Taysha Gene Therapies Inc (NASDAQ:TSHA) shares rose 3.6% in premarket trading on Monday after the company announced the completion of patient dosing in its pivotal Rett syndrome study and released updated long-term clinical data for its lead gene therapy candidate, TSHA-102.
The biotechnology company said the latest results continue to support the therapy’s safety profile and demonstrate sustained functional improvements in treated patients.
Pivotal REVEAL Trial Reaches Key Milestone
Taysha confirmed that all 17 patients enrolled in the pivotal portion of its REVEAL study have now received treatment with TSHA-102.
The trial is evaluating the gene therapy as a treatment for Rett syndrome, a rare neurodevelopmental disorder.
The company expects to report topline findings from a six-month interim analysis during the first half of 2027 and anticipates receiving feedback from the U.S. Food and Drug Administration regarding the Biologics License Application (BLA) pathway during the same period.
Safety Profile Remains Encouraging
As of the June 2026 data cutoff, TSHA-102 continued to demonstrate a favourable safety profile across both the Phase 1/2 and pivotal portions of the REVEAL programme.
The company reported no treatment-related serious adverse events and no dose-limiting toxicities among the 29 patients treated to date.
Management said the results reinforce confidence in the therapy as development progresses toward potential regulatory submission.
Patients Show Meaningful Functional Improvements
Data from the REVEAL Part A study showed that all patients aged between six and 21 years either gained or regained at least one developmental milestone within 12 months of treatment.
Across the 12 patients followed for at least one year, researchers recorded a total of 310 functional improvements, averaging approximately 26 gains per patient.
These included 31 developmental milestones as well as 279 additional improvements in skills and day-to-day functioning.
Benefits Continue to Deepen Over Time
According to the company, longer-term follow-up suggests that the treatment effect continues to strengthen beyond the initial months following administration.
Functional gains accumulated across multiple core disease areas, with developmental milestone improvements increasing by 69% between six and 12 months after treatment and by 94% between six months and the longest follow-up periods reported.
The findings suggest TSHA-102 may deliver durable benefits that continue to evolve over time.
Additional Trial Progress Supports Regulatory Plans
Taysha also announced progress in its ASPIRE study, which enrolled four patients aged between two and five years and exceeded its original enrollment target.
The company expects to complete dosing in the ASPIRE trial during July 2026.
In addition, Taysha anticipates completing the Process Performance Qualification campaign required to support a future BLA submission for TSHA-102 in the fourth quarter of 2026.
The milestones are expected to support the company’s broader regulatory strategy as it advances the programme toward potential approval.