New drug helps close macular holes.

A drug that improves on the current approach to treating macular holes, a disorder that can result in severe loss of vision, shows increasing promise in patient trials.

The drug consists of TGF-[beta.sup.2], a growth factor protein that plays a key role in healing wounds. Originally derived from cow bones, the substance can now be made in the laboratory to better meet the increasing demand, says Ann Hanham, medical director of Celtrix Pharmaceuicals in Santa Clara, Calif., the company that developed it.

In the early 1990s, Bert M. Glaser and his colleagues at St. Joseph Hospital in Baltimore tested the growth factor for the first time in humans. Vision improved in 10 of the 11 patients who received the highest dose. They could see at least two additional lines on a standard eye chart, Glaser's group reported in the July 1992 OPHTHALMOLOGY. In a separate study, about half the patients undergoing traditional surgery for macular holes had improved vision, compared to over three-quarters of patients receiving the new treatment, says Hanham.

Within a month, researchers at three hospitals will finish enrolling patients for a final efficacy trial. In that study, surgeons will use either the new drug treatment or the standard procedure on 120 volunteers and will follow the patients for 12 months. This is the first trial to employ a recombinant form of the growth factor, rTGF-[beta.sup.2].

The study is taking place at the University of Miami School of Medicine, the Beaumont Hospital in Royal Oak, Mich., and St. Joseph Hospital.

In response to the Food and Drug Administration's recommendation to meet patients' demands for the new treatment, Celtrix has applied to FDA to begin selling the drug this fall -- after it sees the initial results from the current study, yet before FDA approves fullscale commercialization of the product, says Hanham. The company would provide the drug to about 500 additional patients at the three centers. Celtrix also hopes to distribute the growth factor to seven more centers by 1995.

So far, approximately 700 people have received the drug as part of various safety and efficacy studies, says Hanham, who addressed a conference on clinical trials organized by BIO/TECHNOLOGY magazine last week.

Glaser and his colleagues are also enrolling volunteers for a study investigating whether the growth factor can help treat the much more common agerelated macular degeneration.

Macular holes occur in fewer than 10,000 people each year, primarily 50- to 70-year-olds, and usually are the result of aging. An eye injury, such as getting smacked with a baseball, can also create a hole.

The hole "results in a very distinct anatomic change" and leaves individuals unable to read or drive, Hanham explains. It normally occurs when the eye's vitreum shrinks and pulls away from the retina. Pockets form around the hole and under the retina, collecting fluid and creating "quite a severe loss of vision," she says.

Normally, surgeons simply remove the vitreum to prevent it from pulling on the retina and replace it witha gas bubble, which eventually fills with natural fluids.

The new approach involves these same procedures, but physicians drip growth factor on the hole to encourage healing. The protein forms fibrous tissue, heals the hole, and seals the edges of the retina, Hanham explains. However, surgery on the vitreum usually results in cataracts, which can be removed.

If the FDA approves the product for sale, "it's going to be expensive," Hanham acknowledges.