Capsida Biotherapeutics reported that an autopsy confirmed cerebral edema as the cause of death in a patient treated in its suspended SYNRGY trial of CAP‑002 (AAV gene therapy for STXBP1). The company said its internal review found no clinical trial errors and that manufacturing, handling and dosing records were in order, but it acknowledged the underlying trigger for the edema remains undetermined. External experts urged transparency and access to tissue and lab data; Capsida said it will continue investigations and has requested patient tissue samples collected at autopsy. The trial has remained on hold since the fatal event in late 2025.