Taysha Gene Therapies is a clinical-stage biotech developing gene therapies for central nervous system diseases. Its sole clinical-stage asset is TSHA-102, a one-time gene therapy for Rett syndrome, a rare and progressive neurodevelopmental disease caused by mutations in the MECP2 gene that primarily affects females and causes loss of communication, motor function, and purposeful hand use. There are no approved disease-modifying therapies for Rett syndrome. TSHA-102 delivers a functional copy of the MECP2 gene via a lumbar intrathecal injection — a routine outpatient procedure — using an AAV9 vector. A key design feature is the miRARE element, which regulates MECP2 expression on a cell-by-cell basis to prevent overexpression toxicity. Taysha is running two parallel trials: the REVEAL pivotal trial enrolling 15 females aged 6 to under 22, and the ASPIRE safety trial enrolling younger patients aged 2 to under 4. Phase 1/2 data showed 100% of evaluated patients gained or regained at least one predefined developmental milestone, an outcome with near-zero probability in untreated patients, and no treatment-related serious adverse events have been observed. Taysha holds full global rights to TSHA-102 and has FDA Breakthrough Therapy, RMAT, Fast Track, Orphan Drug, and Rare Pediatric Disease designations. The company generates no revenue and is funded by equity and debt, with roughly $297M in cash as of September 2025. Taysha also has two preclinical programs targeting tauopathies and Fragile X syndrome.