Shares of Lexeo Therapeutics (NASDAQ:LXEO) dropped about 17% on Monday after the company published interim Phase I/II results for its PKP2 gene therapy candidate, LX2020, being developed for PKP2-associated arrhythmogenic cardiomyopathy.
The clinical-stage genetic medicine company said LX2020 was generally well tolerated in ten treated participants, with no clinically meaningful complement activation reported. The data showed dose-related increases in PKP2 protein expression, averaging a 93% rise in the low-dose group and a 162% increase among high-dose participants.
Lexeo noted that arrhythmia burden was stable or improved in most patients, with dose-dependent effects observed in non-sustained ventricular tachycardia and premature ventricular contractions. However, the market reaction suggested investors viewed the interim results as falling short of expectations.
Data from the HEROIC-PKP2 study indicated that non-sustained ventricular tachycardia was reduced or stabilized in the majority of participants, including a mean improvement of 22% in the high-dose cohorts at the most recent assessment. Premature ventricular contractions were also reduced or stabilized in most patients, with high-dose groups showing an average improvement of 14%.
On the safety side, five high-dose participants experienced elevated liver function tests, which were successfully managed with the reintroduction of steroids. In addition, one Grade 3 serious adverse event — sustained ventricular tachycardia — occurred three months after dosing in a single high-dose participant.
Lexeo completed patient enrollment in the HEROIC-PKP2 trial during the fourth quarter of 2025. The company expects to report 12-month data for all high-dose participants in the fourth quarter of 2026 and plans to engage with regulators during 2026.