The pharmaceutical giant Genzyme has started a clinical trial to see whether a drug to treat macular generation could be delivered via long-lasting gene therapy rather than monthly injections.

A drug called Lucentis, made by Genetech, has proved effective at treating the wet form of age-related macular degeneration, which can lead to blindness. Some 200,000 Americans a year are diagnosed with the disease. But Lucentis has to be injected into the eye every month or two, a burden for patients and doctors.

Lucentis binds to and neutralizes a wound-healing growth factor known as VEGF. This binding action stalls the excess growth of blood vessels in the eye that characterizes age-related macular degeneration. Genzyme's gene therapy drug, officially called AAV2-sFLT01, would insinuate itself into the patient's retinal cell to produce the same VEGF-binding protein as Lucentis over far longer periods--up to several years.

A phase 1 clinical trial of Genzyme's gene therapy treatment began at the end of May. Three patients received the treatment, according to Sam Wadsworth, a Genzyme group vice president in charge of gene and cell therapy. Preliminary results should be available in about a year.

The trial is one of a handful worldwide seeking to prove the effectiveness of gene therapy for eye diseases. The Genzyme trial also involves using new type of virus as the delivery mechanism. Early results of a federally funded trial to deliver normal-functioning genes to patients with a rare retinal disease known as type 2 leber congenital amaurosis, or LCA, have confirmed that this "viral vector" has merit for eye treatments, several researchers say.

The LCA trials "demonstrated success both in terms of safety and ability to introduce the gene and have efficacy and success," said Jeffrey S. Heier, an assistant professor at Tufts University School of Medicine and director of retinal research at Ophthalmic Consultants of Boston, a private practice group, who is involved in the Genzyme research. "This study is taking the virus vector that they used, and [Genzyme has] taken what has really been the success of the anti-VEGF story and they've packaged the two together."

Eyes have been an early target for gene therapy because they are small--meaning they require relatively little active dose, they are self-contained, and because the tools of eye surgery have advanced enough to make the treatments possible. The drug has to be delivered to the retina, a thin film lining the inner wall of the eye. Instrumentation has improved in recent years to allow injections through the retina without piercing it, said Shalesh Kaushal, chairman of ophthalmology at University of Massachusetts Memorial Medical Center and UMass Medical School.