Taysha Gene Therapies (TSHA) FDA Approvals

Taysha Gene Therapies' Drug in the FDA Approval Process

This section highlights FDA-related milestones and regulatory updates for drugs developed by Taysha Gene Therapies (TSHA). Over the past two years, Taysha Gene Therapies has reported clinical trial outcomes, regulatory submissions, approvals, and other FDA events for drugs and therapies such as TSHA-102. For definitions of regulatory abbreviations such as NDA, BLA, or PDUFA, see the event status legend.

TSHA-102 FDA Regulatory Timeline and Events

TSHA-102 is a drug developed by Taysha Gene Therapies for the following indication: Rett Syndrome. This drug is under review by the U.S. Food and Drug Administration (FDA). Below is a timeline of key regulatory milestones for this therapy.

Preclinical Data - April 27,2026

• Drug: TSHA-102
• Announced Date: April 27, 2026
• Indication: Rett Syndrome

Taysha Gene Therapies, Inc 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.

Taysha Gene Therapies will present new preclinical in vitro data comparing TSHA-102 (scAAV9-miniMeCP2) to an analogous single-stranded AAV9 (ssAAV9) carrying full-length MECP2 in neuronal cell models. The self-complementary AAV9 (scAAV9) produced about 30-fold higher MeCP2 protein expression than ssAAV9, supporting effective delivery of TSHA-102 to the central nervous system by lumbar intrathecal administration. MiniMeCP2 showed similar molecular and biochemical function to full-length MeCP2, with both proteins exhibiting comparable, stable expression in neuronal cells.

These findings validate the choice of scAAV9 and miniMeCP2 for the TSHA-102 construct and offer translational support for the Part A REVEAL Phase 1/2 clinical data in patients with Rett syndrome.

Poster details: "Superior expression of self-complementary AAV and comparable functionality of mini and full-length MECP2 support the design of TSHA-102 gene therapy for Rett syndrome," presented by Ryan Chaparian. Poster session: Thursday, May 14, 5:00–6:30 PM ET; Poster No. 3481; Poster Reception session.

Provided Update - January 6,2026

• Drug: TSHA-102
• Announced Date: January 6, 2026
• Indication: Rett Syndrome

Taysha Gene Therapies, Inc. announced progress across the TSHA-102 pivotal program, an intrathecally (IT) delivered AAV9 gene therapy with disease modifying potential, in clinical evaluation for the treatment of Rett syndrome.

Taysha Gene Therapies reported progress in its TSHA-102 pivotal program, an intrathecal AAV9 gene therapy being evaluated for Rett syndrome. The REVEAL pivotal trial dosed its first patient in Q4 2025 and is enrolling up to 15 females aged 6 to under 22. REVEAL tests a single high-dose IT administration (1x10^15 total vector genomes) and uses each patient as their own control; the primary endpoint is the percentage who gain or regain at least one of 28 developmental milestones. A six-month interim analysis could support a Biologics License Application (BLA).

The company reached written alignment with the FDA to include a minimum of three months of safety data from the ASPIRE trial (three girls aged 2 to under 4, with dose scaled for smaller brain volume) in the planned BLA to help enable a label for patients aged two years and older. Dosing in REVEAL and ASPIRE is expected to complete in Q2 2026, with a longer-term Part A update due in H1 2026.

clinical program - October 16,2025

• Drug: TSHA-102
• Announced Date: October 16, 2025
• Indication: Rett Syndrome

Taysha Gene Therapies, Inc. announced that the Company has regained full rights to its lead TSHA-102 program in clinical evaluation for Rett syndrome.

Taysha Gene Therapies announced it has regained full global rights to its TSHA-102 gene therapy for Rett syndrome after its 2022 option agreement with Astellas expired. This change returns complete control of the program to Taysha, freeing it from licensing restrictions and giving it full strategic flexibility.

In mid-2025, Taysha delivered Phase 1/2 REVEAL data to Astellas, triggering a 90-day review period. When Astellas declined to exercise its option, all rights to TSHA-102 reverted to Taysha without further conditions.

TSHA-102 showed a well-tolerated safety profile and strong early efficacy, and Taysha is set to dose the first patient in its pivotal REVEAL trial this quarter. The single-arm study will assess the gain or regain of key developmental milestones.

With unencumbered rights, Taysha can now advance TSHA-102 through late-stage development and focus on delivering long-term value for patients and shareholders.

Results - October 9,2025

Phase 1/2

• Drug: TSHA-102
• Announced Date: October 9, 2025
• Indication: Rett Syndrome

Taysha Gene Therapies, Inc. announced results from a new supplemental data analysis from Part A of the REVEAL Phase 1/2 adult/adolescent and pediatric trials evaluating TSHA-102 in females with Rett syndrome at the 54th Child Neurology Society (CNS) Annual Meeting.

Taysha Gene Therapies presented a new supplemental data analysis from Part A of the REVEAL Phase 1/2 trials of TSHA-102 in females with Rett syndrome at the 54th Child Neurology Society Annual Meeting. The original results showed a 100% response rate in 10 patients, each gaining or regaining at least one developmental milestone.

The supplemental analysis used reliable rating tools beyond the 28 natural-history milestones. It found that all 10 patients demonstrated multiple additional skills and improvements in everyday abilities, confirming broader functional gains.

In total, the patients achieved 22 developmental milestones plus 165 extra skills or improvements. These gains covered key areas such as communication, fine motor and gross motor skills, plus better autonomic function.

These findings reinforce the consistent, multi-domain impact of TSHA-102 on activities of daily living, suggesting meaningful benefits for patients and caregivers in managing core symptoms of Rett syndrome.

Designation Grant - October 2,2025

Breakthrough Therapy

• Drug: TSHA-102
• Announced Date: October 2, 2025
• Indication: Rett Syndrome

Taysha Gene Therapies, Inc. announced the U.S. Food and Drug Administration (FDA) has granted Breakthrough Therapy designation to TSHA-102, an intrathecally delivered AAV9 gene therapy with disease modifying potential, for the treatment of Rett syndrome.

Taysha Gene Therapies announced FDA granted Breakthrough Therapy designation to TSHA-102, an intrathecal AAV9 gene therapy for Rett syndrome that delivers functional MECP2 to the CNS.

Based on data from 12 patients in Part A of the REVEAL Phase 1/2 trials, TSHA-102 showed a well-tolerated safety profile and a 100% response rate for gaining or regaining at least one developmental milestone at six months.

Taysha also finalized FDA alignment on its pivotal trial protocol and statistical analysis plan. Key elements, like a six-month interim analysis, remain unchanged and may support an early BLA submission based on milestone criteria and early positive responses.

The single-arm, open-label REVEAL pivotal trial will enroll 15 females aged 6 to under 22, each serving as their own control. Enrollment is on track to start in the fourth quarter of 2025 to address the unmet medical need in Rett syndrome.

Oral presentation - June 3,2025

• Drug: TSHA-102
• Announced Date: June 3, 2025
• Indication: Rett Syndrome

Taysha Gene Therapies, Inc. announced details for three oral presentations reviewing recent updates supporting its TSHA-102 program in clinical evaluation for Rett syndrome, and a Taysha-hosted symposium on the Company's analysis of the natural history study data at the 2025 International Rett Syndrome Foundation (IRSF) Rett Syndrome Scientific Meeting, taking place in Boston from June 9-11, 2025.

Taysha Gene Therapies, Inc. announced that it will deliver three oral presentations at the 2025 International Rett Syndrome Foundation (IRSF) Rett Syndrome Scientific Meeting in Boston, scheduled for June 9–11, 2025. These presentations will review recent updates supporting the TSHA-102 gene therapy program currently under clinical evaluation for Rett syndrome. Expert speakers will present data on safety and efficacy, insights from caregivers regarding developmental milestones, and preclinical findings on vector biodistribution following lumbar intrathecal delivery. Additionally, the company will host a symposium titled "Gain and Regain of Developmental Milestones: How Natural History Insights are Redefining the Therapeutic Development for Rett Syndrome." This event underscores Taysha’s commitment to advancing research, improving patient care, and potentially enhancing treatment pathways for a condition with significant unmet medical needs.

Pivotal trial - May 28,2025

• Drug: TSHA-102
• Announced Date: May 28, 2025
• Indication: Rett Syndrome

Taysha Gene Therapies, Inc. announced details of its planned pivotal Part B trial design for TSHA-102 following written alignment from the U.S. Food and Drug Administration (FDA).

Taysha Gene Therapies, Inc. has announced its planned pivotal Part B trial for TSHA-102 after receiving written alignment from the U.S. Food and Drug Administration. The trial will be a single-arm, open-label study designed for females with Rett syndrome who are in the developmental plateau stage (age ≥6 years). In this study, each patient will act as her own control, and the primary goal is to measure the gain or regain of developmental milestones that are critical for daily functioning. The Company’s analysis of natural history data showed that patients six years and older rarely achieve new developmental gains without treatment, making this trial endpoint both objective and significant. Taysha plans to submit the trial protocol and statistical analysis plan as an amendment to its IND application later this quarter, with trial initiation activities expected to begin in the third quarter of 2025.

Positive Data - May 28,2025

Phase 1/2

• Drug: TSHA-102
• Announced Date: May 28, 2025
• Indication: Rett Syndrome

Taysha Gene Therapies, Inc. announced positive clinical data from Part A of the REVEAL Phase 1/2 adolescent/adult and pediatric trials evaluating TSHA-102 in Rett syndrome.

Taysha Gene Therapies, Inc. announced positive clinical data from Part A of the REVEAL Phase 1/2 trials evaluating TSHA-102 for Rett syndrome. In this study, 100% of the 10 patients aged 6 to 21 years gained or regained at least one key developmental milestone, a notable achievement given that natural history data show such milestones are unlikely to be achieved in patients over six years old. The results showed that the high dose of TSHA-102 provided faster and more consistent benefits compared to the low dose, with improvements confirmed across several clinical outcome measures. Additionally, the treatment was generally well tolerated, with no treatment-related serious adverse events or dose-limiting toxicities observed. These encouraging findings support further development of TSHA-102 and its evaluation in a pivotal trial focusing on adolescents and adults who have reached a developmental plateau.

Clinical Data - September 26,2024

• Drug: TSHA-102
• Announced Date: September 26, 2024
• Indication: Rett Syndrome

Taysha Gene Therapies, Inc. announced that it will present previously disclosed clinical data on its TSHA-102 program in evaluation for Rett syndrome during an oral presentation at the upcoming 9th World Rett Syndrome Congress, taking place in Queensland, Australia from October 2-5, 2024.

Taysha Gene Therapies, Inc. announced that it will deliver an oral presentation on its TSHA-102 gene therapy program for Rett syndrome at the 9th World Rett Syndrome Congress in Queensland, Australia, scheduled for October 2–5, 2024. The presentation will include previously disclosed clinical data from the REVEAL Phase 1/2 trials—reporting outcomes up to 52 weeks from the adolescent/adult study and initial findings up to 22 weeks from the pediatric study.

Led by Dr. Sukumar Nagendran, the session will highlight data from different dosing cohorts and provide insights into TSHA-102’s potential as a once‑in‑a‑lifetime treatment. Designed to introduce a functional MECP2 gene directly into the central nervous system, TSHA-102 aims to address the underlying genetic cause of Rett syndrome and offer new hope for patients with this challenging neurodevelopmental disorder.

Dose Update - June 18,2024

• Drug: TSHA-102
• Announced Date: June 18, 2024
• Target Action Date: Q3 2024
• Estimated Target Date Range: July 1, 2024 - September 30, 2024
• Indication: Rett Syndrome

Taysha Gene Therapies, Inc. announced that IDMC approved Company's request for early advancement to cohort two (high dose) in the REVEAL pediatric trial; dosing expected in Q3 2024 following IDMC review of initial safety data from the first high dose patient in the adolescent and adult trial

Taysha Gene Therapies, Inc. announced a key milestone in its REVEAL pediatric trial for Rett syndrome. The company’s Independent Data Monitoring Committee (IDMC) approved the early advancement to cohort two, which involves administering a higher dose. This decision followed an initial safety review from the first high dose patient in the adolescent and adult trial, where the safety data was encouraging. As a result, dosing for the high dose pediatric cohort is expected to begin in the third quarter of 2024. This early advancement reflects Taysha’s commitment to rapidly advancing its gene therapy program and supports ongoing efforts to evaluate transformative treatment options for patients with Rett syndrome. Upcoming safety and efficacy data from this cohort will provide further insights into the potential benefits of the therapy.

Clinical Data - June 18,2024

Phase 1/2

• Drug: TSHA-102
• Announced Date: June 18, 2024
• Indication: Rett Syndrome

Taysha Gene Therapies, Inc. announced positive longer-term clinical data from the ongoing REVEAL Phase 1/2 adolescent and adult trial and initial clinical data from the REVEAL Phase 1/2 pediatric trial evaluating TSHA-102 in Rett syndrome.

Taysha Gene Therapies, Inc. has announced promising longer-term clinical data from its ongoing REVEAL Phase 1/2 trial in adolescent and adult patients, along with early clinical data from a pediatric trial evaluating TSHA-102 for Rett syndrome. In the adult trial, patients showed sustained improvements across several clinical areas, such as enhanced motor skills, better communication, normalized sleep, and a reduction in seizures even after tapering steroid treatments. Notably, one adult patient was able to sit unassisted for the first time in over a decade and experienced improved limb movement. Meanwhile, initial pediatric data revealed improvements in hand function, balance, communication, and new developmental gains, including using eye-gaze communication devices and increased mobility. These positive results support the potential of TSHA-102 as a transformative, one-time intrathecal gene therapy for treating the genetic root cause of Rett syndrome.