"New clinical trial results show that a leukemia drug offers a promising prospect for treating multiple sclerosis, but the drug's side effects prompted its sponsors to suspend dosing in the clinical trial while they discuss the next step with the Food and Drug Administration.

The drug is called Campath, and it is now approved in the U.S. for treating B-cell chronic lymphocytic leukemia. Campath is being developed for multiple uses by Genzyme. The companies said they will "work closely" with regulators and clinical investigators "to ensure that a comprehensive approach is in place to manage patient safety."

Friday's announcement offers a complicated good news/bad news scenario for the treatment of multiple sclerosis.

The companies preferred to focus on the positive news. "Based on these results, we will be moving this program forward with a tremendous sense of urgency," said Henri A. Termeer, chairman and CEO of Genzyme.

The latest test results come from a phase II (midstage) clinical trial. In order to secure FDA approval, the companies must conduct a bigger, more extensive phase III trial, and they must design a study that takes into account the safety issues that have been identified.

The red flag was the comparison of "serious adverse events" between MS drug Rebif, which had two, and Campath, which had nine. Among the Campath patients, three suffered from a disease, nicknamed ITP, that can cause abnormal bleeding due to low blood-platelet counts. Two of these patients received high doses of Campath, and one received a low dose. One patient died.

The companies said most patients had received a second year's worth of doses in a planned three-year study. The companies said they would evaluate "the necessity and timing of the third planned dose," adding that they are talking to the FDA "about what additional steps might be needed to protect patient safety."

The companies said they will continue to collect efficacy and safety date from the trial while they plan for a phase III trial.

The encouraging news from the phase II interim results shows that Campath patients had significantly fewer relapses of MS "after at least one year of follow-up" vs. Rebif patients. Schering and Genzyme said the comparison was statistically significant for both high doses and low doses of Campath, whose patients experienced at least a 75% reduction in relapse risk vs. Rebif patients.

However, the companies said there was no difference in effectiveness between the high dose and the low dose, so they will no longer test the high dose. In addition, Campath patients failed to achieve a statistically significant improvement vs. Rebif patients in another indicator of efficacy called "risk for progression of clinically significant disability."


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