A fourth child has died after developing liver complications on a trial of Astellas Pharma Inc.’s gene therapy for rare neuromuscular disease, after FDA advisers noted the problems on the ASPIRO study in a discussion on gene therapy safety. Last week, Astellas announced that it had stopped dosing on ASPIRO after a safety issue involving liver function emerged in the trial of the gene therapy AT-132, aimed at the life-threatening rare disease X-linked myotubular myopathy.