Philadelphia gene therapy company Spark Therapeutics has applied to the European Medicines Agency for approval to sell its treatment of rare inherited blindness in the European Union.

The experimental therapy, Luxturna, or voretigene neparvovec, is under priority review with the U.S. Food and Drug Administration, with a possible approval date of Jan. 12, 2018.

Spark was spun out of Children's Hospital of Philadelphia, based on research led by Katherine A. High, Spark's cofounder, president, and chief scientific officer. If approved, it would be the first gene therapy for a genetic disease in the United States.

"With Luxturna now in regulatory review on both sides of the Atlantic, we are building out our medical and commercial infrastructure" to bring the drug to patients, said John Furey, Spark's chief operating officer. For the first time, adults and children, who otherwise would progress to complete blindness, "have hope for a potential treatment option that may restore their vision," he said.

About 3,500 people in the United States and Europe live with the disease.

The review period will begin in Europe once the agency validates the application, Spark said.