Tarsus Initiates Phase 2 Calliope Trial for TP-05 Lyme Disease Prevention Amid XDEMVY Growth

Tarsus Pharmaceuticals has moved its lotilaner-based oral prophylactic TP-05 into Phase 2 clinical evaluation, a milestone that extends the company's ectoparasiticide platform well beyond ophthalmology and into tick-borne disease prevention, a therapeutic space with no approved oral prophylactic on the market. The trial, designated Calliope, targets prevention of Lyme disease transmission and is designed to generate a Phase 3-ready package, with topline data expected in the first half of 2027.

For drug development and regulatory leads tracking the lotilaner mechanism, the Calliope design is notable: TP-05 is formulated to kill ticks before potential disease transmission, positioning it as a prophylactic rather than a treatment, a regulatory pathway distinction that will shape the ICH clinical package requirements and endpoint selection heading into any Phase 3 submission. The company has not disclosed trial size, dosing regimen, or the specific tick species in scope, details that will carry weight when the Phase 3-ready package is eventually assessed.

Running in parallel, the Phase 2 trial for TP-04, a lotilaner-based sterile ophthalmic gel for ocular rosacea, continues to progress, also with topline data targeted for the first half of 2027. Both programs share the lotilaner scaffold that underpins XDEMVY (TP-03), the company's approved treatment for Demodex blepharitis, which recorded net product sales of $145.4 million in Q1 2026, an 85% year-over-year increase versus $78.3 million in Q1 2025.

On the global regulatory front, Grand Pharmaceuticals Group, Tarsus's out-license partner in Greater China, secured regulatory approval for XDEMVY in the People's Republic of China, triggering a $15 million milestone payment to Tarsus. European progress is contingent on completing stability work for a preservative-free formulation by end of 2026, while discussions with Japanese regulatory authorities on an approval pathway remain ongoing, two geographies where formulation and dossier decisions made now will determine submission timelines.

Tarsus reaffirmed full-year 2026 XDEMVY net product sales guidance of $670–$700 million, with peak sales potential cited above $2 billion. The company plans to activate approximately 20 new Key Account Leaders by Q3 2026 to deepen utilization within high-opportunity eye care practices.

The Calliope topline readout in H1 2027 will be the first measurable indicator of whether the lotilaner mechanism translates from ophthalmic to systemic prophylactic applications, and whether a Phase 3 package can be assembled on the timeline the company has signaled.

Source: Tarsus Pharmaceuticals via GlobeNewswire, May 6, 2026. Management conference call held May 6, 2026, at 4:30 p.m. ET.