Capsida Biotherapeutics reported that an autopsy identified cerebral edema as the immediate cause of death in a patient dosed in its suspended SYNRGY trial testing an AAV gene therapy for STXBP1 deficiency. The company said pathology did not definitively identify why the edema occurred and that internal reviews found no protocol deviations or manufacturing errors. External experts urged greater transparency on clinical and laboratory findings and access to tissue samples. Capsida said it will continue investigations; the case highlights the continued need for careful safety monitoring and open data sharing when rare, unexpected serious adverse events occur in systemic AAV trials.