NEW YORK (TheStreet) -- Shares of Spark Therapeutics (ONCE) - Get Report, a company investigating gene therapy whose most advanced product candidate, SPK-RPE65, is being studied as a treatment of rare blinding conditions, is falling in early trading after the New England Journal of Medicine published a study from the University of Pennsylvania that found gene therapy that previously helped restore sight in patients with LCA, a rare form of childhood blindness, peaked one to three years after treatment and then diminished.

WHAT'S NEW: In the new study of gene therapy for Leber congenital amaurosis, or LCA, the research team at the Perelman School of Medicine at the University of Pennsylvania reported long-term follow-up from three of the earliest treated patients among the initial cohort of 15 patients who received the investigational therapy. "This study shows that the current therapy doesn't appear to be the permanent treatment we were hoping for, but the gain in knowledge about the time course of efficacy is an opportunity to improve the therapy so that the restored vision can be sustained for longer durations," said lead author Samuel Jacobson.

WHAT'S NOTABLE: Spark Therapeutics announced that it will have several presentations during the Annual Meeting of the Association for Research in Vision and Ophthalmology, or ARVO, taking place May 3-7.

PRICE ACTION: In early trading, shares of Spark Therapeutics dropped 18.3% to $47.80.

Reporting by Jason Keil.

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