New Medication Slows Rare Kidney Disease

By Steven Reinberg
HealthDay Reporter

WEDNESDAY, June 6 (HealthDay News)- Researchers say a drug called eprodisate can slow a rare but toxic buildup of amyloid protein that results in end-stage kidney disease.

While not a cure for the condition, called amyloid A amyloidosis, the drug can delay the need for kidney dialysis, according to the report in the June 7 issue of The New England Journal of Medicine.

"AA amyloidosis is a rare disease that occurs in some individuals who have long-standing inflammatory conditions such as rheumatoid arthritis," explained lead author Dr. Laura M. Dember, an assistant professor of medicine at Boston University. "The diseases cause amyloid deposits to form in the kidney, which results in progressive deterioration of renal [kidney] function and ultimately progression to end-stage renal disease," she explained.

About 3,000 people a year in the United States develop AA amyloidosis.

To date, there has been no treatment for the disease other than trying to treat the underlying inflammation, Dember said. "In many individuals, that is ineffective," she said.

Eprodisate is a new drug that targets the formation of amyloid. "We found that patients treated with eprodisate had a slower rate of decline in kidney function than did the patients treated with placebo," she said.

In the study, Dember's team randomly assigned 183 patients around the world with AA amyloidosis to treatment with eprodisate or placebo.

After two years of therapy, 24 of the 89 patients taking eprodisate experienced a worsening of their condition compared with 38 of the 94 patients receiving placebo.

The way the drug works can potentially be used to treat other diseases, such as other forms of amyloidosis and Alzheimer's disease, Dember said.

One expert believes the drug is promising.

"For the first time, there is a drug that prevents the development of amyloid," said Dr. S. Vincent Rajkumar, a professor of medicine at the Mayo Clinic and co-author of an accompanying journal editorial. "But it is very hard to generalize these results to other types of amyloidosis," he said.

Eprodisate didn't prevent patients from the need for dialysis, Rajkumar noted. "On the other hand, it did slow down the progression of the disease," he said. "That means that patients can live for a longer time with their own kidneys."

Another study in the same journal issue looked at how AA amyloidosis developed in 374 patients who were followed for an average of 86 months.

In this study, researchers from the Royal Free and University College Medical School, London, led by Dr. Helen Lachmann, found that those with the diseases lived an average of 133 months. Most importantly, disease prognosis was closely linked to the amount of amyloid A protein in the blood.

For patients with the highest concentrations of amyloid A protein, the risk of death was 17.7 times higher compared to those with the lowest concentration of amyloid A protein, Lachmann's group found.

Patients whose amyloid A protein concentrations were reduced lived longer than patients whose levels remained constant, the researchers added.

"In the present study, decreased production of amyloid A protein was associated with a favorable [kidney] outcome, stabilization or regression of amyloid deposits and prolonged survival," the researchers concluded.

SOURCES: Laura M. Dember, M.D., assistant professor, medicine, Boston University; S. Vincent Rajkumar, M.D., professor of medicine, Mayo Clinic, Rochester, Minn.; June 6, 2007, The New England Journal of Medicine

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