Taysha highlights early Rett gene therapy data, but safety concerns reduce excitement

Taysha Gene Therapies recently shared promising new data for its Rett syndrome gene therapy, focusing on clinical improvements in two adult and two pediatric patients. Despite the positive results, the company's stock plummeted by over 26%, likely due to concerns regarding "challenging side effects" observed in the pediatric patients.

The biotech firm clarified that the adverse events (AEs) in the children were linked to a separate immunosuppressant treatment, not the gene therapy itself, TSHA-102. These serious AEs have since been resolved. Taysha highlighted that TSHA-102 exhibited a well-tolerated safety profile without any dose-limiting toxicities. An independent data monitoring committee has authorized the company to start testing a higher dose in pediatric patients in the upcoming third quarter.

The early data for the pediatric patients and the long-term data for the adults showed improvements in several clinical areas such as motor skills, communication, socialization, autonomic function, and seizure management.

The REVEAL Phase I/II study administered the gene therapy to four patients aged six, seven, 20, and 21. Follow-up data was gathered for 12 weeks, eight weeks, 52 weeks, and 36 weeks post-treatment, respectively.

Both adult patients exhibited improved breathing patterns and circulation. The 20-year-old patient also showed enhanced hand function and vocalization, achieving the ability to sit unassisted, with stable seizure events. The 21-year-old demonstrated better posture and stability, increased social engagement, and a significant reduction in seizures.

Elsa Rossignol, the principal investigator for the adult cohort, remarked, "It’s encouraging that we continue to see improvements across multiple clinical domains in the longer-term assessments with no diminution of effect."

Similarly, the pediatric patients showed progress in hand function and social interest. The seven-year-old child maintained eye contact more frequently, walked with greater stability, and had more seizure-free days. The six-year-old exhibited improved swallowing, better communication, and reduced breath-holding episodes.

Colleen Buhrfiend, the principal investigator for the pediatric portion of the trial, commented, "The initial improvements observed across multiple areas of disease in both pediatric patients are encouraging early signs of possible benefit."

Taysha's recent findings shed light on the potential of gene therapy for Rett syndrome, offering hope for better management of this challenging condition. The firm is moving forward with its plans to test higher doses in pediatric patients, aiming to further explore the therapy's efficacy and safety.