Biotechnology startup Spark Therapeutics Inc. announced that its experimental gene therapy meant for visually impaired patients helped improve the vision in a clinical trial. The company said the therapy also does not have any serious safety problems.

The Philadelphia-based company announced the results of the clinical trial in a news release, along with some details. The company said that the additional data will be presented at a medical meeting in Paris on October 10.

The company said in a statement that after the success of the trial it is planning to seek the US Food and Drug Administration (FDA) approval to market its treatment next year. The approval from the FDA will make it the first ever gene therapy to reach the US market if regulators approve it for sale. Shares of the company closed 21% higher at $53.02 Monday.

Spark's gene therapy, SPK-RPE65, includes injecting genetic material into a person's cells to treat or prevent a disease. The research stalled after some study participants died or developed cancer after receiving gene therapies in the late 1990s and 2000s.

But the gene therapy started to become famous later when in 2012; the European Commission approved the Western world's first gene therapy, UniQure NV's Glybera, for the treatment of patients with a rare enzyme deficiency.

Spark's therapy, SPK-RPE65, targets mutations in a gene known as RPE65, which can cause visual impairments including loss of night- and peripheral-vision. Spark's therapy contains a copy of a functional RPE65 gene that is encapsulated in a type of virus stripped of its viral DNA The virus acts as a delivery vessel for the gene, and is injected into the eyes.

Researchers for the study tested the therapy in 19 people with confirmed RPE65 gene mutations and compared their outcomes with nine patients who didn't receive the therapy. Patients receiving the therapy showed improvement as compared to the control group.

"We've all been hoping gene therapy will be approved for treating these retinal disorders, and to see the first example of that getting very close is exciting," said Dr. Thompson, who has conducted research on hereditary retinal disorders but wasn't involved in Spark's studies.