-05 (lotilaner), an investigational oral therapy to prevent Lyme disease. The therapy works by killing infected ticks before they can transmit the disease to humans.

The Calliope study is a randomised, double-blind, placebo-controlled trial involving approximately 700 healthy adults at risk of Lyme disease across endemic regions in the United States. The trial will assess the safety, tolerability, and pharmacokinetics of TP-05, with enrollment expected to be completed during the 2026 tick season and topline results anticipated in the first half of 2027.

“For decades, Lyme disease management has focused on treating infection after it occurs,” said Bobby Azamian, M.D., PhD, 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. 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.”

Currently, there are no FDA-approved pharmacological options for preventing Lyme disease, which is caused by Borrelia burgdorferi and transmitted by ticks. With tens of millions of Americans at risk and hundreds of thousands of cases reported annually, there remains a significant unmet need for preventive solutions.

“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 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. New prophylactic approaches with the potential to help reduce the risk of infection could play an important role in addressing this growing threat.”

The trial builds on earlier Phase 2a findings from the Carpo study, in which a single dose of TP-05 demonstrated strong efficacy against ticks, with over 90% mortality within 24 hours, compared with minimal effect in the placebo group. Preclinical studies have also shown promising results, supporting TP-05's potential as a preventive therapy.