Efalizumab (trade name Raptiva) is a medication designed to treat psoriasis. As its name implies, it is a recombinant humanized monoclonal antibody that binds to CD11a and acts as an immunosuppressant. It is administered once weekly by subcutaneous injection. It acts to inhibit white blood cell migration out of blood vessels into tissues. Because it suppresses the immune system, it has been associated with fatal brain infections, and has been withdrawn from the market.

Known side effects include bacterial sepsis, viral meningitis, invasive fungal disease and progressive multifocal leukoencephalopathy, a brain infection caused by reactivation of latent JC virus infection.