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FDA Approves Gene Therapy to Treat Rare Inherited Vision Loss
The FDA has approved the gene therapy Luxturna (voretigene neparvovec-rzyl, Spark Therapeutics, Inc.) to treat children and adults with an inherited form of vision loss that may result in blindness. Luxturna is the first directly administered gene therapy approved in the U.S. that targets a disease caused by mutations in a specific gene.
Luxturna is approved for the treatment of patients with confirmed biallelic RPE65 mutation-associated retinal dystrophy that leads to vision loss and may cause complete blindness in certain patients.
Hereditary retinal dystrophies are a broad group of genetic retinal disorders associated with progressive visual dysfunction and are caused by mutations in any one of more than 220 different genes. Biallelic RPE65 mutation-associated retinal dystrophy affects approximately 1,000 to 2,000 patients in the U.S.
Biallelic mutation carriers have a mutation (not necessarily the same mutation) in both copies of a particular gene (a paternal and a maternal mutation). The RPE65 gene provides instructions for making an enzyme that is essential for normal vision. Mutations in the RPE65 gene lead to reduced or absent levels of RPE65 activity, blocking the visual cycle and resulting in impaired vision. Individuals with biallelic RPE65 mutation-associated retinal dystrophy experience progressive deterioration of vision over time. This loss of vision, often during childhood or adolescence, ultimately progresses to complete blindness.
Luxturna works by delivering a normal copy of the RPE65 gene directly to retinal cells. These retinal cells then produce the normal protein that converts light to an electrical signal in the retina to restore patient’s vision loss. Luxturna uses a naturally occurring adeno-associated virus, which has been modified using recombinant DNA techniques, as a vehicle to deliver the normal human RPE65 gene to the retinal cells to restore vision.
Luxturna should be given only to patients who have viable retinal cells as determined by treating physicians. Treatment with Luxturna must be done separately in each eye on separate days, with at least six days between surgical procedures. It is administered via subretinal injection by a surgeon experienced in performing intraocular surgery. Patients should be treated with a short course of oral prednisone to limit the potential immune reaction to Luxturna.
The safety and efficacy of Luxturna were established in a clinical development program with a total of 41 patients with confirmed biallelic RPE65 mutations (age range, 4 to 44 years). The primary evidence of efficacy of Luxturna was based on a phase 3 study with 31 participants by measuring the change from baseline to one year in a patient’s ability to navigate an obstacle course at various light levels. The group of patients that received Luxturna demonstrated significant improvements in their ability to complete the obstacle course at low light levels compared with the control group. To further evaluate the long-term safety, the manufacturer plans to conduct a post-marketing observational study involving patients treated with Luxturna.
The most common adverse reactions from treatment with Luxturna included eye redness (conjunctival hyperemia), cataract, increased intraocular pressure, and retinal tear.
The FDA granted this application priority review and breakthrough therapy designations. In addition, Luxturna received orphan drug designation. Spark Therapeutics is also receiving a rare pediatric disease priority review voucher under a program intended to encourage development of new drugs and biologics for the prevention and treatment of rare pediatric diseases.
Source: FDA; December 19, 2017.