Another Tysabri Patient Stricken with PMLJun 15, 2009 | Parker Waichman LLP
Tysabri, a drug used to treat multiple sclerosis, has been linked to another case of progressive multifocal leukoencephalopathy, or PML. According to a report on Reuters.com, this latest case of Tysabri-associated PML was confirmed on June 10.
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.
According to The Wall Street Journal, Biogen Idec has been posting a PML case update on the Internet every Friday. That will continue until July 24 - the third anniversary of the drug's relaunch - by which time it expects the risk/benefit profile of Tysabri to be clearer. This is the eighth case of Tysabri-associated PML reported by Biogen Idec in the past year.
Like all but two of those PML cases, this latest occurred in a patient overseas, the Journal said. Biogen Idec said this latest patient took 35 doses of the monthly medication, the most of any of the post-launch cases. According to The Wall Street Journal, some believe that duration of Tysabri therapy plays a role in the drug's PML risk.
Last August, Biogen Idec announced that Tysabri had been associated with two other European cases of PML. One patient had been taking Tysabri for 14 months and the other for 17. But unlike others stricken with PML, those patients had been taking Tysabri as monotherapy - with no other drugs. It had been theorized that patients contracting PML had done so because of exposure to multiple medications and that monotherapy with Tysabri was less risky.
At that time the U.S. Food & Drug Administration (FDA) said it was working with the manufacturers of Tysabri to amend the product labeling to inform prescribers and patients that cases of PML have occurred in patients taking Tysabri as monotherapy.
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. People with a weakened immune system or people taking drugs that suppress their immune system (immunosuppressants) are most likely to get the disease. Symptoms include vision problems, loss of coordination, and memory loss. Patients who survive the disease are often permanently disabled.
Earlier this month, we reported that the 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.