Genentech, the company that makes Raptiva (efalizumab) to treat psoriasis, recently announced it has begun a voluntary, phased withdrawal of the drug from the U.S. market because it has the potential to cause progressive multifocal leukoencephalopathy (PML), a rare, progressive neurological disease that’s usually fatal. By June 8, 2009 Raptiva will not be available in the United States.

The drug is not being withdrawn immediately to give physicians and patients taking Raptiva time to safely and appropriately discontinue treatment. Because it’s possible that abruptly discontinuing Raptiva may cause a severe flare of psoriasis, it is very important that patients work with their physician to taper the medication instead of stopping it abruptly.

PML is a disease of the central nervous system caused by activation of the John Cunningham (JC) virus. The JC virus causes an infection without symptoms in childhood and 86% of adults have antibodies.

In most people the JC virus is latent in the kidneys and parts of the immune system. But in people who are severely immunocompromised, the virus can reactivate, travel to the brain, and infect the cells that make myelin, an insulating sheath that surrounds nerves and is essential for proper functioning of the nervous system. The median survival time for people with PML, without HIV infection, is 2.6 months.

According to Genentech, there have been 3 cases of PML in people who were taking Raptiva. Another patient who was treated with Raptiva developed progressive neurologic symptoms and died of unknown causes.