Abstract Body (Do not enter title and authors here): Background. PRKAG2 syndrome is an inherited disease caused by mutations in the PRKAG2 gene, which encodes the γ2 regulatory subunit of AMP-activated protein kinase (AMPK). These mutations result in increased AMPK activity leading to aberrant myocardial glycogen deposition. Patients with PRKAG2 syndrome can develop cardiac hypertrophy, ventricular pre-excitation, supraventricular arrhythmias and conduction system disease, all of which increase the risk of sudden cardiac death. Some patients develop progressive heart failure necessitating heart transplantation. Current treatments include standard medications for heart failure and pacemaker/ICD implantation for arrhythmias. However, there is a significant need to treat the underlying causes of PRKAG2 syndrome. Small interfering RNA (siRNA) oligonucleotides present a promising therapeutic approach by reducing mutant PRKAG2 mRNA levels, thereby lowering AMPK activity.

Hypothesis. Antibody oligonucleotide conjugates (AOCs) can be designed to target PRKAG2 mRNA to treat PRKAG2 syndrome.

Aims. To investigate the tolerability and efficacy of an AOC targeting PRKAG2 mRNA in mice and non-human primates (NHPs).

Methods. iPSC-derived cardiomyocytes were used to screen and identify a potent siRNA against PRKAG2. The lead siRNA was conjugated to an anti-TfR1 monoclonal antibody to create AOC 1072 for targeted cardiac delivery and was subsequently administered to mice and NHPs.

Results. In vitro screening identified an siRNA with an EC50 <10 pM and a maximum PRKAG2 mRNA reduction >90%. A single, IV injection of the mouse surrogate of AOC 1072 at 1 mg/kg (siRNA component) resulted in a potent and durable myocardial Prkag2 mRNA reduction in mice, with about 75% and 50% reduction observed at 2 and 6 months, respectively. AOC treatment reduced glycogen accumulation in the skeletal muscle of mice expressing the Prkag2-R528G disease variant. A single IV administration of AOC 1072 at 3 mg/kg (siRNA component) resulted in about 85% reduction of cardiac PRKAG2 mRNA in NHPs at 28 days, with no adverse effects (ECG or heart weight).

Conclusions. Our data suggests AOC technology can be used efficiently to deliver siRNA to the heart. This precision cardiology treatment can significantly reduce PRKAG2 mRNA expression, offering a promising therapeutic approach for PRKAG2 syndrome, a currently incurable genetic condition with very limited treatment options.