Tysabri and PML Treatment
In previous posts, I have discussed the risk factors and the diagnosis of PML in patients who take Tysabri. Here, I will discuss the treatment for PML in such patients. Unfortunately, there is relatively little to do to directly treat the infection.
The first step recommended to treat a possible PML infection is to try to remove Tysabri from a patient’s bloodstream. This is done via a procedure known as plasmapheresis which requires that patients be admitted to the hospital. It is an old treatment, used for a variety of conditions (including relapses in MS) where antibodies need to be removed from someone’s blood. In this procedure, a large intravenous line is placed, filtering the patient’s blood through a machine that separates the blood cells from other components in the bloodstream. This effectively removes Tysabri from the body allowing for the immune system to recover. It is usually done for 5 days, and each treatment takes several hours.
There are some risks to the procedure. The placement of the catheter itself carries a risk for infection and for a collapsed lung (though this is quite rare). Prior to each treatment, certain blood tests have to be done to make sure that there are no deficits of the blood’s coagulation proteins. During the procedure, a patient’s blood pressure will be carefully monitored and the procedure stopped if the blood pressure falls too low.
Currently, there are no FDA-approved medications that target the JC virus directly. There have been some reports of successful treatment in a small number of patients with other antiviral agents, antimalarial agents, and chemotherapeutic agents. In December 2010, a patient with PML underwent treatment with two medications that sound like they come from a science fiction movie: recombinant human interleukin-7 and CMX001, an antiviral drug. These treatments certainly need to be studied in larger groups of people before they can become a standard treatment for PML.
One encouraging sign is that unlike the course of PML in patients with AIDS, a fair number of Tysabri patients with PML have been able survive the infection with relatively little disability. This seems to be the case for more recent cases of PML now that neurologists are on high alert against the infection and stop Tysabri as soon as it is suspected. Many cases of PML are now being picked up on MRI scans, before patients develop any clinical symptoms of the illness. Clearly, PML is a disease to be feared. Hopefully in the future we will be able to better predict who is at risk for this illness and will also have improved treatments.
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