Safety and Efficacy of TSHA-102 in Adolescent and Adult Females with Rett Syndrome (REVEAL Adult Study)

Inclusion Criteria:

• Participant has a clinical diagnosis of classical/typical Rett syndrome with adocumented pathogenic mutation of the methyl-CpG-binding protein 2 (MECP2) gene thatresults in loss of function.

• Participants must be willing to receive blood or blood products for the treatment ofan AE if medically needed.

Exclusion Criteria:

• Participant has another neurodevelopmental disorder independent of the MECP2loss-of-function mutation, or any other genetic syndrome with a progressive course.

• Participant has a history of brain injury that causes neurological problems.

• Participant had grossly abnormal psychomotor development in the first 6 months oflife.

• Participant has a diagnosis of atypical Rett syndrome.

• Participant has a MECP2 mutation that does not cause Rett syndrome.

• Participant requires invasive ventilatory support.

• Participant has contraindications for IT administration of TSHA-102 or lumbarpuncture procedure, or other medical conditions, or contraindications to anymedications required for IT administration.

• Participant has uncontrolled seizures or a history of status epilepticus within the 3 months prior to enrollment.