European Commission grants orphan drug designation for rare disease gene therapy

French biotech company Vivet Therapeutics has today announced that the European Commission has granted Orphan Drug Designation for its gene therapy VTX-806, which is under development for the treatment of CTX, a rare genetic disorder.

CTX results from mutations in the CYP27A1 gene, which cause a deficiency of sterol 27-hydroxylase, a mitochondrial enzyme. Without this enzyme, cholesterol cannot be converted into bile acid. This causes a buildup of cholesterol and the compound cholestanol in the central nervous system, tendons, arteries, and eyes.

CTX can occur at any age. Affected children suffer from chronic diarrhea, cataracts, and brittle bones with frequent bone fractures. In adults, CTX causes leukodystrophy, a disease that damages the myelin protein surrounding nerve fibers. As a result, patients suffer from progressive neurological problems, including dementia, seizures, depression, hallucinations, and speech and coordination difficulties.

While there are only several hundred identified cases of CTX patients worldwide, the actual number of affected people is thought to be much higher​. An estimated 1000 to 2000 people are affected by CTX in the EU and the global incidence is thought to be three to five people per 100,000​.

Currently, people with CTX can be treated with chenodeoxycholic acid, which can stabilize or slow down disease progression but can severely affect the liver. There is no cure for CTX at present. Vivet Therapeutics hopes to change that with its VTX-806 gene therapy.

VTX-806 is an adeno-associated viral (AAV) vector that carries the gene CYP27A1, which is mutated in patients with CTX. In preclinical mouse studies, VTX-806 revealed a “normalization of upregulated compensatory enzymes and of primary and secondary bile acids when compared to standard of care treatments,” the company stated in a press release.

Vivet Therapeutics has received €4.9 million in funding from the French government to advance the development of VTX-806. The company aims to apply for Orphan Drug Designation with the FDA this year and plans to begin clinical development in late 2025.

"Early diagnosis and treatment of CTX is crucial to halting disease progression,” said Jean-Philippe Combal, Co-Founder & CEO of Vivet Therapeutics. “At present, existing standard of care treatments can only slow or stabilize leukodystrophy, with no cure available. Preclinical data supports VTX-806's potential as an alternative treatment option to stop or reverse disease progression over the long term, or possibly even cure CTX patients.”