ITGAL and progressive multifocal leukoencephalopathy: For example, Efalizumab (Raptiva®, Genentech/Merck Serono), a monoclonal antibody that targets the integrin αL subunit CD11a/LFA1, blocks lymphocyte activation and egress from vasculature; it was approved in 2003 as therapy for moderate to severe plaque psoriasis but was withdrawn from the market in 2009 because of its association with PML and other infections [4].