Acesion Pharma, a biotech company pioneering treatments for atrial fibrillation (AF), the most common cardiac arrhythmia, has announced the enrolment of the first patients in its randomised, double-blind, placebo-controlled, dose finding Phase 2 clinical trial, designed to assess the efficacy and safety of AP31969 in AF patients. The trial will enrol 200 patients across eight European countries, with anticipated completion by Q1 2027.

The primary efficacy endpoint in the trial is AF burden, defined as the percentage of time a participant is in AF. A key safety endpoint is the occurrence of proarrhythmia episodes in the ventricles of the heart. Ventricular proarrhythmia represents the key safety limitation of currently available antiarrhythmic drugs. To enable robust evaluation of these endpoints, participants will receive an implantable loop recorder, allowing for continuous 24/7 cardiac rhythm monitoring.

In 2025, Acesion successfully completed a phase 1 clinical trial of AP31969 in 92 healthy volunteers. The trial included a single ascending dose (SAD) and a multiple ascending dose (MAD) part and was designed to evaluate safety, pharmacokinetics and effects on the QT interval (QTc). Prolongation of QTc is a well-established ECG marker of proarrhythmia risk. AP31969 demonstrated a favourable safety profile and pharmacokinetics suitable for chronic oral administration. Importantly, the trial demonstrated that clinically relevant effects of AP31969 on QTc could be ruled out, supporting a favourable safety profile of AP31969 with respect to proarrhythmia risk – a major concern with current antiarrhythmic drugs.

Anders Gaarsdal Holst, MD, PhD, Chief Executive Officer of Acesion, said: “Advancing our oral lead compound AP31969 into a Phase 2 clinical trial marks an important milestone for Acesion. With the use of implantable loop recorders in the trial, we can precisely estimate AF burden efficacy, as well as understand the risk of proarrhythmia. Being able to robustly understand both the efficacy and the key safety parameter within a therapy class is unusual in a phase 2 cardiovascular trial and, if successful, will greatly de-risk Phase 3 development and accelerate AP31969’s path to becoming the preferred treatment option for the increasing number of patients suffering from AF.”