PML, if you recall, was implicated in the multiple deaths associated with Tysabri last year, leading to its temporary suspension. After much analysis and an unprecedented patient board hearing by the FDA...

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...Tysabri has been brought back but only under intense scrutiny-- designed to detect PML at its earliest stages until the cause is better understood.

Rituxan destroys the body's B-cells, a component of the immune system, with the idea that they will regenerate free of their previous issues, be it cancer or sponsoring another autoimmune condition like rheumatoid arthritis. In the two recent cases, Rituxan was being used to treat Lupus, another autoimmune condition, on an off-label basis. Today Rituxan is only approved to treat Rheumatoid Arthritis and Non-Hodgkins Lymphoma, but it is in trials for lupus as well as cancer and Multiple Sclerosis (Phase II/III for PPMS and Phase II for RRMS).

Note that in its indication for Lymphoma, there have already been *23* cases of PML, and the labeling includes a warning for it. Biogen commented that PML has been seen in cancer and lupus patients who are not being treated with Rituxan as well. Many in the MS community came away from the Tysabri-Avonex-PML debacle thinking that PML, aside from severely immuno-compromised HIV patients, was first seen in our community. Instead, it comes to light over time that this disease is seen in many patient populations where the background of hte disease process is abnormal regulation of the immune system, perhaps in combination with powerful immuno-modulator drugs.