Capsida Reports Death of Patient in STXBP1 Gene Therapy Trial

Rare Daily Staff

Capsida Biotherapeutics said the first patient treated in a phase 1/2a clinical trial of its experimental gene therapy for the treatment of developmental and epileptic encephalopathy STXBP1-related disorders has died.

In a letter to the STXBP1 community posted on the company’s website, Capsida said it has voluntarily paused the CAP-002 SYNRGY study while it determines the root cause of the patient’s death. The company said it has notified the U.S. Food and Drug Administration and will provide a full report to the agency in compliance with regulations.

Capsida said that once the work is complete, it will assess the next steps with respect to the program.

Syntaxin-binding protein 1 developmental and epileptic encephalopathy (STXBP1-DEE) is associated with early-onset seizures, severe developmental delay and intellectual disability, motor abnormalities, and a risk of sudden unexpected death in epilepsy (SUDEP). It is caused by mutations to the STXBP1 gene. The STXBP1 protein is present in every neuron and is essential for normal neurotransmission. There are no approved treatments for STXBP1-DEE.

CAP-002 uses Capsida’s proprietary engineered capsids and optimized cargo. In nonhuman primate studies to date, CAP-002 has established transduction of more than 70 percent of neurons across critical brain areas, while simultaneously de-targeting the liver and dorsal root ganglia. This brain-wide expression of STXBP1 has the potential to correct seizures, developmental disabilities, and motor abnormalities after a single IV infusion. CAP-002 has received FDA orphan drug designation.