Rituxan, a cancer drug by Genentech and Biogen Idec, did not slow the disabling effects of the most difficult form of multiple sclerosis in clinical trials conducted over a period of almost two years, according to the two companies.

If the drug had succeeded, it would have been the first to work against the primary progressive form of multiple sclerosis.

?While the primary results are not what we had hoped, we continue to believe in the potential of B cell therapy for patients living with MS,? said Michael Panzara, Biogen?s vice president and chief medical officer of its neurology strategic business unit.

The Rituxan approach of killing inflammatory B cells is different than that of currently approved MS drugs.

The drug makers indicate they will continue to analyze the results of these trials.

Source: Bloomberg News, ?Drug Fails to Slow Nerve Damage,? April 15, 2008.