SOUTH SAN FRANCISCO, Calif., May 15, 2026
Tenaya Therapeutics reported encouraging interim Phase 1b/2 clinical data for TN-401, its investigational gene therapy targeting PKP2-associated arrhythmogenic right ventricular cardiomyopathy (ARVC), demonstrating meaningful reductions in arrhythmia burden and a favorable safety profile across all treated patients. The data, presented at the 2026 Annual Meeting of the American Society of Gene and Cell Therapy (ASGCT), strengthen the growing potential of one-time gene therapies to address the underlying genetic drivers of inherited heart diseases rather than only treating symptoms.
TN-401 Demonstrates Consistent Reduction in Arrhythmias
The ongoing RIDGE™-1 Phase 1b/2 trial evaluated TN-401 in adults with ARVC caused by mutations in the PKP2 gene, a leading genetic cause of the disease. According to interim findings from the first six patients treated, all participants experienced clinically meaningful decreases in premature ventricular contractions (PVCs), a major indicator of dangerous heart rhythm instability.
The study reported an average 64% reduction in daily PVC burden, with some patients achieving reductions exceeding 80%. Two patients with high baseline levels of non-sustained ventricular tachycardia (NSVT) showed dramatic improvements, including one patient whose NSVT episodes dropped from 78 counts per 24 hours to zero by Week 52.
Researchers noted that TN-401 was well tolerated at both tested dose levels — 3E13 vg/kg and 6E13 vg/kg — with no dose-limiting toxicities, no treatment-related ventricular arrhythmias, and no cases of thrombotic microangiopathy observed during the study period. Importantly, all treated patients successfully tapered off immunosuppressive therapy while remaining on study.
Biopsy Data Confirm Gene Therapy Activity in Heart Cells
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A major highlight of the update was the biopsy evidence confirming successful delivery and activity of the gene therapy within heart muscle cells. Post-dose cardiac tissue samples showed measurable TN-401 DNA and messenger RNA expression, indicating active gene transfer and protein production inside cardiomyocytes.The findings support TN-401’s mechanism of action, which aims to restore proper expression of the PKP2 protein, a key structural component responsible for maintaining electrical and physical connections between heart muscle cells.
PKP2-associated ARVC is a serious inherited cardiomyopathy in which damaged cardiac tissue becomes replaced by fibrofatty tissue, increasing the risk of life-threatening ventricular arrhythmias and sudden cardiac death. Existing therapies, including implantable cardioverter-defibrillators (ICDs), anti-arrhythmic drugs, and catheter ablation procedures, do not correct the underlying genetic defect.According to Tenaya investigators, the observed improvements in electrical stability suggest TN-401 may potentially modify disease progression rather than simply manage symptoms.
EMA Grants PRIME Designation to TN-401
In addition to the clinical update, Tenaya announced that the European Medicines Agency (EMA) granted PRIME designation to TN-401. The designation is intended for therapies addressing major unmet medical needs and provides enhanced regulatory support designed to accelerate development and review timelines.The RIDGE-1 study is currently enrolling patients in the United States and United Kingdom, with future expansion cohorts planned. Tenaya stated that additional data from newly dosed patients will be included in upcoming clinical updates later in 2026.
The company believes TN-401 could become a transformative treatment option for the estimated 70,000+ individuals in the United States living with PKP2-associated ARVC, a condition often diagnosed before age 40 and strongly associated with sudden cardiac arrest risk. As the cardiovascular gene therapy field continues to advance, the TN-401 data add to growing evidence that precision genetic medicines may eventually redefine treatment approaches for inherited cardiac disorders.
Source: Tenaya Therapeutics press release
