Partnership pushes efforts to cure achromatopsia forward
Collaboration of researchers, patients, and funding agencies sets the stage for gene therapy trial to treat achromatopsia in humans.
Many people have never heard of achromatopsia, a relatively rare genetic condition affecting 1 in 30,000 people in the US. Achromatopsia is derived from the Greek word “achromatos”, which means “without color”; patients with achromatopsia have absent color vision, along with a number of other visual impairments. Believed to be untreatable, little effort was made towards understanding the condition or exploring new ways to manage the symptoms. This changed with the advent of gene therapy – a technique that can introduce a healthy copy of a specific gene into a patients’ retina. Despite being rare, achromatopsia was near the top of the list of conditions to apply these new genetic tools to. This was due to the fact that there were naturally-occurring animal models of achromatopsia and that the genetic basis for achromatopsia was well understood. In 2007, cone function was restored in a mouse model of achromatopsia and in 2010 the same was demonstrated in a dog model. These early successes provided significant hope for patients and their families, though the path to a cure for humans is a challenging one.
What Causes Achromatopsia? Normally, the human retina contains some 100 million photoreceptors – light specialized cells that convert incoming light energy into a signal that is sent to the brain. There are two general types of photoreceptor – called rods and cones. Rods are sensitive in low light levels and support night vision, while cones provide our high acuity and color vision. Achromatopsia results when there are mutations in proteins within the cone cells that prevent them from functioning normally – the result is a complete absence of cone function. This absence of cone function results in a variety of visual deficits, including photophobia or pain under bright light, poor visual acuity, nystagmus (rapid uncontrolled eye movements) and absent color vision.
Gene therapy trial to treat achromatopsia in humans
Thanks to the dedication and collaboration of researchers, patients, and funding agencies, we are very close to the start of the first clinical trial using gene therapy to treat achromatopsia in humans. The Advanced Ocular Imaging Program (AOIP) at the Medical College of Wisconsin has led groundbreaking research on imaging the retina in patients with achromatopsia. The AOIP has tools that allow non-invasive visualization of individual cone photoreceptors, which was used to provide a critical piece of information for the effort to treat achromatopsia. While it was known that patients with achromatopsia have no cone function, it was not clear whether they had any cone structure. Without remaining cones in the retina, there would be no cells for the gene therapy to target. Using their advanced retinal imaging tools, the AOIP was able to show that nearly all patients with achromatopsia indeed have remaining cone photoreceptors. “The fact that patients with achromatopsia can have robust remnant cones in their retina supports the therapeutic potential for this condition,“ said Joseph Carroll, PhD, co-director of the AOIP.
Building on these early results, the AOIP was invited to participate in the national multi-center natural history trial funded by the National Institutes of Health and Applied Genetic Technologies Corporation (AGTC) led by Dr. William Hauswirth at the University of Florida. The focus of this trial is to monitor retinal structure and function over time in patients with achromatopsia, using a diverse battery of tests that often require multiple days to perform. This sort of longitudinal data is needed to determine which tests may be most appropriate to use in future treatment trials as well as to define the baseline state of the retina in achromatopsia. Besides funding from NIH and AGTC, additional early support for this trial came from Achroma Corp, a charitable 501 (c)(3) organization.
Achroma Corp was founded in April of 2012 by Bridget Vissari and her husband, John. As parents of a son, Raymond, affected by achromatopsia, Bridget and John wanted to become a meaningful, useful part of funding the research process. Their organization raises money and awareness in the hopes of one day finding a cure for achromatopsia. “I needed to be able to look [Raymond] in the eyes and know that I am doing everything I am humanly capable of to be able to make options available to him in the future that will afford him the ability to see better,” states Bridget. Since its inception, Achroma Corp. has provided over $152,000 in funding to support achromatopsia research grants. The funding contributes directly to support researcher salaries, clinical trial locations and the purchase of clinical trial equipment. The funding helps equip the research locations with staff and imaging tools necessary to continue the trials and accept more subjects as well as support continued research efforts with gene therapy.
Raymond Vissari (seated), along with AOIP members (left to right) Mara Goldberg, Robert Cooper, and Ryan Johnson. “Dr. Kay, Dr. Carroll, and all of the staff involved have been wonderful with Raymond,” says Bridget.
Besides dollars, the efforts of Achroma Corp have also increased awareness within the achromatopsia community about the importance of research. Without dedicated research volunteers, no prospective treatment could ever make it to market. Raymond and his family exemplify the type of dedication required by these research programs. They participate in research imaging studies 4-5 days every 6 months at two different sites. Though time consuming and sometimes physically and emotionally taxing, the family continues with research in an effort to make their hopes of a cure a reality.
Eight year-old Raymond, who has ACHM, says that being a research participant is “great except for that ERG.” “He has had to push his own limits and complete tasks throughout the trial that are extremely difficult for him, learning that perseverance pays off and that he is capable of more than he may think,” said Raymond’s mother Bridget Vissari. “From my perspective,” Bridget says, “it’s been an adventure for him as well as an opportunity for growth. When I think of all the emotions experienced, all that I’ve learned, and the experience as a whole, I would describe it as a simply amazing journey.”
Participation in clinical trials gives hope for the future
Perhaps more important to the Vissari family is that other people affected by achromatopsia will participate in research studies. “Being a part of something that has great potential to help not only my own son, but so many people affected with MEANINGFUL improvement of their vision is absolutely critical,” says Bridget, “equipment can be bought, salaries of researchers to develop vectors as well as lab costs can be paid for; people to participate in clinical trials necessary for a cure to be fully developed and available, however, cannot. These individuals are priceless. Without them, no further progress can or will be made. To that end, I would encourage others to consider participation in future gene therapy clinical trials with these doctors.” As a result of Raymond’s participation the family now knows that he definitely has cone photoreceptors, when they previously thought he did not. This finding gives the family hope for their son and his future.
This journey demonstrates the dedication and collaboration required for research to succeed. Patients and researchers each play an important role in the research endeavor. In addition, support of foundations like Achroma Corp provide not only critical financial support for research, but raise awareness and help connect researchers with patients with the disease being studied. For more information about the achromatopsia research being done at the AOIP, please contact firstname.lastname@example.org.