The first oral drugs — cladribine and fingolimod — may soon be available for treatment of multiple sclerosis. All current drugs used to treat the disease are taken by injection.

In three separate clinical trials, the new drugs significantly lowered the relapse rate of the disease.

Treatment seeks to minimize relapses and slow or eliminate disease progression.

Multiple sclerosis (MS) is a disease that usually appears in young adulthood. It's caused by destruction in the brain and spinal cord of the myelin that coats nerves. Myelin acts as an insulator around the nerves, much like the insulation around the electrical wires in a house.

Destruction of myelin disrupts communication between the brain and other parts of the body. Disease symptoms and severity vary widely, depending on which nerves are affected and how much myelin is destroyed. In extreme cases, MS can cause partial or complete paralysis.

Many MS sufferers have periods with little or no disease symptoms followed by periods of attacks (relapses). The disease often becomes more disabling over time (progression). At present, there is no cure for MS. Treatment seeks to minimize relapses and slow or eliminate disease progression.

All three trials involved over 1,000 subjects. Two tested fingolimod, one against a placebo for two years, the other against an injectable interferon for one year. The third study tested cladribine versus placebo for two years. In all three studies, the oral drug lowered the number of relapses seen. Both cladribine and fingolimod lowered the rate of disease progression significantly more than placebo did. Fingolimod and interferon takers had similar rates of disease progression.

The observed annual relapse rates were 16−20% with fingolimod vs. 33% with interferon, 16−18% with fingolimod vs. 40% with placebo and 14−15% with cladribine vs. 33% with placebo.

What makes the results with cladribine particularly encouraging is that patients took the medication in only two or four courses of four to five days each per year. That's 8−20 days of treatment in a year. Fingolimod was taken daily in both of its studies.

MS is thought to be an autoimmune disease, a disease where the body's immune system mistakenly attacks part of itself, here myelin, as an invader. Both of the new drugs work by suppressing part of the immune system. In general, immunosuppressant drugs have many drawbacks, one of which is that people who take them become much more susceptible to infections.

The recent trials specifically found problems with new and reactivation of old herpes zoster (shingles) infections in subjects taking either of the oral drugs. The authors of all three trials point out that the risks of taking these new drugs will need to be balanced against their possible benefits on a patient by patient basis. But the new drugs will offer MS sufferers options that have not previously existed.

The manufacturers of both drugs are currently seeking FDA approval for the medications.

The results of all three trials appear in the February 4, 2010 issue of the New England Journal of Medicine.