COVID-19 Vaccine Compatible with Trial Testing of Rett Gene Therapy

People with Rett syndrome can receive the COVID-19 vaccine from Johnson & Johnson and still participate in future clinical trials of the investigational gene therapy TSHA-102, the treatment’s developer has announced.

“We are aware of concerns about the adenovirus vector COVID-19 vaccine from Johnson & Johnson (J&J) and its potential impact on eligibility to receive an investigational gene therapy in the future,” Taysha Gene Therapies wrote in a statement published by Reverse Rett.

“However, available evidence suggests that receiving the J&J COVID-19 vaccine will not disqualify an individual from participation in any potential clinical trial with TSHA-102, Taysha’s investigational AAV9 gene therapy product candidate for Rett syndrome,” the company stated.

Although both TSHA-102 and the J&J vaccine use viral vectors to deliver their respective therapies, each uses a genetically unrelated virus.

TSHA-102 employs an adeno-associated virus serotype 9 (AAV9) vector, while the J&J vaccine uses an adenovirus type 26 (Ad26).

The same holds true, the company stated, for the AstraZeneca-Oxford vaccine, made with an adenovirus ChAdOx1 vector.

The two types of virus — adeno and adeno-associated — share some similar features, such as an ability to infect a broad range of hosts, as well as both dividing and non-dividing cells. Their distinct genetic makeup, however, causes them to provoke different immune responses. Engineered forms are common vectors, or biological vehicles to deliver gene therapies to cells.

Taysha has been developing TSHA-102 and other gene therapies in collaboration with Yale University, the Cleveland Clinic, and others. For the time being, the potential therapy remains in the preclinical testing phase.

TSHA-102 delivers a mini- and nerve cell-specific version of the MECP2 gene. Mutations in this gene, which carries instructions for making a protein needed for normal brain function, underlie most cases of Rett syndrome.

The U.S. Food and Drug Administration (FDA) granted TSHA-102 orphan drug and rare disease designations for the treatment of Rett in October 2020. These designations convey several benefits to facilitate a potential therapy’s development.

Taysha plans to submit an investigational new drug application to the FDA in the second half of this year, so it can begin clinical testing.

The FDA granted the J&J COVID-19 vaccine emergency use authorization in late February, based on trial data that showed the vaccine to be approximately 85% effective at preventing severe forms of the disease, as well as hospitalization and death.

This vaccine is currently being distributed throughout the U.S. It has not yet been approved in the U.K. but a decision is expected soon.

The AstraZeneca-Oxford vaccine has been approved in the U.K. and the European Union but not yet in the U.S. Recently released data, which AstraZeneca said will be the basis of a regulatory submission for emergency use authorization to the FDA, showed 76% efficacy against symptomatic COVID-19 and 100% against severe disease and hospitalizations.

The two other available COVID-19 vaccines, from Moderna and Pfizer-BioNTech, do not use viral vectors.