FDA Acts to Support Development of Potential Gene Therapy, TSHA-102

The U.S. Food and Drug Administration (FDA) has granted orphan drug and rare pediatric disease designations to TSHA-102, a potential gene therapy for Rett syndrome.

Taysha Gene Therapies, the treatment’s developer, plans to submit an investigational new drug application to the FDA in 2021 to begin testing TSHA-102 in a clinical trial in patients.

Orphan drug designation is intended to encourage the development of therapies for rare diseases (those affecting fewer than 200,000 patients in the U.S.), through benefits such as exemption from FDA fees, financial incentives for clinical development and commercialization, and seven years of market exclusivity if granted approval.

In turn, a rare pediatric disease designation is granted to treatments for serious or life-threatening rare diseases primarily affecting children. If TSHA-102 is ultimately approved, Taysha qualifies for a voucher from the FDA that can be redeemed to obtain priority review of a subsequent experimental medication, or it may sell the voucher to another company.

“Obtaining these designations is a validation of decades-long work to identify and optimize a potential gene therapy treatment for this devastating disease,” R.A. Session II, PhD, president, CEO and founder of Taysha, said in a press release.

TSHA-102 uses a modified, harmless adeno-associated virus (AAV) to deliver a working version of the MECP2 gene. Mutations in this gene are the chief cause of Rett syndrome.

In parallel, the gene therapy is designed to also deliver a regulatory element — called microRNA (miRNA)-Responsive Auto-Regulatory Element or miRARE — to control production of the resulting MeCP2 protein in neurons, the target cells of TSHA-102, and limit potential side effects of this type of therapy.

Notably, micro RNAs are a special class of short RNA molecules capable of regulating gene activity.

Taysha intends to administer its gene therapy via intrathecal injection, directly into the spinal canal, to “facilitate optimal biodistribution” and allow for lower dosing, it states on a webpage.

TSHA-102 is being developed in partnership with UT Southwestern Gene Therapy Program and its Department of Pediatrics, under the direction of Steven Gray, PhD, along with Berge Minassian, MD, chief of the Division of Child Neurology.

“Patients with Rett syndrome are currently managed with symptomatic treatments as there are no therapies approved to treat the underlying cause of disease,” said Minassian, who serves as chief medical adviser for Taysha.

“Gene therapy offers a potentially curative option,” he added. Minassian is credited with describing the version of the MECP2 gene responsible for nerve cell function and communication in the brain.

Added Gray, chief scientific adviser for Taysha: “TSHA-102 represents an important step forward in the field of gene therapy, where we are leveraging a novel regulatory platform called miRARE to prevent the overexpression [increased levels] of MECP2.”