Feb 03, 2009
Study Reports That Plasma Exchange Can Clear Tysabri from Blood; No Evidence Yet That This Can Help Treat PML
In a small study of 12 people with MS who were taking Tysabri® (natalizumab, Biogen Idec, Inc and Elan Pharmaceuticals), Drs. Robert Fox (Cleveland Clinic), B. Khatri and colleagues found that plasma exchange (a blood-cleansing process that involves removing and replacing the liquid portion of blood) could rapidly reduce the concentration of Tysabri in the blood. The study appears in the February 3, 2009 issue of Neurology.
The study was financed by Tysabri’s sponsors to explore whether plasma exchange could serve as an intervention in case an individual develops PML while taking the drug, although the participants in this small study did not have PML. PML (progressive multifocal leukoencephalopathy) is an often fatal brain disease that has occurred in some people who have taken Tysabri. There is no treatment for PML other than to allow the immune system to reconstitute itself. The rationale for this study is that if Tysabri can be cleared from the system more quickly, this may allow immune responses to reconstitute more quickly.
Each participant received an infusion of Tysabri, then 10 to 14 days later underwent three sessions of plasma exchange over five to eight days. One week after the final session, Tysabri concentration had decreased by an average of 92% compared with levels before plasma exchange. Plasma exchange was well tolerated, and there was no increase in MS disease activity. All patients returned to Tysabri treatment without complications.
In some cases following the use of plasma exchange, the reconstitution of immune function may lead to a syndrome known as IRIS (immune reconstitution inflammatory syndrome), which can transiently worsen neurological function. This worsening can be difficult to distinguish from worsening MS or symptoms related to PML. There have been too few instances in which plasma exchange has been used in people who developed PML after taking Tysabri to understand the risks and benefits of plasma exchange in these circumstances, and it is not possible to determine from this study whether plasma exchange is an effective intervention for PML. However, results of this study have been added to the prescribing information.
Use the following link to Biogen Idec's Web site for a company-released update on worldwide Tysabri use and postmarketing cases of PML.
Tysabri is a registered trademark of Biogen Idec and Elan.