Rett Syndrome Treatment TSHA-102 Received Rare Pediatric Disease and Orphan Drug Designations

Recently, gene therapy company Taysha Gene Therapies (“Taysha”) announced that its gene therapy candidate, TSHA-102, received both Orphan Drug and Rare Pediatric Disease designations from the FDA. TSHA-102, delivered via AAV9 vectors, is designed to treat patients with Rett syndrome. Currently, there are no treatments designed to treat the underlying causes of Rett syndrome; instead, most therapies are symptomatic and supportive.


Gene therapy usually works by delivering a functional copy of a gene to patients. In this case, TSHA-102 delivers a working MECP2 gene. However, TSHA-102 also uses the proprietary miRNA-Responsive Auto-Regulatory Element (miRARE) technology to prevent the over expression of MECP2. In short, this regulatory system is built into the gene therapy. This allows the gene therapy to regulate gene expression but prevent any over expression that might lead to damage or further disease progression.

Rare Pediatric Disease designation is granted to therapies designed to treat pediatric patients (birth through age 18) with rare diseases. Orphan Drug designation is granted to therapies focused around treating patients with rare diseases. In both cases, rare diseases are defined as those impacting 200,000 people or under in the United States. Both programs offer benefits, such as increased communication with the FDA, priority review vouchers, and market exclusivity.

For the next steps, Taysha looks to submit an Investigational New Drug (IND) application for its gene therapy by next year.

Rett Syndrome

Caused by X chromosome mutations, as well as MECP2 gene mutations, Rett syndrome is a rare neurological disorder that causes severe developmental and intellectual delays. Most patients with Rett syndrome are female. However, in rare cases, male infants can develop Rett syndrome genetic mutations. Male patients rarely live past birth or infancy. An estimated 25,000 patients between Europe and the United States have Rett syndrome.

While symptom onset varies, symptoms usually occur between 1 year to 18 months. These include:

  • Seizures
  • No language skills
  • Social anxiety
  • Slow brain development
  • Problems with muscle coordination
  • Breathing issues
  • Sleep disturbances
  • Irritability

Learn more about Rett syndrome.

Jessica Lynn

Jessica Lynn

Jessica Lynn has an educational background in writing and marketing. She firmly believes in the power of writing in amplifying voices, and looks forward to doing so for the rare disease community.

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