Two more Tysabri patients have developed progressive multifocal leukoencephalopathy or PML. Both new cases occurred in European patients, according to a Wall Street Journal report.
Tysabri was taken off the market in 2005 in the U.S. 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.
These are the first cases of PML linked to Tysabri since the drug’s maker stopped providing regular weekly PML updates in July, The Wall Street Journal said. When the updates stopped, 11 cases of the diseases had been reported among Tysabri patients. One of the new PML cases was reported last week in the New England Journal of Medicine. The second was reported the European Committee for Treatment and Research in Multiple Sclerosis that ended Saturday, the Journal said.
Biogen Idec has not confirmed these additional PML cases, and according to the Journal will not confirm additional cases as long as the PML rate is consistent with the rate of one-in-1,000 patients implied by the label.
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.
People with a weakened immune system or people taking drugs that suppress their immune system (immunosuppressants) are most likely to get the disease. Over the summer, we reported that the Food & Drug Administration (FDA) was looking into a link between the lymphoma drug, Rituxan, and the disease. In April, the psoriasis drug Raptiva was voluntary withdrawn from the market after three patients died from PML.
It has been theorized that long-term treatment with Tysabri may increase PML risks, and some doctors have begun having patients take a “holiday” from the drug in an attempt to mitigate risks.