New Oral Drug Trial Aims to Block Lyme Disease Transmission

A new clinical trial has begun testing an oral drug designed to prevent Lyme disease. Tarsus Pharmaceuticals announced that the first participant has received a dose in the Phase 2 study, named Calliope. The trial will assess whether TP-05 (lotilaner), an experimental pill, can stop Lyme transmission by killing infected ticks before they spread the bacteria.

Lyme disease remains a growing health threat, with no FDA-approved medication currently available to prevent it. Over 35 million Americans face a moderate to high risk of infection, and cases have risen sharply in recent years. Calliope is a randomised, double-blind, placebo-controlled trial involving around 700 healthy adults at risk of Lyme disease. Researchers aim to complete enrolment by the 2026 tick season, with initial results due in early 2027. The study follows earlier tests in mice, where TP-05 showed 90% efficacy in preventing Lyme infection, compared to no protection in untreated animals.

A previous Phase 2a trial, called Carpo, found that TP-05 killed over 90% of attached ticks within 24 hours. The drug's rapid action could be key to blocking transmission, as Lyme bacteria typically take 36 to 48 hours to transfer from tick to human.

Lyme disease is now the most common vector-borne illness in the US, with an estimated 300,000 to 400,000 diagnoses each year. Cases have surged by roughly 35% since 2014, partly due to climate change and ticks spreading into new regions. States like Connecticut, New York, and Pennsylvania remain hotspots, but infections are now appearing further south and west.

Bobby Azamian, CEO of Tarsus, called the trial a critical step toward the first FDA-approved oral prophylactic for Lyme. Linden Hu, an immunology professor at Tufts University, highlighted the urgent need for prevention as tick habitats expand and disease rates climb. If successful, TP-05 could become the first on-demand pill to prevent Lyme disease. The trial's results, expected in 2027, will determine whether the drug can offer reliable protection for millions at risk. Currently, no FDA-approved medication exists to stop Lyme infection before it occurs.