依法利珠单抗（Efalizumab，药品商品名为 Raptiva，瑞体肤，默克）是牛皮癣的治疗用药，是一种抗CD11a的单株抗体制剂，其作用机制是辨识白血球上的CD11a抗原，使白血球与其他细胞附着的能力降低，抑制其免疫作用。

因为依法利珠单抗会抑制免疫系统，所以其引发的副作用包括细菌性败血症、病毒性脑膜炎，真菌性疾病，或因再活化的潜伏性JC病毒引发渐进性多病灶脑白质病(Progressive multifocal leukoencephalopathy, PML)。

因为此药有产生渐进性多病灶脑白质病的风险，欧洲药品管理局(European Medicines Agency)于2009年2月提议，应暂停依法利珠单抗在欧盟贩售。

Efalizumab (trade name Raptiva, Genentech, Merck Serono) is a formerly available medication designed to treat autoimmune diseases, originally marketed to treat psoriasis. As implied by the suffix -zumab, it is a recombinant humanized monoclonal antibody administered once weekly by subcutaneous injection. Efalizumab binds to the CD11a subunit of lymphocyte function-associated antigen 1 and acts as an immunosuppressant by inhibiting lymphocyte activation and cell migration out of blood vessels into tissues. Efalizumab was associated with fatal brain infections and was withdrawn from the market in 2009.