Some people don’t understand why pharmaceutical companies shouldn’t be allowed to engage in off-label marketing.  Here’s one reason:

Peetz was diagnosed with the autoimmune disorder thrombotic thrombocytopenia purpura in 1995, at age 11. According to the lawsuit, by 2003 Genentech and Biogen Idec were marketing Rituxan as an off-label treatment for Peetz’ condition, meaning the Food and Drug Administration had not approved it for that use.

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Peetz took Rituxan for two years before developing a near-fatal viral infection that left him "a ventilator-dependent flaccid quadriplegic," the lawsuit said. Peetz’ court filing said the drug puts all users at risk, not just those taking it for off-label conditions

Source: Omaha man sues makers of drug Rituxan – San Jose Mercury News

I haven’t had a chance to take a look at the label for Rituxan, so I can’t comment on whether I think there’s a valid failure-to-warn claim there or not.