TSHA-102 Rett 12-Month Part A Data Reinforce Durability; Part B Fully Enrolled

Research evidence excerpt

TSHA-102 Rett 12-Month Part A Data Reinforce Durability; Part B Fully Enrolled

C O M PA N Y N O T E

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• Part B Cohort Completed Dosing in June. TSHA also announced that 17 patients were

enrolled in Part B and completed dosing this past month. The upcoming Part A 12-month data

update should serve as a direct read-through to Part B, as the two studies are comparable

in methodology, both requiring video-evidence of gain/regain from baseline evaluated by

multiple independent external raters with the same rating criteria. The key difference in Part

B is that baseline video assessments are formally structured and kept blinded until the 6-

month review, when external raters adjudicate all milestones together in a blinded fashion.

The company also reports that three patients in ASPIRE will complete dosing this month and

a fourth patient is expected to receive TSHA-102 in July. Based on the Part A update, TSHA

is encouraged that it could file on interim 6-month Part B data, and plans to pool data across

both cohorts to support long-term durability. The company believes it will reach 6 months for

all pts in Part B in Dec '26, after which it will schedule a meeting with the FDA for 1Q27.

Following that meeting, the company plans to disclose topline results in 1H27 after receiving

FDA meeting minutes. We expect an update in late 1Q/early 2Q27. In the near-term TSHA

expects to complete PPQ in 4Q which would prove comparability of Part B CMC to Part A

CMC and enable TSHA to use Part A evidence in the regulatory submission.

• Patient/Caregiver Feedback Is Positive: The company also provided anecdotes from

patients/caregivers post TSHA-102, with several caregivers expressing positive feedback that

they are able to verbally communicate with their child.