Elan Corp and Biogen Idec have received some more good news about Tysabri as US regulators have decreed that the multiple sclerosis drug can now also be used to treat Crohn's disease.

The firms announced the approval of a supplemental Biologics License Application by the US Food and Drug Administration for Tysabri (natalizumab) which has been given the green light as a treatment for moderate-to-severe Crohn's disease in patients who have failed or cannot tolerate available therapies. The drug will be available by the end of February, upon the completion of “key implementation activities related to the approved risk management plan”.

Elan noted that the approval is accompanied by “robust labelling with safety warnings”, which is designed to minimise potential risk of progressive multifocal leukoencephalopathy, a brain infection. The PML risk plays a major part in the history of the compound as Tysabri, which was approved for MS at the end of 2004, was taken off the shelves again in March 2005 after a patient died from the condition. It remerged in July 2006 after receiving clearance, with certain restrictions, from regulators on both sides of the Atlantic.

Those restrictions saw Elan and Biogen introduce a risk management plan and a similar mandatory prescribing programme will be in place for the Crohn’s indication.

Evan Beckman, senior vice president of immunology R&D at Biogen Idec, said the firms are pleased with the FDA's decision. He noted that “despite the therapeutic advances of the anti-tumour necrosis factor therapies” used to treat the disease, such as Abbott’s Humira (adalimumab) and Johnson & Johnson/Schering-Plough’s Remicade (infliximab), “there remains a significant unmet need for Crohn's patients who have inadequate responses to, or are unable to tolerate, current CD therapies”.

Particularly pleasing for Elan and Biogen is that the US approval comes just after they failed in their bid to get a positive recommendation from Europe’s regulators for Tysabri in Crohn’s disease. That decision came after an appeal the companies filed following a previous thumbs-down off the Committee for Medicinal Products for Human Use in 2007 over safety concerns.