WASHINGTON ( CNN ) -- The government is warning that taking the psoriasis drug Raptiva could result in serious brain infection and even death . Raptiva may cause a serious brain infection called progressive multifocal leukoencephalopathy . The Food and Drug Administration cited three confirmed cases , and a possible fourth , of people diagnosed with progressive multifocal leukoencephalopathy ( PML ) after being treated with Raptiva . `` Three of those patients have died , '' the FDA said in a public health advisory . `` All four patients were treated with the drug for more than three years . '' None was receiving other treatments that suppress the immune system . Raptiva 's product labeling was revised in October to highlight a boxed warning about the risks of life-threatening infections , including PML . `` At that time , the FDA directed Genentech , the manufacturer , to develop a risk evaluation and mitigation strategy ( REMS ) to include a medication guide to educate patients about the drug 's risks , '' the FDA 's advisory says . In the advisory , issued Thursday , the FDA highlighted the confirmed cases and promised to `` take appropriate steps '' to ensure that Raptiva 's risks do not outweigh its benefits . The FDA also said it will ensure that patients `` are clearly informed of the signs and symptoms of PML '' and that health care professionals `` carefully monitor patients for the possible development of PML . '' Overseas , the European Medicines Agency has gone further , recommending that no new prescriptions for Raptiva be issued and that patients taking the drug talk to their doctors about an alternative . On Thursday it asked the European Commission to make that recommendation legally binding . The group 's Committee for Medicinal Products for Human Use determined `` that the benefits of Raptiva no longer outweigh its risks , because of safety concerns , including the occurrence of progressive multifocal leukoencephalopathy in patients taking the medicine . '' It said patients who have been treated with the drug should be `` closely monitored for neurological symptoms and symptoms of infection . '' `` Patients who are currently taking Raptiva should not stop treatment abruptly , but should make an appointment with their doctor to discuss the most appropriate replacement treatment , '' the agency said . Raptiva , a once-weekly injection for adults with moderate to severe plaque psoriasis , works by suppressing T-cells -- cells that help fight infection -- in the immune system . Those cells cause the skin inflammation associated with psoriasis . By suppressing T-cells , Raptiva `` decreases the function of the immune system , which increases a patient 's susceptibility to infections , '' the FDA said . The National Institutes of Health says the prognosis for PML `` remains grim ; the disease usually lasts for months and 80 percent die within the first six months , although spontaneous improvement has been reported . Those who survive PML can be left with severe neurological disabilities . '' Around 6 million to 7 million Americans have psoriasis , which is incurable , the NIH says .
NEW : European Medicines Agency discourages new Raptiva prescriptions . Raptiva 's product labeling was revised in October to highlight risks . Raptiva is an injection for adults with moderate to severe plaque psoriasis . The drug suppresses T-cells , which makes it decrease immune system function .