Genentech Inc. said Wednesday it is withdrawing psoriasis drug Raptiva from the U.S. market because of an increased risk of progressive multifocal leukoencephalopathy, a rare and usually fatal disease of the central nervous system.The move comes nearly two months after South San Francisco-based Genentech -- a wholly owned subsidiary of Swiss drugmaker Roche since March 26 -- after the Food and Drug Administration issued a warning about Raptiva’s connection to PML.The FDA approved Raptiva in 2003.

Regulators in Europe, where the drug has been distributed by Merck Serono, in February recommended pulling the drug off shelves. Canada also has halted sales of the drug. PML is a rare, progressive neurologic disease caused by a virus that affects the central nervous system. It typically occurs in people whose immune systems have been severely weakened. There is no known treatment.Genentech estimates that approximately 2,000 patients in the United States may currently be receiving Raptiva for chronic plaque psoriasis. Since FDA approval in 2003, approximately 46,000 patients worldwide have been treated with Raptiva.

Learn more about dangerous Raptiva side effects.