Spark Therapeutics has announced the success of their SPK-RPE65 gene therapy in the final stages of clinical trials. This form of gene therapy is designed to treat a rare form of hereditary blindness.

Gene therapy involves replacing the mutated genes in the body and replacing them with healthy ones. According to The New York Times, since 1990, the number of studies involving gene therapy could now be in the hundreds but none have been as successful as the SPK-RPE65.

In an article by the Bloomberg Business, it is stated that the SPK-RPE65 is designed to treat a rare form of genetic eye disease known as the RPE65. Replacing the defective gene will theoretically improve the condition of the eye's photoreceptors, making them more sensitive to light.

According to The New York Times, Spark plans to apply for a license to sell in 2016. If successful, the SPK-RPE65 will be the first of its kind to be approved for use in the US market.

Dr. Katherine High, president of Spark Therapeutics, says that "I've been working in gene therapy for most of my career." In the same article by the New York Times, Dr. High continues on stating, "It's been a long time coming, and I'm delighted."

Bloomberg Business states that two similar tests were conducted in May but produced dismal results. In those two tests, the improvements experienced by the patients were short-lived while the benefits were expected to last only for a few years.

In Spark's press release, Principal investigator and ophthalmology professor at the University of Pennsylvania's Perelman School of Medicine, Dr. Albert Maguire, has been ecstatic with the results stating that, "We saw substantial restoration of vision in patients who were progressing toward complete blindness." He goes on to say that "if approved, SPK-RPE65 should have a positive, meaningful impact on the lives of patients with this debilitating condition."

According to CNBC's interview with Spark's Chief Executive Officer Jeff Marrazzo, approximately 3,500 individuals in the country are afflicted with the RPE65 gene mutation. This flaw starts with gradual vision loss until the individual becomes completely blind.

The SPK-RPE65 aims to reverse the effects by replacing the flawed gene with a working one. Bloomberg Business reports that once the gene therapy is approved for public use, interested patients may pay for the treatment in installments.

In the same report by Bloomberg Business, analysts have speculated that the treatment may cost at least $1 million, making it the most expensive therapy available in the US. In Europe, a different gene therapy product is being priced at an equivalent of $1.23 million.