Taysha Gene Therapies is currently investigating TSHA-102, an adeno-associated virus (AAV) vector-based gene therapy, for the treatment of Rett syndrome in two Phase 1/2 clinical trials: the REVEAL adolescent and adult trial (NCT05606614) and the REVEAL Pediatric Study (NCT06152237). These trials aim to assess the safety and efficacy of TSHA-102 in addressing this challenging neurodevelopmental disorder.
TSHA-102: A Novel Approach to Rett Syndrome
TSHA-102 is administered intrathecally (IT) and delivers a copy of miniMECP2, a truncated version of the MECP2 gene, via an AAV9 vector. The gene therapy also incorporates Taysha's miRNA-Responsive Auto-Regulatory Element (miRARE) platform, designed to enable regulation of cellular expression for both endogenous and exogenous MECP2. This regulatory mechanism is crucial for preventing overexpression, which can lead to toxicity.
REVEAL Adolescent and Adult Clinical Trial Details
The REVEAL adolescent and adult trial, initiated on March 6, 2023, is a dose escalation and dose expansion study expected to enroll approximately 18 patients. The trial includes two dose level cohorts and is currently recruiting at sites in Quebec, Canada, and Chicago, Illinois, with additional sites planned in other locations in the US. The primary endpoints include the proportion of participants experiencing treatment-emergent adverse events (TEAEs) and serious adverse events (SAEs), as well as changes in Clinical Global Impressions-Improvement (CGI-I) scale adapted for Rett syndrome, Revised Motor Behavior Assessment (R-MBA), and Rett Syndrome Hand Function Scale (RSHFS) scores from baseline to 52 weeks post-treatment. Secondary endpoints include changes in CGI-I scale, seizure frequency, adaptive behavior measured via Vineland-3, and quantitative EEG findings. The study includes women and girls aged 12 years and older clinically diagnosed with classical/typical Rett syndrome with a loss-of-function mutation in the MECP2 gene.
REVEAL Pediatric Study Design
The REVEAL Pediatric Study, initiated on December 12, 2023, follows a similar dose escalation and dose expansion design, evaluating TSHA-102 in a lower and higher dose cohort. This trial expects to enroll approximately 20 participants. The primary endpoint for the REVEAL Pediatric Study is the incidence of TEAEs and SAEs. Secondary endpoints include changes in CGI-I status, R-MBA status, Rett Syndrome Behavior Questionnaire status, Clinical Global Impressions-Severity status, quantitative EEG findings, and the percent change in monthly countable seizure frequency. The study is open to girls aged 5 to 8 years who have been clinically diagnosed with classical/typical Rett syndrome with a loss-of-function mutation in MECP2. Participants must have received all relevant locally-required vaccines within 42 days or more of starting the study’s immunosuppression regimen.
Early Clinical Observations
In June 2024, Taysha announced early results from the first two pediatric patients treated in the REVEAL Pediatric Study, along with updated results from the adolescent and adult clinical trial. According to Colleen Buhrfiend, MD, an assistant professor of pediatrics at RUSH University Medical Center, both pediatric patients with different genotypes and disease severity experienced challenging side effects related to immunosuppressant treatment but showed a well-tolerated safety profile with no SAEs or dose-limiting toxicities related to TSHA-102 as of week 22 and week 11 post-treatment for the first and second pediatric patient, respectively, as well as some initial improvements across multiple clinical domains and early evidence of new developmental gains.
