Panel Backs Marketing of New Drug to Treat MS : Medicine: FDA approval is expected to follow. Beta-interferon could be available to those with the disabling disease by summer.

A Food and Drug Administration advisory board Friday recommended marketing approval for beta-interferon for the treatment of multiple sclerosis, a disabling disorder that affects as many 350,000 Americans.

“This is a big step because there is no other drug that is effective in treating the disease,” said Abe Eastwood, director of research and grants programs for the National Multiple Sclerosis Society. “If you have something that will improve the quality of life for this many people, you have to be very enthusiastic.”

The drug, trade-named Betaseron, could be available to patients early this summer, according to the FDA and the drug’s distributor, Berlex Laboratories of Richmond, Calif. Betaseron must still be formally approved by the FDA, but the agency usually follows the recommendations of its advisory committee, which met in Rockville, Md.

The approval marked the second day in a row that the panel approved a new drug for a previously untreatable condition. On Thursday, it recommended approval of the first drug that can retard the progression of Alzheimer’s disease.

Several researchers presented unpublished evidence to the panel indicating that MS patients treated with beta-interferon suffer fewer flare-ups of the disease and that the attacks that do occur are less severe. The evidence also suggested, but did not prove, that the drug delayed the progression of the disease.

“I thought there was at least enough . . . evidence for the drug to be used for multiple sclerosis,” said Dr. Sid Gilman, a panel member who is a neurologist at the University of Michigan at Ann Arbor.

But the recommendation was not unanimous. Two of the panel’s nine members voted against approval.

“I felt there was insufficient evidence to meet the standards that the committee has applied to other drugs,” said one of the dissidents, Dr. Nancy Tempkin, a neurologist at the University of Washington.

Beta-interferon is the first drug designed to impede progression of the disease. Physicians now use steroids to decrease the duration of MS flare-ups and other drugs to ameliorate some symptoms of the disease, “but there is no other drug that is effective all during the course of the disease,” Eastwood said.

Multiple sclerosis is a progressive, often disabling disease of the central nervous produced when , for reasons still unknown, the body’s immune system attacks the protective myelin sheaths surrounding nerve fibers. The process is much like scraping the insulation off an electrical wire, short-circuiting the transmission of nerve impulses that control muscle activity.

MS patients can suffer loss of balance and muscle coordination, blurred vision and slurred speech, difficulties in walking and even paralysis in severe cases. MS affects twice as many women as men, and two-thirds of all cases develop when the victim is between the ages of 20 and 40.

The new drug was tested in a subgroup of patients with so-called exacerbating-remitting MS. This condition , which accounts for about 30% of all MS patients symptoms subside totally or partially after a flare-up. The flare-ups are followed by periods of stability that can last months or years. In the more common form of the disease, the symptoms gradually worsen.

Beta-interferon, produced by Chiron Corp. of Emeryville, Calif., is a genetically engineered form of a naturally occurring immune protein. Scientists speculate that it blocks the activity of white blood cells that attack myelin.

The new study involved 338 MS patients in the United States and Canada. One-third injected themselves with high doses of beta-interferon every other day for two years, one-third injected lower doses and the remaining third injected a placebo.

According to Dr. Kenneth Johnson, a neurologist at the University of Maryland, patients receiving the highest doses of beta-interferon had 35% fewer flare-ups and 50% fewer severe flare-ups than those on placebos. The average time between flare-ups rose from 153 days for those on placebos to 295 days for those receiving the high doses. Those who received the drug also had less need for hospitalization and for steroids to treat relapses, he said.

Dr. Donald Paty, a neurologist at the University of British Columbia, used magnetic resonance imaging to study brain lesions in the patients. He told the panel that the lesions in 48% of those who took the drug were smaller at the end of the trial, compared with only 23% in those who received placebo.