Capsida Biotherapeutics Receives FDA Clearance for IND Application for CAP-002 Gene Therapy for STXBP1-DEE

THOUSAND OAKS, Calif. – May 13, 2025 – Capsida Biotherapeutics today announced that the U.S. Food and Drug Administration (FDA) has cleared its Investigational New Drug (IND) application for CAP-002, a first-in-class, intravenously (IV) administered gene therapy entering clinical trials for syntaxin-binding protein 1 developmental and epileptic encephalopathy (STXBP1-DEE).

CAP-002 marks a significant advancement as the first program to enter human trials utilizing an IV-administered, blood-brain barrier-crossing engineered capsid that is also designed to avoid off-target tissues like the liver and dorsal root ganglia (DRG). This innovative therapy is enabled by Capsida’s proprietary engineered capsids and optimized cargo.

STXBP1-DEE is a severe neurological disorder estimated to affect up to one in 26,000 births globally, resulting in approximately 5,000 pediatric patients in the U.S. and Europe. The STXBP1 protein is crucial for normal neurotransmission, and mutations in the STXBP1 gene lead to early-onset seizures, severe developmental delay and intellectual disability, motor abnormalities, and an increased risk of sudden unexpected death in epilepsy (SUDEP). Currently, there are no approved treatments for this devastating condition.

Charlene Son Rigby, STXBP1 Foundation President and Cofounder, emphasized the urgent need for targeted therapies to improve the lives of affected children and families, noting that traditional AAVs like AAV9 have not been able to achieve the widespread neuronal transduction necessary to modify the disease.

However, Capsida’s CAP-002 has demonstrated remarkable results in non-human primate (NHP) studies, achieving transduction of over 70% of neurons across critical brain areas while simultaneously avoiding the liver and DRGs. This extensive brain-wide expression of STXBP1 holds the potential to correct seizures, developmental disabilities, and motor abnormalities following a single IV infusion. The NHP Good Laboratory Practice (GLP) toxicology study has shown a well-tolerated safety profile with no adverse histopathology. CAP-002 received Orphan Drug Designation (ODD) from the FDA in October 2024.

Capsida is now initiating study start-up activities for the SYNRGY Phase 1/2a clinical trial, with the first patient expected to be dosed in the third quarter of this year.

Ingo Helbig, M.D., Pediatric Neurologist and Clinical Director at the Center for Epilepsy and Neurodevelopmental Disorders (ENDD) at Children’s Hospital of Philadelphia (CHOP), highlighted CAP-002 as the first potentially disease-modifying treatment for STXBP1-DEE and expressed excitement about participating in the SYNRGY clinical trial.

Swati Tole, M.D., Chief Medical Officer of Capsida, underscored the significance of the FDA clearance for the STXBP1 community and the broader field of genetic medicine, expressing anticipation for the initiation of the SYNRGY trial and the potential to deliver the first targeted therapy for STXBP1-DEE.