FDA starts safety review of Roche's CellCept and Novartis' Myfortic after cases of PML

The US Food and Drug Administration is investigating two organ transplant rejection drugs to establish whether they increase the risk of a rare but fatal neurological disease. The agency has initiated a safety review of Roche's immunosuppressant CellCept (mycophenolate mofetil) and Myfortic (mycophenolic acid), made by fellow Swiss drug major Novartis, after 16 reports of progressive multifocal leukoencephalopathy (PML).

PML is a rare disorder that affects the central nervous system. When it occurs, it is usually in patients with immune systems suppressed by disease or medicines. It happens when the polyomavirus, also known as the JC virus, is activated. It is found in most adults but does not usually cause symptoms and scientists do not know exactly how it is activated. However, the awakened virus attacks the cells that make myelin, the protective coating around nerve cells.

Reports of PML led to the withdrawal of the predicted blockbuster multiple sclerosis drug Tysabri (natalizumab; Marketletters passim). US drugmaker Biogen Idec and Irish biotechnology firm Elan pulled the drug from the market in February 2005 when it was linked to three cases of the deadly brain disease. It is now back on the market but with warnings. On the day the safety review was announced, April 10, US shares of Novartis fell 3.8% to $47.31.