Taysha Gene Therapies Announces FDA Breakthrough Therapy Designation and Provides Positive Regulatory Update on TSHA-102 in Rett Syndrome

Breakthrough Therapy designation granted based on FDA’s review of available clinical evidence of safety and efficacy from all 12 patients treated in Part A of the REVEAL Phase 1/2 trials

Finalized FDA alignment on REVEAL pivotal trial protocol and SAP following resolution of remaining clinical and statistical queries to IND application amendment; on track to begin patient enrollment in Q4 2025

Key pivotal trial design elements remain unchanged, including 6-month interim analysis to potentially expedite BLA submission based on the rigorous developmental milestone evaluation in Part A showing an unprecedented response rate at 6 months post-TSHA-102 that deepened over time

DALLAS, Oct. 02, 2025 (GLOBE NEWSWIRE) -- Taysha Gene Therapies, Inc. (Nasdaq: TSHA) (Taysha or the Company), a clinical-stage biotechnology company focused on advancing adeno-associated virus (AAV)-based gene therapies for severe monogenic diseases of the central nervous system (CNS), today announced the U.S. Food and Drug Administration (FDA) has granted Breakthrough Therapy designation to TSHA-102, an intrathecally delivered AAV9 gene therapy with disease modifying potential, for the treatment of Rett syndrome. Additionally, the Company announced that it has finalized alignment with the FDA on the REVEAL pivotal trial protocol and statistical analysis plan (SAP) that are intended to support the planned Biologics License Application (BLA) submission for TSHA-102, following the resolution of remaining clinical and statistical queries.

Breakthrough Therapy designation and finalized FDA alignment on the pivotal trial protocol and SAP were based on the FDA’s review of positive clinical evidence from Part A of the REVEAL Phase 1/2 adolescent/adult and pediatric trials.

Breakthrough Therapy Designation Granted by FDA for TSHA-102 in Rett Syndrome

The FDA grants Breakthrough Therapy designation to expedite the development and regulatory review of an investigational therapy intended to treat a serious condition. A drug is eligible for this designation if it demonstrates preliminary clinical evidence of substantial improvement over available treatments in one or more clinically significant endpoints.

Clinical evidence supporting Breakthrough Therapy designation for TSHA-102 included previously disclosed Part A REVEAL clinical data demonstrating a generally well-tolerated safety profile and a 100% response rate post-TSHA-102 (May 2025 data cutoff) for the pivotal trial primary endpoint of the gain/regain of ≥ one defined developmental milestone, with <6.7% likelihood of being achieved without treatment based on natural history data. These findings were corroborated by dose-dependent improvements in multiple outcome measures, including Revised Motor Behavior Assessment (R-MBA) and Clinician Global Impression – Improvement (CGI-I).