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Medical Rounds

A Port for the Storm of AMD

A new implant technology that continuously delivers medication into the eyes is safe and effective in helping to maintain vision and reduces the need for injections in the eyes, according to results of a clinical trial of 220 people with “wet” age-related macular degeneration (AMD).

“Current treatment programs require frequent visits to the doctor, commonly every four to six weeks, for injections of medication. Missed appointments, which are common, can lead to an irreversible decline in vision,” says Wilmer Eye Institute ophthalmologist Peter Campochiaro, who collaborated on the trial with other researchers from Johns Hopkins Medicine, many sites across the country, and Genentech, a biotechnology company. “This study shows that the implant is safe and effective, and may only require a clinic visit and refill every six months.” The researchers published their findings recently in Ophthalmology.

In people with the wet form of AMD, a buildup of debris in the retina triggers the overproduction of vascular endothelial growth factor (VEGF), which stimulates overgrowth of blood vessels that leak, causing swelling and — if untreated — scarring of the retina. The condition is a major cause of blindness in 1.75 million elderly Americans.

Although no therapies are available to cure it, several drugs suppress VEGF and slow the disease progression when injected directly into the eye. The treatments, Campochiaro notes, help preserve central vision but only temporarily, partly because the drugs’ effect is not long lasting. Even monthly injections may show relatively rapid swings in the level of retina swelling due to stopping and then restarting of leakage from blood vessels.

In an effort to keep drug levels steadier, investigators have been testing the value of a port delivery system, a reservoir that is implanted in patients’ eyes through a small incision and slowly releases medication over time. When the reservoir is implanted, physicians can replenish the medication without removing the reservoir.

In the recent clinical trial, researchers found a significant average improvement in the eyesight of the 59 patients who received 100 milligrams per milliliter of medication, and these patients did not require a refill until 15 months after implantation. (Others in the study received 10 and 40 milligrams per milli-liter of medication, and needed refills at 8.7 and 13 months, respectively.) Based on the findings, studies are planned with a larger group of patients receiving implants with a reservoir holding the 100 milligram per milliliter dosage. While the cost of the implant is not yet known, says Campochiaro, over time, it is likely to be less than that of monthly injections, which currently run about $2,000 per injection.

Campochiaro says other treatments that provide sustained suppression of VEGF, such as gene therapy, are also being tested in clinical trials, and results will be available by the end of the year.