TSHA

EX-99.1

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EX-99.1

EX-99.1

Exhibit 99.1

Taysha Gene Therapies Reports Third Quarter 2026 Financial Results and Provides Corporate Update

REVEAL pivotal and ASPIRE trials evaluating TSHA-102 for Rett syndrome ongoing; expect to report

topline data from 6-month interim analysis and FDA feedback on BLA submission pathway in 1H 2027

TSHA-102 continues to be generally well tolerated with no severe treatment-related SAEs or DLTs

across REVEAL Phase 1/2, pivotal and ASPIRE trials (N=33) as of the November 2026 data cutoff

Completed BLA-enabling PPQ manufacturing campaign for TSHA-102, which met predefined product specifications as well as comparability criteria for commercial product and clinical material, supporting potential inclusion of REVEAL Part A Phase 1/2 data in the planned BLA

Encore data supporting TSHA-102 clinical program presented at the 55th Child Neurology Society Annual Meeting

Conference call and webcast today at 8:30 AM ET

Dallas – November 12, 2026 – Taysha Gene Therapies, Inc. (Nasdaq: TSHA) (Taysha or the Company), a clinical-stage

biotechnology company focused on advancing adeno-associated virus (AAV)-based gene therapies for severe monogenic diseases of the central nervous system (CNS), today reported financial results for the third quarter ended September 30, 2026, and provided a corporate update.

“During the third quarter, we continued to make strong progress across our clinical, manufacturing and commercial readiness activities as we advance toward a potential BLA submission for TSHA-102,” said Sean P. Nolan, Chairman and Chief Executive Officer of Taysha. “With all patients dosed and having cleared the acute post-dosing safety monitoring period in our REVEAL pivotal and ASPIRE trials with no severe treatment-related serious adverse events or dose-limiting toxicities observed across all studies, our focus now turns to delivering a robust dataset to support our planned BLA submission and further establish the potential of TSHA-102 to address the significant unmet need in Rett syndrome. In parallel, we achieved an important manufacturing milestone with the successful completion of our BLA-enabling PPQ manufacturing campaign, which met the predefined acceptance and comparability criteria previously reviewed with FDA. Importantly, the results further demonstrated our ability to consistently manufacture high-quality product at commercial scale, including an encouraging single-digit empty capsid percentage, a key indicator of product quality that contributes to patient safety. Looking ahead, we believe the first half of 2027 could be a transformative period for Taysha with our plan to report data from the six-month interim analysis of our REVEAL pivotal trial along with expected FDA feedback on our BLA submission pathway, and the anticipated nomination of a second gene therapy development program with a high unmet medical need and robust commercial opportunity as we begin building a broader CNS genetic medicine franchise.”

Recent Corporate and TSHA-102 Program Highlights

•

REVEAL Pivotal and ASPIRE Trials Ongoing with TSHA-102 Continued to be

Generally Well-Tolerated. High dose (1x1015 total vector genomes (vg)) and low dose (5.7x1014 total vg) TSHA-102 continue to be generally well tolerated with no severe treatment-related serious adverse events (SAEs) or dose limiting toxicities (DLTs) in all patients treated in the REVEAL Phase 1/2, REVEAL pivotal and ASPIRE trials (N=33) as of the November 2026 data cutoff. All patients in the REVEAL Phase 1/2 (n=12), pivotal (n=17) and ASPIRE (n=4) trials have cleared the acute post-dosing safety monitoring period typically associated with AAV gene therapies with no dose-limiting toxicities observed across all trials.

•

Completed BLA-Enabling Process Performance Qualification (PPQ)

Campaign for TSHA-102. Following alignment on the company’s proposed PPQ strategy with the U.S. Food and Drug Administration (FDA), Taysha completed its Biologics License Application (BLA)-enabling PPQ manufacturing campaign for TSHA-102, including the successful production of commercial-scale drug product batches required to validate the final commercial manufacturing process in support of a potential BLA submission and future commercialization of TSHA-102.

•

All process parameters and analytical results met predefined product specifications as well as comparability criteria for commercial product and clinical material. Together with the comparability of the clinical material used across the REVEAL Part A and Part B pivotal trials, these results support the potential inclusion of REVEAL Part A data in the planned BLA submission.

•

The final TSHA-102 commercial manufacturing process consistently achieved

a single-digit empty capsid percentage, an important indicator of product quality that contributes to patient safety. The PPQ results also demonstrate the process consistency and scalability required to support potential commercial demand. T

EX-99.1

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EX-99.1

EX-99.1

Exhibit 99.1

Taysha Gene Therapies Reports Second Quarter 2026 Financial Results and Provides Corporate Update

Completed dosing in the REVEAL pivotal (N=17) and ASPIRE (N=4) trials evaluating TSHA-102 for Rett syndrome; expect to report topline data from 6-month interim analysis and FDA feedback on the BLA submission pathway in 1H 2027

TSHA-102 continues to be generally well tolerated with no severe treatment-related SAEs or DLTs across REVEAL Phase 1/2, pivotal and ASPIRE trials (N=33) as of the August 2026 data cutoff

Longer-term REVEAL Part A data demonstrated broad, multi-domain functional gains that deepened through ≥12 months post-TSHA-102, with consistent responses across ages and disease severity

Advanced TSHA-102 commercial readiness activities, including market access planning initiatives and expansion of strategic partnership with Catalent to support future commercial manufacturing

Completed $230 million follow-on offering, extending cash runway into 2H 2028 and through potential BLA approval of TSHA-102

Conference call and webcast today at 4:30 PM ET

Dallas – August 11, 2026 – Taysha Gene Therapies, Inc. (Nasdaq: TSHA) (Taysha or the Company), a clinical-stage

biotechnology company focused on advancing adeno-associated virus (AAV)-based gene therapies for severe monogenic diseases of the central nervous system (CNS), today reported financial results for the second quarter ended June 30, 2026, and provided a corporate update.

“During the second quarter, we continued to execute against our clinical development strategy for TSHA-102 while advancing key commercial and manufacturing readiness initiatives in support of a potential BLA submission,” said Sean P. Nolan, Chairman and Chief Executive Officer of Taysha. “The completion of dosing in our REVEAL pivotal and ASPIRE trials, as well as positive longer-term follow-up data from our REVEAL Phase 1/2 trials continues to strengthen our conviction in TSHA-102 as a potentially transformative therapy for this devastating disease with high unmet need. In addition, the favorable safety profile observed to date across a broad and diverse patient population supports TSHA-102’s potential to safely deliver durable, meaningful functional benefits.”

Mr. Nolan continued, “We are working diligently to advance our commercial readiness activities to support the potential launch of TSHA-102, if approved. Our ongoing market and payer research continues to inform our market access strategy and reinforces TSHA-102’s significant value proposition and reimbursement potential. We have also expanded our partnership with Catalent, establishing a robust commercial supply framework to support the potential launch of TSHA-102 and strong demand we expect following potential FDA approval. Looking ahead, with a strengthened balance sheet, we remain focused on executing our BLA-enabling activities and anticipate reporting topline data from the REVEAL pivotal trial six-month interim analysis and FDA feedback on the BLA submission pathway in the first half of 2027.”

Recent Corporate and TSHA-102 Program Highlights

•

Completed Dosing in the REVEAL Pivotal Trial. Taysha completed dosing in the overenrolled REVEAL pivotal trial, with a total of 17 patients in the developmental plateau population of Rett syndrome dosed with TSHA-102. The REVEAL pivotal trial is a single-arm, open-label trial evaluating a single intrathecal (IT) administration of high dose TSHA-102 (1x1015 total vector genomes (vg)) in females with Rett syndrome between the ages of 6 to <22 years. The primary endpoint will assess response rate, defined as the percentage of patients who gain or regain ≥one of the 28 natural history-defined developmental milestones, with each patient serving as their own control.

•

The study includes a 6-month interim analysis that may serve as the basis for Biologics License Application (BLA) submission. The interim analysis is expected to occur after all 17 patients complete six months of post-treatment follow-up. Subsequently, Taysha plans to discuss data from the 6-month interim analysis and next steps in the BLA submission pathway with the U.S. Food and Drug Administration (FDA) and is on track to report topline data and regulatory feedback in 1H 2027.

•

Completed Dosing in the ASPIRE Trial. Taysha completed dosing in the overenrolled ASPIRE trial, with a total of four patients with Rett syndrome, aged 2 to <4 years, dosed with TSHA-102. The safety-focused trial is evaluating the safety and preliminary efficacy of a single IT administration of high dose TSHA-102 (1x1015 total vg), scaled to account for the lower brain volume in 2 to <4-year-olds. ASPIRE is designed to support a planned BLA submission to enable broad labeling of TSHA-102 for patients aged ≥2 years with Rett syndrome. A minimum of three months of ASPIRE safety data will be included in the planned BLA submission, while efficacy in the 2 to <6-year-old populati

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