Taysha Gene Therapies (NASDAQ:TSHA) said it completed dosing in its REVEAL pivotal trial and ASPIRE trial for TSHA-102, its gene therapy candidate for Rett syndrome, while preparing for a potential biologics license application submission.
Chief Executive Officer Sean Nolan said the company dosed 17 patients in the over-enrolled REVEAL pivotal trial and four patients ages 2 to under 4 in the ASPIRE study. The REVEAL trial enrolled pediatric, adolescent and adult patients, which Nolan said reflects the broader Rett syndrome population.
Part A Data Showed Milestone Gains
Sukumar Nagendran, Taysha’s president and head of research and development, discussed longer-term data from Part A of the REVEAL Phase I/II trial presented at the International Rett Syndrome Foundation scientific meeting. As of a May 2026 data cutoff, all 12 treated patients had at least 12 months of follow-up.
Using the FDA-aligned developmental milestone assessment criteria planned as the pivotal trial’s primary endpoint, Taysha reported that 75% of Part A patients were responders at three months, 83% were responders at six months and all 12 patients were responders by 12 months. The company said the FDA-aligned minimum efficacy threshold for the pivotal trial is a 33% response rate.
Patients achieved 31 total developmental milestones, including 16 among six pediatric patients and 15 among six adolescent and adult patients, according to Nagendran. At 12 months and beyond, the company recorded 310 functional gains across communication, fine motor, gross motor and autonomic domains, averaging 26 gains per patient.
Taysha also presented a Rett syndrome natural-history analysis indicating that developmental progress plateaus after age 6 and that the chance of gaining or regaining a lost developmental milestone declines to less than 6.7%. Nagendran said the data support REVEAL’s minimum enrollment age of 6 and help distinguish observed trial gains from the disease’s expected natural history.
The company additionally cited a methods study supporting the developmental milestone assessment as a psychometrically valid and FDA-supported endpoint for a single-arm interventional study.
Safety Event Reported During Pivotal Trial
Taysha said both high- and low-dose TSHA-102 have been generally well tolerated. Across 33 patients treated in the REVEAL Phase I/II, pivotal and ASPIRE studies as of the August 2026 cutoff, the company reported no severe treatment-related serious adverse events or dose-limiting toxicities.
However, one patient in the REVEAL pivotal trial experienced a treatment-related Grade 2 peripheral sensory neuropathy about six weeks after treatment in early July. The patient was admitted overnight under the treating institution’s policy, causing the event to be technically classified as a serious adverse event, Nolan said. The patient was discharged the next day and showed substantial recovery, according to the company.
Nagendran said peripheral sensory neuropathy is a known risk associated with AAV9-based therapies and can be managed with immunomodulatory agents when clinically needed. He said Taysha reported the event to the FDA and its independent data monitoring committee, neither of which had raised concerns or recommended changes to the company’s approach as of the call.
The company said prophylactic immunomodulation can reduce, but not necessarily prevent, the incidence of peripheral neuropathies after AAV9 gene therapy. Taysha said it has not observed worsening seizures in treated patients. Seizure-related data, including electroencephalogram information collected in the pivotal trial, are exploratory rather than primary or secondary endpoints.
Manufacturing and Commercial Preparations Continue
Taysha expanded its partnership with Catalent to include commercial manufacturing support for TSHA-102 if the therapy is approved. Manufacturing is planned at Catalent’s FDA-licensed gene therapy facility in Harmans, Maryland. Nolan said BLA-enabling process performance qualification activities are underway and remain on track for completion in the fourth quarter of 2026.
During the question-and-answer session, Nolan said the company has discussed comparability between its clinical product lot and commercial manufacturing lots with the FDA. He said the agency has considered the lots analytically comparable to date, and that completing the process performance qualification runs is the remaining major manufacturing step ahead of a subsequent FDA discussion.
The company also completed payer research that Nolan said found support for TSHA-102’s potential value proposition. According to Taysha, payers focused on the potential for durable functional gains, safety and efficacy. Nolan said payers viewed a one-time intrathecal administration as less invasive than some other direct-to-central-nervous-system delivery approaches and noted its potential use in outpatient settings.
Taysha appointed Mike Johannesen as chief legal officer during the quarter. The company also said it plans to provide additional details on its prospective commercial organization and market-access strategy later in 2026 or early 2027.
Quarterly Loss Widens as Development Spending Rises
- Research and development expense rose to $38.6 million in the second quarter from $20.1 million a year earlier, primarily due to BLA-enabling manufacturing work, higher clinical-trial costs and additional R&D headcount.
- General and administrative expense increased to $12.1 million from $8.6 million, driven by compensation, consulting, professional fees and launch-readiness initiatives.
- Net loss was $46.6 million, or $0.13 per share, compared with a net loss of $26.9 million, or $0.09 per share, in the prior-year quarter.
- Cash and cash equivalents totaled $455.4 million as of June 30, including proceeds from a $230 million June follow-on financing.
Chief Financial Officer Kamran Alam said Taysha expects its cash resources to fund planned operating expenses and capital requirements into the second half of 2028.
About Taysha Gene Therapies (NASDAQ:TSHA)
Taysha Gene Therapies, Inc (NASDAQ: TSHA) is a clinical-stage biotechnology company focused on developing gene therapies for rare monogenic diseases of the central nervous system. Using a proprietary adeno-associated viral (AAV) vector platform, the company engineers novel capsids and regulatory elements to optimize delivery and expression of therapeutic genes. Its pipeline features lead programs such as TSHA-102 for GM2 gangliosidoses (Tay–Sachs and Sandhoff diseases), TSHA-101 for GM1 gangliosidosis and TSHA-103 for aromatic l-amino acid decarboxylase (AADC) deficiency, alongside earlier-stage candidates targeting other life-threatening pediatric CNS disorders.
Founded in 2019 and headquartered in Dallas, Texas, Taysha Gene Therapies completed its initial public offering in May 2021.
