Capsida Biotherapeutics said it still does not know what caused a child’s death in a gene therapy trial of CAP-002, which delivered genes into the brain. The company said its investigation has been hindered because the hospital where the study was conducted declined to share tissue samples from the autopsy. The report underscores the investigative bottlenecks that can slow safety inquiries in neurotropic gene therapies, particularly those aimed at crossing the blood-brain barrier. Without tissue samples, teams may be limited in linking observed clinical events to vector biology, transgene expression, immune responses or other causative mechanisms. For the gene-therapy sector, the update adds pressure to ensure standardized autopsy and data-sharing pathways, while regulators and sponsors coordinate on safety reporting and risk mitigation. It also highlights the continued scrutiny facing brain-penetrant AAV programs as the field expands into more indications. The next milestone will be what evidence Capsida can produce despite the missing samples, and how that evidence aligns with FDA expectations for continued development and safety monitoring.