Tarsus Doses First Participant in Calliope, A Phase 2 Clinical Trial of TP-05 (lotilaner), a Novel Investigational Oral Tablet for the Potential Prevention of Lyme Disease

IRVINE, Calif., March 31, 2026 (GLOBE NEWSWIRE) -- Tarsus Pharmaceuticals, Inc. (NASDAQ: TARS) today announced that the first participant has been dosed in the Phase 2 clinical trial (Calliope) evaluating TP-05 (lotilaner), a novel investigational oral therapy designed to potentially prevent Lyme disease by killing Lyme-infected ticks before disease transmission occurs.

Calliope is a randomized, double-blind, placebo-controlled Phase 2 trial evaluating the safety, tolerability and pharmacokinetics of orally administered TP-05 in approximately 700 healthy adults at risk for Lyme disease 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.

“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. 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.”

“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.”

There are currently no U.S. Food and Drug Administration (FDA)-approved pharmacological prophylactic options for Lyme disease, the most common vector-borne disease in the United States. Lyme disease is caused by Borrelia burgdorferi infection and transmitted through the bite of infected ticks. According to recent market research, more than 35 million Americans are considered to be at moderate to high risk of contracting Lyme disease, and an estimated 300,000 – 400,000 people are diagnosed annually.

The Calliope trial design was informed by the Phase 2a Carpo randomized, double-blind, placebo-controlled, proof-of-concept “tick kill” study, in which 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