Audentes Therapeutics, Inc. announced that a third study patient has passed away in the ASPIRO clinical trial evaluating AT132 in patients with X-linked Myotubular Myopathy (XLMTM), which is a serious, life-threatening neuromuscular disease characterized by extreme muscle weakness, respiratory failure, and early death. Preliminary findings indicate that the immediate cause of death was gastrointestinal bleeding. This patient was one of three study patients previously disclosed to have received AT132 at the dose of 3x1014 vg/kg who began to demonstrate signs of liver dysfunction within 3 to 4 weeks after dosing. All three patients demonstrated evidence of pre-existing hepatobiliary disease. More than 50% of patients enrolled in the ASPIRO trial to date show evidence of pre-existing hepatobiliary disease, but it has not been associated with similar progressive liver dysfunction in any of the patients who received AT132 at the 1x1014 vg/kg dose nor in the other patients who received the 3x1014 vg/kg dose. To date, 23 ASPIRO patients have received AT132: six at the 1x1014 vg/kg dose and 17 at the 3x1014 vg/kg dose. Although the ASPIRO study is currently on clinical hold, there are no other patients in the study known to be currently experiencing similar liver dysfunction. Audentes, together with the ASPIRO investigatorsand independent Data Monitoring Committee, continue to closely monitor all patients enrolled in the study. Additionally, Audentes’ investigation regarding why these three patients developed progressive liver dysfunction is ongoing.