Elan and Biogen Idec are to appeal a decision by European regulators not to recommend approval of their embattled multiple sclerosis drug Tysabri for the treatment of Crohn’s disease.

The European Medicines Agency’s Committee for Medicinal Products for Human Use said that the benefits of using the drug in this setting did not outweigh the risks, and there was “insufficient evidence” of its effectiveness as a therapy for the disease. Moreover, it voiced concerns over potentially serious side effects, including the brain infection progressive multifocal leukoencephalopathy (PML).

Tysabri (natalizumab) was approved in the USA for the treatment of multiple sclerosis at the end of 2004, but was promptly taken off the shelves again in March 2005 after a patient died from PML while taking Tysabri. It remerged in July last year after receiving clearance, with certain restrictions, from regulators on both sides of the Atlantic.

The companies said they will appealing the CHMP’s decision to reject its use in Crohn’s, and expect a verdict in the first quarter of next year.

“Without natalizumab, European patients with severely active disease who failed other therapies and who are suffering from continuous symptoms may be offered surgery, with its potential complications, intravenous nutritional therapies or clinical trials with unproven experimental agents, depending upon on the patients' condition,” commented Professor Jean-Frederick Colombel, University of Lille. “There is a need for new therapies for this very difficult disease.”

Shares dip

Shares of Elan closed down 3.3% to $21.19 on the New York Stock Exchange yesterday, but while Biogen Idec’s stock dipped almost 2% during the day, it recovered again to finish just $0.16 off the previous day’s close.

The US Food and Drug Administration is holding an advisory committee meeting to discuss the application on July 31, 2007, so all eyes will be on their decision now.