Tysabri Getting More Scrutiny Over Brain InfectionOct 26, 2009 | Parker Waichman LLP
European regulators are taking another look at Tysabri. According to The Wall Street Journal, the European Medicines Agency's Committee for Medicinal Products for Human Use (CHMP) is concerned that Tysabri may have a higher rate of a rare brain infection called progressive multifocal leukoencephalopathy, or PML, than previously disclosed.
According to the Journal, Tysabri is seen as one of the most effective MS treatments on the market, especially for those with severe cases who have few other options. In the U.S. Tysabri was taken off the market in 2005 after three patients in clinical trials developed PML. But the drug was reapproved in 2006, although it was subject to restrictions. Tysabri is now available only to patients with relapsing multiple sclerosis (MS) or Crohn’s disease (CD) who are enrolled in the risk minimization plan called the TOUCH Prescribing Program. Under the TOUCH Prescribing Program, every Tysabri-treated patient is closely monitored and followed for the occurrence of PML and other serious opportunistic infections.
PML attacks the brain and central nervous system and is usually fatal. It is caused by a polyomavirus, called the JC virus. The JC virus is often acquired during childhood. Most adults have been infected with the JC virus but do not develop PML. The virus appears to remain inactive until something (such as a weakened immune system) allows it to be reactivated and start to multiply. Symptoms include vision problems, loss of coordination, and memory loss. Patients who survive the disease are often permanently disabled.
According to The Wall Street Journal, CHMP has reported 23 cases of PML among Tysabri patients since the. The U.S. Food & Drug Administration (FDA) confirmed this number, the Journal said, and added that those cases occurred after Tysabri returned to the market in 2006. Previously, that number stood at 13.
CHMP's Tysabri review will discuss "any additional measures necessary to ensure the safe use of Tysabri and how to balance the risks to the patients against the benefits of the treatment," the Journal said.
In September we reported that the FDA had updated Tysabri safety information to include information about cases of PML. In the update, the FDA said that the overall rate of Tysabri patients developing PML remains below the one-in-1,000 rate implied on the label. However, the agency warned that this risk “appears to increase with the number of Tysabri infusions received” and that the average number of infusions received before the diagnosis of PML was 25. The rate of PML in patients who have received at least 24 Tysabri infusions ranges from 0.4 to 1.3 per 1,000 patients, the FDA said. The safety information update did not include any labeling changes.
According to The Wall Street Journal, Biogen Idec Inc. and Elan PLC, the makers of Tysabri, and the FDA are now discussing potential label changes to reflect increased PML risk with longer-term usage.