Genentech has warned doctors that a patient being treated with its psoriasis drug Raptiva has developed a rare brain infection, a month after another person taking Rituxan died from the same disease.

The US biotechnology company has issued a Dear Healthcare Provider letter to inform potential prescribers of a case of progressive multifocal leukoencephalopathy in a 70-year old patient who had received Raptiva (efalizumab) for more than four years for treatment of chronic plaque psoriasis. Genentech said it will work with the US Food and Drug Administration to update the prescribing information for Raptiva “and determine if further action is needed”.

Genentech said the case was reported to the company in late September as part of its ongoing safety monitoring and surveillance programme. The firm added that “based on the medical information available to date, Raptiva may have had a contributory role in the development of PML in this patient.”

It was also noted that there are no other cases of confirmed PML in patients treated with the drug but there has been a report of a 62-year-old patient on Raptiva who developed progressive neurologic symptoms and died of an unknown cause. Genentech added that it is important for patients not to change or stop treatment without first talking with their doctor.

Licensing partner Merck Serono said it has informed regulatory acencies outside the USA and Japan “about this serious adverse event” and is working with the European Medicines Agency and other regulators to update the product information”. The firm’s chief medical officer Guy Braunstein noted that “although this appears to be an isolated case among more than 46,000 patients treated with Raptiva, we want to ensure investigators and prescribers are made aware, so that they can make informed treatment decisions”.

Last month Genentech and partner Biogen Idec told doctors that a patient with rheumatoid arthritis who took Rituxan (rituximab) had died after developing PML.