The results led a Food and Drug Administration advisory panel to recommend last month that the agency approve ocriplasmin. And ThromboGenics Inc., the Belgium start-up that sponsored the studies, believes the drug, brand name Jetrea, holds promise for treating other debilitating eye diseases, including age-related macular degeneration and diabetic retinopathy.
"It's exciting and an entirely new approach," Haller said.
The disorder ocriplasmin was tested on, vitreomacular adhesion, involves the vitreous, the clear, jellylike substance in the center of the eyeball.
The jelly contains fibrous proteins that act like a biological glue, keeping the vitreous attached to the back of the eye at vital points, including the optic nerve and the macula, the region of sharpest vision.
By late middle age, however, this glue weakens and the vitreous becomes more watery, causing it to separate from the back of the eye.
This separation is normal and natural.
"The vast majority of people will hardly notice it happen," said ThromboGenics chief executive Patrik De Haes. "You may see a light flare or a floater."
It is only when the separation is incomplete that problems occur. The spot of the vitreous that keeps sticking - the adhesion - can tug on delicate eye structures. As a result, the retina may swell or bleed, the optic nerve's signals to the brain may be disrupted, or the macula may be torn.
Patients often see double or distorted images, like looking in a funhouse mirror, Haller said. If the macula has a hole, they see blank spots - a face with no nose, a word missing letters. Untreated, the complications can lead to blindness.
Surgery to remove the vitreous and substitute saline is the only available treatment. Recovery often requires the patient to lie face downward for a week or more, and serious complications are common.
An estimated 250,000 Americans a year - 850,000 worldwide - ultimately resort to vitreous-removal surgery.
"Currently, we often wait until there is irreversible damage before we operate," Haller said. "If we could safely intervene earlier," vision loss could be prevented.
Ocriplasmin, a concentrated form of a natural enzyme, works by dissolving the biological glue that causes the unwanted adherence of the vitreous to the back of the eye.
Although adhesions went away in only 26.5 percent of eyes injected with the drug, macular holes closed in 40 percent of treated eyes. This suggests that reducing the tugging is helpful, even if the adhesion persists.
"The macular hole closure was an astonishing result," Haller said. "Just getting some slack was apparently enough for the hole to close."
Maureen Kearney, a clinical psychologist in Rockville, Md., noticed vision improvement within hours of the ocriplasmin injection she received at a study site in Lawrenceville, N.J.
"The next day, the newsprint had gone back to the regular size, with no distortion," she recalled. "The missing letters resolved after a month. And there was no down time. The next day I was out and about. Talk about a small miracle."
In stark contrast, she said, a friend had vitreous-removal surgery "and now her eye is nonfunctional."
The ThromboGenics studies found that 18 percent of the ocriplasmin group wound up having surgery, vs. 27 percent with placebo.
The researchers also evaluated the sharpness of patients' vision using standard eye charts. Among patients who started out with poorer vision, a gain of three lines was more likely with ocriplasmin than placebo. But overall, there was no significant difference between the two groups after six months.
Side effects such as eye pain or flashes of light were more common with ocriplasmin (68 percent vs. 54 percent with placebo), but were mostly transient and mild.
The FDA is scheduled to decide whether to approve the drug by Oct. 17. ThromboGenics has not yet set a price for Jetrea, De Haes said.
The company is now testing the drug in patients with macular degeneration - the leading cause of blindness over age 55 - because about a third of them have an adhesion, he said.
Another area of research is diabetic retinopathy, in which tiny blood vessels in the eye grow out of control, impairing vision. Adhesions are believed to contribute to this disease process in many patients, De Haes said.
Contact Marie McCullough
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