The primary objectives of this study are to evaluate the safety of a single intrathecal (IT) dose of TSHA-102 in females with typical Rett syndrome, to select the TSHA-102 dose with the best benefit/risk profile based on the totality of safety and efficacy data and to evaluate the efficacy and safety of TSHA-102 at the selected dose.
Females between the ages of 12 and <22 in Part A (closed) and females between the ages of 6 and <22 in Part B (pivotal cohort).
Participant has a clinical diagnosis of classic/typical Rett syndrome with a documented pathogenic mutation of the methyl-CpG-binding protein 2 (MECP2) gene that results in loss of gene function.
Participants must be willing to receive blood or blood products for the treatment of an AE if medically needed.
Participants and parent/caregiver must agree to reside within easy access to the study site prior to the baseline visit and at least 3 months after TSHA-102 treatment
Participant has another neurodevelopmental disorder independent of the MECP2 loss-of-function mutation, or any other genetic syndrome with a progressive course.
Participant has a history of brain injury that causes neurological problems or had grossly abnormal psychomotor development in the first 6 months of life.
Participant has a diagnosis of atypical Rett syndrome or a MECP2 gene mutation that does not cause Rett syndrome.
Participant requires invasive ventilatory support.