Gene Therapy for Blind People Fades Away With Time

A gene therapy that was used to restore sight for patients who suffered from a rare form of childhood blindness seems to wane with time, a worrying sign that the innovative technology may fail to cure some ailments with only one course of treatment.

Shares of Spark Therapeutics Inc., which a producer of similar treatment, dropped the most since in January, when the stock began trading. The waning effect was reported in two studies in the New England Journal of Medicine. The studies didn’t use the same treatment or active therapy as the trials which are conducted by the Philadelphia-based Spark.

The results are a warning for one of biotechnology’s most important fields, where firms like Spark are working on treatments to fix genetic defects that lead to the disease. The scientists and companies gene therapies are collaborating to ensure the best treatments are used.

In studies run in the U.S. and U.K., an improved copy of the gene that produces a protein which is crucial for vision was injected into the patients’ eyes. An investigation on three University of Pennsylvania patients discovered their eyesight was improved for as much as three years. After that, the benefit started to trail off and the patients lost critical photoreceptor cells in the retina at the same pace as in their untreated eyes.

A second research from the University College London’s Institute of Ophthalmology and Moorfields Eye Hospital focused on a dozen patients who got received different doses of the gene therapy. Half presented a modest benefit, with temporary improvement in retinal sensitivity that was at its peak a year after treatment. Three patients suffered from inflammation in the eyes, while two lost visual acuity.

While researchers are disappointed they don’t have a one-time treatment, the results are an “opportunity to improve the therapy so that the restored vision can be sustained for longer durations in patients,” said Samuel Jacobson, the lead researcher of the trial and a professor at Penn’s Scheie Eye Institute in Philadelphia.

The university scientists did not use the same therapy as Spark to cure the condition, which is called Leber congenital amaurosis.

Spark went public in January and its current value is of $1.4 billion. Its product has reached the third and final stage of clinical trials that precedes regulatory approval.

Spark has been examining patients’ status in trials for two to four years and found that their vision gains have lasted, said Chief Executive Officer Jeffrey Marrazzo.

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