Shattering Expectations: Gene Therapy Ignites Hope for Rett Syndrome, Pivotal Trial Looms

Unprecedented Progress: Taysha Gene Therapies announces FDA alignment for a pivotal trial of TSHA-102 in Rett syndrome, fueled by groundbreaking clinical data.
100% Response: Astonishingly, every child and adult treated with TSHA-102 in early trials regained critical daily life functions, defying the bleak natural progression of the disease.
New Era Dawns: This breakthrough could redefine treatment for Rett syndrome, offering a path to a potentially transformative therapy for thousands.

DALLAS – May 28, 2025 – In a stunning development that pierces through the gloom of Rett syndrome, Taysha Gene Therapies (Nasdaq: TSHA) today unveiled plans for a pivotal Part B trial of its gene therapy candidate, TSHA-102. This decisive step, made with the U.S. Food and Drug Administration's (FDA) green light, follows electrifying positive clinical data where hope became tangible.

Rett syndrome, a severe neurodevelopmental disorder, typically steals developmental milestones from children, with natural history data grimly showing that regaining them after age six is "highly improbable"^{2, 6}. Yet, Taysha's REVEAL trials tell a different story: a staggering 100% of pediatric, adolescent, and adult patients treated with TSHA-102 gained or regained one or more developmental milestones vital for daily living.

"It is quite striking that we observed a 100% responder rate," declared Sean P. Nolan, Taysha's Chairman and CEO. "We believe this objective and clinically meaningful primary endpoint has the potential to redefine treatment expectations and expand the possibilities of gene therapy for patients with Rett syndrome."

TSHA-102, a one-time AAV9-based gene therapy, aims to correct the genetic root cause of Rett by delivering a functional MECP2 gene, utilizing novel miRARE technology to ensure regulated protein expression^{3, 4}. The alignment with the FDA, supported by International Rett Syndrome Foundation (IRSF) natural history data, "validates these important findings...and strengthen our conviction in the transformative potential of TSHA-102," Nolan added.

With plans to submit the pivotal trial protocol this quarter and initiate the program in Q3 2025, Taysha is on an "efficient and expeditious path to potentially deliver TSHA-102 to patients and families suffering from this devastating disease." This progress, built on collaborative research and patient dedication, signals a potential paradigm shift from mere symptom management to a disease-modifying intervention for the estimated 15,000 to 20,000 patients in the U.S., EU, and U.K.⁶. Further details are available in a Current Report on Form 8-K on the SEC’s website at www.sec.gov.

Shattering Expectations: Gene Therapy Ignites Hope for Rett Syndrome, Pivotal Trial Looms

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