Biotechs Wage Genetic War on Blindness, Macular Degeneration
Two US companies are jockeying for the early lead in gene therapy for the eye, treatment that could prevent as many as 3.6 million seniors from going blind in the states.
The companies are testing separate technologies to stop the progression of age-related macular degeneration, a possible multibillion-dollar market, they say. AMD is the leading cause of blindness among Americans older than 60 and there are no cures, according to the National Eye Institute in Bethesda. It affects nearly 30 percent of people older than 75. Surgical and pharmaceutical treatments have had very limited success, the institute says. The disease causes dead cells and blood vessels to block out the macula, a central function of vision in the back of the eyeball.
Gene therapy for AMD became more feasible last year when several research teams supported with the eye institute grants discovered that the disease is linked to certain genes. The technologies being developed are based on injecting into the eye a gene that is hitched to a vector, a harmless virus. The vector used disarmed version of an adenovirus, a family of viruses that in virulent forms cause a number of human maladies from eye infections to diarrhea. This vector carries a gene to cells in the back of the eye to alleviate some blockage of the macula.
Last week, a company announced it had completed enrollment in a clinical study of its gene therapy method in patients recently diagnosed with the severe stage of the disease, called wet ADM, in which unwanted blood vessels and pockets of fluid block the macula. The study will be conducted at nine eye institute-supported clinics across the country, including Johns Hopkins Medical Center in Baltimore. There are 200,000 new cases of wet AMD each year and the 1.2 million cases in the United States are expected to triple in the next 20 years as baby boomers age, the institute says.
GenVec's phase 1 trial follows successful tests on 28 patients, results of which were published last month in the journal Human Gene Therapy Patients in the study showed that progression of the disease might be halted for six to 12 months after a single treatment.
"We like GenVec's approach very much," said Navdeep S. Jaikaria, managing director and senior biotech analyst for Rodman & Renshaw LLC of NewYork.
"Even though there are new drugs coming into the market, this is a chronic disease that will not respond to any magic bullet," Jaikaria said. "The beauty of this is that with one injection, they have shown in preliminary work that it could stabilize the disease. I think it is important because it could then be used in combination therapies and at the very least used for late-state AMD therapy."
Advanced Vision's method, successful in animal studies, could have a therapeutic effect lasting for years, according to Sheila Connelly, the company's vice president for development. The company is also cooperating with leading eye researchers at Johns Hopkins.
The technology consists of injecting a substance called AVT-1 into the eyeball on a virus derived from cattle, called a lentivirus. Once into the eye, the substance becomes part of the DNA of cells to induce them to secrete more of a natural compound called kininostatin that, in turn, diffuses throughout the eye and blocks the growth of the new blood vessels. The delivery of kininostatin is continuous, Connelly said.
Advanced Vision, which is also working on treatments for two other eye diseases, retinitis pigmentosa and diabetic proliferative retinopathy, has so far supported its preclinical studies in gene therapy with Small Business Innovation Research grants through the eye institute.
Regardless of whose AMD gene therapy clears clinical trials first, the Food and Drug Administration will face "some difficult and new challenges to approve its use," said Jeffrey W Church, GenVec's CFO. His view is shared by Malcolm Moos, FDA medical officer for the agency's Center for Biologics Evaluation and Research.
"Although a long-lasting therapy is of great benefit in treating chronic genetic diseases, it requires new evaluation criteria and ever more vigilant oversight during the experimental, clinical trial phases of research," Moss said at a 2003 joint meeting of FDA and eye institute officials discussing retinal gene therapy. "For these reasons, gene therapy clinical trials present the FDA with largely uncharted regulatory challenges."
Karl Csaky, chief of the eye institute's retinal diseases and therapeutics research, thinks the future of the AMD gene therapies should be discernible soon. "We will know within a year if there are any major problems, or within five years if there are any benefits," Csaky said.
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