Taysha Gene Therapies Advances Pivotal Program for TSHA-102 AAV9 Therapy Following Strategic FDA Alignment

DALLAS — January 06, 2026— Taysha Gene Therapies (Nasdaq: TSHA) announced today a significant acceleration in the clinical development of TSHA-102, its investigational AAV9 gene therapy for Rett syndrome. The company confirmed it has dosed the first patient in the REVEAL pivotal trial and reached a critical agreement with the FDA to streamline the path toward a Biologics License Application (BLA) submission for a broad patient population.

Pivotal Trial and Regulatory Breakthroughs

The REVEAL pivotal trial, which began dosing in Q4 2025, is evaluating a high-dose, one-time intrathecal (IT) administration of the AAV therapy in 15 patients aged 6 to 22. This study utilizes a unique primary endpoint: the gain or regain of specific developmental milestones, with each patient serving as their own control.

In a major regulatory win, Taysha reached written alignment with the FDA regarding the ASPIRE safety trial. The agreement allows the company to include just three months of safety data from a small cohort of toddlers (aged 2 to 4) in its BLA. This strategy enables the potential for a broad label covering all patients aged 2 years and older, significantly expanding the therapy’s reach upon approval.

Engineering Safety into AAV Delivery

Rett syndrome is a complex neurological disorder caused by mutations in the MECP2 gene. Because too much MECP2 can be just as toxic as too little, TSHA-102 utilizes a proprietary technology called miRARE. This platform allows the AAV9 vector to regulate gene expression on a cell-by-cell basis, delivering functional protein only where needed while preventing dangerous overexpression.

Upcoming Milestones

The company expects a high-activity year for its AAV pipeline, with several key targets on the horizon:

• Q2 2026: Expected completion of dosing in both the REVEAL pivotal and ASPIRE trials.

• H1 2026: Release of long-term safety and efficacy data from the initial REVEAL Phase 1/2 trials.

• BLA Readiness: The six-month interim analysis from the pivotal trial is expected to serve as the foundation for the upcoming FDA submission.

“With an estimated 15,000 to 20,000 patients affected across the U.S. and Europe, we see a significant opportunity to redefine the treatment paradigm for this devastating disease,” stated Sean P. Nolan, CEO of Taysha.