Out of the 124 reported cases of PML in MS Tysabri patients, 23 patients have died to date. Click for larger image:
Printed below is the press release as published on the Multiple Sclerosis Resource Centre's website:
1 death and 13 more cases of PML in Tysabri MS Patients
Biogen Idec Inc. reported 13 more cases of a rare brain infection occurring in multiple-sclerosis patients taking the drug Tysabri, sold with Elan Corp, bringing the affected patients to 124 as of May 4.
The Weston, Mass., biotech company said there was one more death among those patients, bringing total deaths to 23.
The incidence of the infection--progressive multifocal leukoencephalopathy, or PML--is updated monthly and is closely watched.
Tysabri is seen as a highly effective medicine for the debilitating condition, but it is mostly used for patients that have stopped responding to other MS drugs or have particularly aggressive cases. Biogen is developing a blood test for antibodies to a specific virus, JC virus, something that may better determine the chances of patients contracting PML. The test received CE Mark approval in Europe earlier this year and the companies are conducting large studies of its effectiveness.
Many people carry JC virus and it causes no harm, but some biologic drugs that modulate the immune system, including Tysabri, appear to promote activation of JC virus in some patients, leading to PML.
European regulators recently recommended Tysabri's label include language indicating that JC virus antibody status is a PML risk factor. In the U.S., Biogen and Elan have proposed making a similar change. The U.S. label was updated last month to include the updated incidence of PML. Regulators monitor cases of PML as they occur and have said that the benefits of the medicine outweigh the risks.
Tysabri was withdrawn from the market in 2005 and relaunched in 2006--because of its effectiveness--with a strict access plan that regularly monitors patients. The overall global PML rate is now at 1.44 per 1,000 patients. Of the total PML cases, 49 were in the U.S., 69 were in the European Union and six in other areas. The risk of the infection generally increases with the number of monthly intravenous infusions that a patient receives, but that rate drops after 30 months.
Biogen is studying this apparent decrease, warning that there is limited information from patients on the drug longer than 36 months.
The most-recent data translate to a rate of 2.18 cases per 1,000 patients on the drug for a year or longer, rising to 2.76 per 1,000 for those on the drug for two years or longer, and dropping to 1.6 for more than three years. Looked at another way, the rate is about 1.89 cases per 1,000 patients on the drug for between two and three years. The incidence is about 0.49 case per 1,000 patients in those using it for one to two years, and it is essentially nonexistent in patients using it for less than a year.
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