Multiple Sclerosis : Tysabri PML Updates Set to Start Again

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. Unfortunately, it also poses serious risks because of its association with PML. 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.

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 MS or Crohn’s Disease 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.

In September, the U.S. Food & Drug Administration (FDA) revealed that 24 cases of PML had been reported in Tysabri users, more than double the 11 Biogen Idec had disclosed at its final monthly update in July. As of mid-January, the number of PML cases among people treated with Tysabri stands at 31.