A multiple sclerosis (search) drug that was pulled from the market for safety reasons has shown some effectiveness against the painful bowel disorder Crohn's disease (search), researchers say.

Tysabri (search) did not work very well against Crohn's in a short-term study but brought some relief to patients who continued receiving the drug for a year.

The makers of Tysabri halted sales of the drug in February, months after it was approved for MS, because of fears it may be linked to a rare brain disease. Three patients getting Tysabri got the disease and two died.

Elan Corp. PLC and Biogen Idec Inc. recently said a safety review found no new confirmed cases of the brain disease in patients treated with Tysabri. They are seeking government approval to resume selling the drug, also called natalizumab.

An estimated 500,000 Americans are afflicted with Crohn's disease. The cause is unknown and there is no cure. Symptoms include abdominal pain, persistent diarrhea and fever. Drugs to control inflammation and suppress the immune system can bring some relief. Tysabri attaches to the immune cells and prevents them from reaching areas of inflammation.

In Thursday's New England Journal of Medicine, researchers reported the results of two company-funded international studies of Tysabri for Crohn's.

In the first test, 905 patients got three infusions of Tysabri or a dummy infusion over eight weeks. The two groups had similar rates of response and remission.

In the second study, 339 patients from the first test who had improved with Tysabri were given either the drug or a dummy infusion every four weeks for a year. Those who got the Tysabri had higher rates of sustained response (61 percent vs. 28 percent) and remission (44 percent vs. 26 percent).

Elan's Dr. Lars Ekman said the drug has now been tested in 1,500 Crohn's patients, including those in another yet-unreleased positive trial.

"We remain very confident that Tysabri will be made available over time as a treatment alternative in Crohn's," he said.

In an accompanying editorial, Dr. Daniel Podolsky of Massachusetts General Hospital said not enough is known yet about Tysabri's effectiveness against Crohn's to determine whether the drug is worth the risks.

Dr. Ellen J. Scherl of Weill Medical College of Cornell University, who had patients in the first study, said the research identified some types of patients who may benefit most from Tysabri.

"It would be a loss for us not to have this as an option for patients," she said.