A late stage study has revealed that Spark Therapeutics Inc's experimental gene therapy has aided in improving vision in patients suffering with a type of inherited eye disorder, Reuters reports.

The study brings the treatment closer to becoming the first gene therapy to win U.S. approval. Spark Therapeutics Inc's shares jumped as much as 50.2 percent on Monday.

SPK-RPE65 is a gene therapy that aims to insert corrective genes into malfunctioning cells.

For the study, the researchers tested the drug in 31 patients with IRDs, a broad group of hereditary disorders affecting the retina.

Spark now expects to file for marketing approval in the United States in 2016, which could help it rake in worldwide sales of about $600 million.

The drug, SPK-RPE65, could be worth about $65 per Spark share, Cowen and Co analysts said.

Roth Capital Partners' analyst Elemer Piros said he expects SPK-RPE65 to cost about $100,000 per patient per year, as long as the therapy provides lasting benefit.

Even though gene therapy has been acclaimed as a one-time cure for certain diseases that either have no approved treatment or are expensive to treat, it has invited criticism due to a series of failed results and safety concerns in its more than 20 years of research.

Spark is also carrying out experimental treatments for other conditions including blood disorders and neurodegenerative diseases.