Clinical Trial Updates: Gene Therapy

June 6th, 2017 by FFB Canada

Many experts agree that gene replacement therapy is a novel approach to treating inherited degenerative retinal diseases, especially when the disease is caused by a single gene defect (or mutation). Gene replacement therapies are sometimes described as “gene addition” or “gene augmentation” therapies because the treatment strategy involves replacing a damaged gene with a new, functioning copy.  The functioning copy allows the body to produce proteins that help the cell work effectively.

There is a lot of enthusiasm about the future of gene therapy to treat blinding eye diseases. This optimism is fueled by exceptional scientific developments, which laid the foundation for a number of innovative biotechnology companies, such as Spark Therapeutics, Novelion Therapeutics, RetroSense Therapeutics, and AGTC, who are committed to making gene therapies a reality.

In 2012, FFB donors funded Dr. Robert Molday’s ground-breaking research about X-linked retinoschisis (XLRS). Building on Dr. Molday’s findings in the laboratory, AGTC designed a clinical trial to test if a gene-therapy approach could work as a treatment for XLRS. Currently, AGTC is translating critical scientific discoveries into gene therapies for x-linked retinoschisis; achromatopsia; x-linked retinitis pigmentosa; and age-related macular degeneration.

AGTC is currently recruiting individuals with X-linked Retinoschisis (XLRS) and Achromatopsia from the United States and Canada to participate in gene therapy trials at several sites throughout the U.S. For more information on the trial and to learn if you or a loved one might be eligible, you can learn more details about the trial here.

X-linked retinoschisis (XLRS) is caused by mutations in the RS1 gene. XLRS is a rare inherited retinal disease that causes layers of the retina to separate. This separation can cause poor vision. XLRS symptoms usually start by school age and may become worse during teenage years.  XLRS causes a loss in central vision, but sometimes peripheral vision might also be damaged. In males, XLRS is the leading cause of juvenile macular degeneration. The word “retinoschisis” means splitting of the retina. In XLRS, tiny splits appear in the retina between the photoreceptor cells and the next layer of nerve cells which relay their signals to the brain. Cysts form in these splits, which causes a loss of central vision. These splits and cysts also make the retina abnormally thick. Over time, damage to the retina builds up causing progressive loss of vision.  XLRS almost always affects boys, usually starting in childhood.

AGTC is conducting a phase 1/2 clinical trial in patients with XLRS. The trial will test if inserting the working copy of the gene into the eye is safe (this is the purpose of phase 1 trials) and will also measure effects on visual acuity and the degree of splitting of the retina. The trial is open to patients living in both Canada and the US. If you are eligible, AGTC will cover all study-related costs and provide compensation to assist with travel expenses.

Achromatopsia is an inherited condition that is associated with loss of visual acuity, extreme light sensitivity resulting in daytime blindness, and reduced or complete loss of color discrimination. It is caused by mutations in any of several genes. The most common genes are the CNGB3 and CNGA3 genes.  AGTC is working on two programs based on the gene mutations known as CNGB3 and CNGA3, which account for 75 percent of the patient population. There is no specific treatment for achromatopsia, although deep red tinted spectacles or contact lenses can reduce symptoms of light sensitivity.

AGTC is conducting a phase 1/2 clinical trial in patients with Achromatopsia in individuals who have documented CNGB3 and CNGA3 mutations. The trial will test if inserting the working copy of the gene into the eye is safe (this is the purpose of phase 1 trials) and will also measure effects on visual acuity, light discomfort and color vision. The trial is open to patients living in both Canada and the US. If you are eligible, AGTC will cover all study-related costs and provide compensation to assist with travel expenses. To learn if you or a loved one might be eligible, you can find more details about the trials here (CNGB3) or here (CNGA3).

There are many ongoing gene therapy trials happening around the world. At the FFB, we are working to gather trusted, up-to-date, information about these trials to share with all of you! If you want to learn more about gene therapy, we hope that you will tune into our Facebook Live session on Friday, June 9 at 11 am (EST).