Stream of new treatments not expected to fill the void soon

The pipeline of experimental drugs to treat multiple sclerosis looks promising, but nothing that might take Tysabri's place as a treatment will go on sale for years.

That's true even for some of the most talked-about therapies such as Aimspro, made by Britain's Daval International Ltd. from goat's blood serum, and Campath, a leukemia treatment from Genzyme Corp. of Cambridge.

Though several older MS drugs remain on the market, many doctors and patients hope Tysabri, made by Biogen Idec Inc., will prove safe enough to resume sales soon despite last week's disclosure of the death of a patient in a clinical trial.

''This one looked so good, it's definitely a letdown," said Peter N. Riskind, professor of clinical neurology at the University of Massachusetts Medical School who has done Tysabri research. If Tysabri stays off the market, ''it will certainly leave a hole."

Mark Enyedy, senior vice president at Genzyme, said the company just enrolled 330 MS patients in a clinical trial of Campath. But the drug isn't likely to be approved to treat MS until 2007 at the earliest, he said.

''As far as new agents becoming available, I think there will be a bit of a lull," he said.

Current treatments for MS include Biogen's previous drug Avonex, and Rebif, which is made by Switzerland's Serono SA, whose US headquarters are in Rockland. The two are different doses of essentially the same protein, which helps the immune system fight against inflammation.

The National Multiple Sclerosis Society in New York counts 160 clinical trials now underway. The large number reflects how the field of immune-system research has grown with interest in AIDS.

The society doesn't break down exactly which companies are working on which MS drugs. But the society's director of biomedical research, Patricia O' Looney, says she divides the most promising areas of research into four main areas including combination therapies that mix current treatments like Avonex with non-MS treatments; ''immunoregulator" therapies that kill off T cells; hormonal treatments based on the observation that MS symptoms tend to fade in pregnant women; and the use of statin-lowering cholesterol drugs.

Even though these treatments are all years from commercialization, she said, together they should make patients optimistic that new treatments will arrive eventually. ''There's obviously a disappointment with Tysabri, but the pipeline isn't thin," she said.

Many MS patients passionately follow news about drug development. ''Keep the faith," went one message posted on thisisms.com. ''But it does get harder when it seems that for every one step forward we take two steps back."

Ross Kerber can be reached at kerber@globe.com.