The FDA issued a public health advisory February 19th regarding reports of a rare brain infection in people using the psoriasis drug Raptiva. U.S. regulators had received three confirmed reports of a serious brain infection in patients treated with Genentech’s psoriasis drug Raptiva.

According to the FDA, all 4 patients had been taking Raptiva for at least 3 years and had taken no other immunosuppressant drugs. The FDA is advising clinicians to follow patients who are receiving Raptiva closely, as well as those who have discontinued the drug, and to periodically reevaluate whether patients should continue to receive treatment.

The FDA is reviewing the reports of PML in Raptiva users and says it will take appropriate steps to ensure that Raptiva's risks do not outweigh its benefits, that patients prescribed Raptiva are clearly informed of PML's signs and symptoms, and that health care professionals carefully monitor patients on Raptiva and those who have discontinued the drug for any signs of PML. It is caused by a virus that affects the central nervous system. PML symptoms may include unusual weakness, loss of coordination, changes in vision, difficulty speaking, and personality changes.

In a presentation prepared for FDA in 2003, Genentech reported that "ongoing therapy with Raptiva provides extended benefit, with no increase in adverse events as exposure is prolonged." That is a claim that the FDA will likely explore, given that those patients who succumbed to progressive multifocal leukoencephalopathy had been on the medication for at least three years.

Progressive multifocal leukoencephalopathy is considered an opportunistic infection, seen most often in those with compromised immune systems, including cancer and transplant patients and those with AIDS.

Nevertheless Raptiva's removal from the market would have a "very limited impact" on Genentech, a Sanford C. Bernstein analyst told investors. Raptiva is one of Genentech's smallest products, with US sales of $108 million in 2008.