Spark Therapeutics is on course to earn the first U.S. approval for a so-called gene therapy. The Philadelphia-based biotech company said Monday that it saw positive results from a late-stage clinical trial to use gene editing to treat a rare form of inherited vision loss that can lead to blindness. 

Gene therapy represents a radical new pathway for the potential treatment of hundreds of diseases by replacing malfunctioning genes with normal ones. Researchers and biotech companies have sought to commercialize gene therapy for decades. Spark's announcement marks the first successful trial for the use of gene therapy to treat genetic diseases. 

Spark plans to file an application for approval with the U.S. Food and Drug Administration in 2016. If approved, the technique will be the first therapy to use gene editing for any disease in the U.S. The company is backed by more than $268 million from investors including the Children's Hospital of Pennsylvania, whose researchers formed the original plans for the company, and money raised in an initial public offering in January. 

After the announcement, Spark Therapeutics' stock jumped 23 percent, or $10.07, to $54 in Monday trading.

Gene editing is a process through which mutated genes are replaced or supplemented with healthy ones that are inserted directly into a patient’s genome. All previous attempts to treat genetic disorders through similar methods have failed to demonstrate improvement or win regulatory approval. Last spring, researchers found that the initial benefits of another form of gene editing that had shown early promise in reversing blindness faltered after about three years.

Spark’s new drug, SPK-RPE65, treats a form of visual loss known as retinal dystrophies that is inherited through a mutation of a specific gene called RPE65. Patients with the disease experience a gradual loss of vision, starting with peripheral vision and ability to see at night and often culminating in the loss of color vision or the ability to read. In rare cases, the disorder can lead to total blindness.

"We saw substantial restoration of vision in patients who were progressing toward complete blindness,” Dr. Albert M. Maguire, an ophthalmologist at the University of Pennsylvania who led the company’s trials, said in a statement. “If approved, SPK-RPE65 should have a positive, meaningful impact on the lives of patients with this debilitating condition."

The company said the treatment met the primary goal in patients in a phase three clinical trial, which was the improvement of functional vision compared with a control group. Twenty-one subjects who received the therapy were asked to repeatedly navigate a course in varying levels of low light over a period of one year and their results were compared with those of 10 people in the control group. The treatment also was successful in meeting two of three secondary goals. The company reported no serious side effects from the trial.