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 that it will present new preclinical in vitro data from a head-to-head evaluation of TSHA-102 (scAAV9-miniMeCP2) compared to an analogous ssAAV9 construct with the full-length MECP2 in neuronal cell models. The data will be presented during a poster presentation at the upcoming American Society of Gene and Cell Therapy (ASGCT) Annual Meeting, taking place in Boston from May 11-15, 2026.

TSHA-102 is a scAAV9 gene therapy in clinical evaluation for Rett syndrome that encodes a functional, miniaturized MECP2 transgene, a key design feature that supports enhanced transduction efficiency and stability. Data to be presented are consistent with previously published vector comparisons demonstrating that scAAV9 drives significantly higher MeCP2 protein expression than ssAAV9, which support Taysha's ability to effectively deliver TSHA-102 to the CNS using a minimally invasive lumbar intrathecal (IT) administration. In addition, the data show that the miniMeCP2 protein is functionally comparable to full-length MeCP2 protein across molecular and biochemical functions and exhibits comparable, stable expression in neuronal cells.

"These findings demonstrate that miniMeCP2 protein is functionally comparable to full-length MeCP2 and that the scAAV9 vector enables significantly higher protein expression, delivering up to 30-fold higher MeCP2 than a comparable ssAAV9 construct in neuronal cell models," said Sukumar Nagendran, M.D., President and Head of Research & Development at Taysha. "The enhanced transduction efficiency and improved genomic stability of scAAV9 supports our ability to effectively deliver TSHA-102 to the CNS using a minimally invasive lumbar intrathecal administration. Importantly, the data provide direct mechanistic validation of TSHA-102's differentiated construct design and offer translational support for the early, sustained and deepening functional gains demonstrated following treatment with TSHA-102 in Part A of our REVEAL Phase 1/2 trials. We look forward to reporting longer-term safety and efficacy data from our Part A of REVEAL Phase 1/2 trials later this quarter."